Download Anna University B-Tech 1st Year First Year BS8161 Physics Lab Manual Question Paper

Download Anna University B.Tech/BE (Bachelor of Technology) 1st Year (First Year) First Year BS8161 Physics Lab Manual Question Paper.




?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
2


PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science and fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems and use this knowledge to acquire
higher education.
2. Core competence
To train the students in Engineering Physics so as to apply their knowledge and training to compare,
and to analyze various engineering industrial problems for finding solutions.
3. Breadth
To provide relevant training and experience to bridge the gap between theoretical learning and
practice that enables them to find solutions for the real time problems in industry and to design products.
4. Professionalism
To inculcate professional and effective communication skills, leadership qualities and team spirit for
the students to make them multi-faceted personalities and develop their ability to relate engineering issues
to broader social context.
5. Lifelong learning/ethics
To demonstrate and practice ethical and professional responsibilities in the industry and society by
and large, through commitment and lifelong learning needed for successful professional career.





FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
2


PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science and fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems and use this knowledge to acquire
higher education.
2. Core competence
To train the students in Engineering Physics so as to apply their knowledge and training to compare,
and to analyze various engineering industrial problems for finding solutions.
3. Breadth
To provide relevant training and experience to bridge the gap between theoretical learning and
practice that enables them to find solutions for the real time problems in industry and to design products.
4. Professionalism
To inculcate professional and effective communication skills, leadership qualities and team spirit for
the students to make them multi-faceted personalities and develop their ability to relate engineering issues
to broader social context.
5. Lifelong learning/ethics
To demonstrate and practice ethical and professional responsibilities in the industry and society by
and large, through commitment and lifelong learning needed for successful professional career.





3


PROGRAMME OUTCOMES (POs)

a) To demonstrate and apply knowledge of Mathematics, Science and Engineering fundamentals in
Engineering physics
b) To determine the Moment of Inertia of given disc and Rigidity modulus of the given wire using
Torsional Pendulum
c) To determine Young?s modulus of a given bar using Non-Uniform bending
d) To utilize laser source and grating to estimate the wave length, particle size of given powder and
Numerical Aperture & acceptance angle of given optical fiber
e) To find the Thermal conductivity of a bad conductor using Lee?s Disc method
f) To Measure the velocity of ultrasonic wave in a liquid and compressibility of the liquid usingultrasonic
Interferometer
g) To determine the wavelength of Hg source using grating and spectrometer
h) To find the thickness of a thin wire using Air- wedge method
i) To participate and succeed in competitive exams and visualize and work on laboratory and
multidisciplinary tasks











FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
2


PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science and fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems and use this knowledge to acquire
higher education.
2. Core competence
To train the students in Engineering Physics so as to apply their knowledge and training to compare,
and to analyze various engineering industrial problems for finding solutions.
3. Breadth
To provide relevant training and experience to bridge the gap between theoretical learning and
practice that enables them to find solutions for the real time problems in industry and to design products.
4. Professionalism
To inculcate professional and effective communication skills, leadership qualities and team spirit for
the students to make them multi-faceted personalities and develop their ability to relate engineering issues
to broader social context.
5. Lifelong learning/ethics
To demonstrate and practice ethical and professional responsibilities in the industry and society by
and large, through commitment and lifelong learning needed for successful professional career.





3


PROGRAMME OUTCOMES (POs)

a) To demonstrate and apply knowledge of Mathematics, Science and Engineering fundamentals in
Engineering physics
b) To determine the Moment of Inertia of given disc and Rigidity modulus of the given wire using
Torsional Pendulum
c) To determine Young?s modulus of a given bar using Non-Uniform bending
d) To utilize laser source and grating to estimate the wave length, particle size of given powder and
Numerical Aperture & acceptance angle of given optical fiber
e) To find the Thermal conductivity of a bad conductor using Lee?s Disc method
f) To Measure the velocity of ultrasonic wave in a liquid and compressibility of the liquid usingultrasonic
Interferometer
g) To determine the wavelength of Hg source using grating and spectrometer
h) To find the thickness of a thin wire using Air- wedge method
i) To participate and succeed in competitive exams and visualize and work on laboratory and
multidisciplinary tasks











4


BS 8161 ? PHYSICSLABORATORY
(Common to all branches of B.E. / B.TechProgrammes)
SYLLABUS


To introduce different experiments to test basic understanding of physics concepts applied in optics, thermal
physics, properties of matter and liquids.

LIST OF EXPERIMENTS: PHYSICS LABORATORY(Any 5 Experiments)
1. Determination of Rigidity modulus ? Torsion pendulum
2. Determination of Young? s modulus by Non uniform bending method
3. (a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
4. Determination of thermal conductivity of a bad conductor ? Lee?s Disc method.
5. Determination of velocity of sound and compressibility of liquid ? Ultrasonic interferometer
6. Determination of wavelength of mercury spectrum ? spectrometer grating
7. Determination of band gap of a semiconductor
8. Determination of thickness of a thin wire ? Air wedge method




Completion of the course, the students will be able to: apply physics principles of optics and thermal physics
to evaluate engineering properties of materials.


COURSE OUTCOMES
COURSE OBJECTIVES
FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
2


PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science and fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems and use this knowledge to acquire
higher education.
2. Core competence
To train the students in Engineering Physics so as to apply their knowledge and training to compare,
and to analyze various engineering industrial problems for finding solutions.
3. Breadth
To provide relevant training and experience to bridge the gap between theoretical learning and
practice that enables them to find solutions for the real time problems in industry and to design products.
4. Professionalism
To inculcate professional and effective communication skills, leadership qualities and team spirit for
the students to make them multi-faceted personalities and develop their ability to relate engineering issues
to broader social context.
5. Lifelong learning/ethics
To demonstrate and practice ethical and professional responsibilities in the industry and society by
and large, through commitment and lifelong learning needed for successful professional career.





3


PROGRAMME OUTCOMES (POs)

a) To demonstrate and apply knowledge of Mathematics, Science and Engineering fundamentals in
Engineering physics
b) To determine the Moment of Inertia of given disc and Rigidity modulus of the given wire using
Torsional Pendulum
c) To determine Young?s modulus of a given bar using Non-Uniform bending
d) To utilize laser source and grating to estimate the wave length, particle size of given powder and
Numerical Aperture & acceptance angle of given optical fiber
e) To find the Thermal conductivity of a bad conductor using Lee?s Disc method
f) To Measure the velocity of ultrasonic wave in a liquid and compressibility of the liquid usingultrasonic
Interferometer
g) To determine the wavelength of Hg source using grating and spectrometer
h) To find the thickness of a thin wire using Air- wedge method
i) To participate and succeed in competitive exams and visualize and work on laboratory and
multidisciplinary tasks











4


BS 8161 ? PHYSICSLABORATORY
(Common to all branches of B.E. / B.TechProgrammes)
SYLLABUS


To introduce different experiments to test basic understanding of physics concepts applied in optics, thermal
physics, properties of matter and liquids.

LIST OF EXPERIMENTS: PHYSICS LABORATORY(Any 5 Experiments)
1. Determination of Rigidity modulus ? Torsion pendulum
2. Determination of Young? s modulus by Non uniform bending method
3. (a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
4. Determination of thermal conductivity of a bad conductor ? Lee?s Disc method.
5. Determination of velocity of sound and compressibility of liquid ? Ultrasonic interferometer
6. Determination of wavelength of mercury spectrum ? spectrometer grating
7. Determination of band gap of a semiconductor
8. Determination of thickness of a thin wire ? Air wedge method




Completion of the course, the students will be able to: apply physics principles of optics and thermal physics
to evaluate engineering properties of materials.


COURSE OUTCOMES
COURSE OBJECTIVES
5

BS 8161 ? PHYSICS LABORATORY
CONTENTS

Sl.No. Name of the Experiment (any 5 experiments)
Page
No.
1.
Determination of Rigidity modulus ? Torsion pendulum
6
2.
Determination of Young ?s modulus by Non uniform bending method
12
3.
(a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
18
4.
Determination of thermal conductivity of a bad conductor ? Lee ?s Disc method.
28
5.
Determination of velocity of sound and compressibility of liquid ? Ultrasonic
interferometer
37
6.
Determination of wavelength of mercury spectrum ? spectrometer grating
42
7.
Determination of thickness of a thin wire ? Air wedge method
48
MEASURING INSTRUMENTS
M1 Screw gauge 54
M2 Vernier Calipers 58
M3 Travelling Microscope 62
M4 Spectrometer 66








FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
2


PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science and fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems and use this knowledge to acquire
higher education.
2. Core competence
To train the students in Engineering Physics so as to apply their knowledge and training to compare,
and to analyze various engineering industrial problems for finding solutions.
3. Breadth
To provide relevant training and experience to bridge the gap between theoretical learning and
practice that enables them to find solutions for the real time problems in industry and to design products.
4. Professionalism
To inculcate professional and effective communication skills, leadership qualities and team spirit for
the students to make them multi-faceted personalities and develop their ability to relate engineering issues
to broader social context.
5. Lifelong learning/ethics
To demonstrate and practice ethical and professional responsibilities in the industry and society by
and large, through commitment and lifelong learning needed for successful professional career.





3


PROGRAMME OUTCOMES (POs)

a) To demonstrate and apply knowledge of Mathematics, Science and Engineering fundamentals in
Engineering physics
b) To determine the Moment of Inertia of given disc and Rigidity modulus of the given wire using
Torsional Pendulum
c) To determine Young?s modulus of a given bar using Non-Uniform bending
d) To utilize laser source and grating to estimate the wave length, particle size of given powder and
Numerical Aperture & acceptance angle of given optical fiber
e) To find the Thermal conductivity of a bad conductor using Lee?s Disc method
f) To Measure the velocity of ultrasonic wave in a liquid and compressibility of the liquid usingultrasonic
Interferometer
g) To determine the wavelength of Hg source using grating and spectrometer
h) To find the thickness of a thin wire using Air- wedge method
i) To participate and succeed in competitive exams and visualize and work on laboratory and
multidisciplinary tasks











4


BS 8161 ? PHYSICSLABORATORY
(Common to all branches of B.E. / B.TechProgrammes)
SYLLABUS


To introduce different experiments to test basic understanding of physics concepts applied in optics, thermal
physics, properties of matter and liquids.

LIST OF EXPERIMENTS: PHYSICS LABORATORY(Any 5 Experiments)
1. Determination of Rigidity modulus ? Torsion pendulum
2. Determination of Young? s modulus by Non uniform bending method
3. (a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
4. Determination of thermal conductivity of a bad conductor ? Lee?s Disc method.
5. Determination of velocity of sound and compressibility of liquid ? Ultrasonic interferometer
6. Determination of wavelength of mercury spectrum ? spectrometer grating
7. Determination of band gap of a semiconductor
8. Determination of thickness of a thin wire ? Air wedge method




Completion of the course, the students will be able to: apply physics principles of optics and thermal physics
to evaluate engineering properties of materials.


COURSE OUTCOMES
COURSE OBJECTIVES
5

BS 8161 ? PHYSICS LABORATORY
CONTENTS

Sl.No. Name of the Experiment (any 5 experiments)
Page
No.
1.
Determination of Rigidity modulus ? Torsion pendulum
6
2.
Determination of Young ?s modulus by Non uniform bending method
12
3.
(a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
18
4.
Determination of thermal conductivity of a bad conductor ? Lee ?s Disc method.
28
5.
Determination of velocity of sound and compressibility of liquid ? Ultrasonic
interferometer
37
6.
Determination of wavelength of mercury spectrum ? spectrometer grating
42
7.
Determination of thickness of a thin wire ? Air wedge method
48
MEASURING INSTRUMENTS
M1 Screw gauge 54
M2 Vernier Calipers 58
M3 Travelling Microscope 62
M4 Spectrometer 66








6

TORSIONAL PENDULUM










FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
2


PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science and fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems and use this knowledge to acquire
higher education.
2. Core competence
To train the students in Engineering Physics so as to apply their knowledge and training to compare,
and to analyze various engineering industrial problems for finding solutions.
3. Breadth
To provide relevant training and experience to bridge the gap between theoretical learning and
practice that enables them to find solutions for the real time problems in industry and to design products.
4. Professionalism
To inculcate professional and effective communication skills, leadership qualities and team spirit for
the students to make them multi-faceted personalities and develop their ability to relate engineering issues
to broader social context.
5. Lifelong learning/ethics
To demonstrate and practice ethical and professional responsibilities in the industry and society by
and large, through commitment and lifelong learning needed for successful professional career.





3


PROGRAMME OUTCOMES (POs)

a) To demonstrate and apply knowledge of Mathematics, Science and Engineering fundamentals in
Engineering physics
b) To determine the Moment of Inertia of given disc and Rigidity modulus of the given wire using
Torsional Pendulum
c) To determine Young?s modulus of a given bar using Non-Uniform bending
d) To utilize laser source and grating to estimate the wave length, particle size of given powder and
Numerical Aperture & acceptance angle of given optical fiber
e) To find the Thermal conductivity of a bad conductor using Lee?s Disc method
f) To Measure the velocity of ultrasonic wave in a liquid and compressibility of the liquid usingultrasonic
Interferometer
g) To determine the wavelength of Hg source using grating and spectrometer
h) To find the thickness of a thin wire using Air- wedge method
i) To participate and succeed in competitive exams and visualize and work on laboratory and
multidisciplinary tasks











4


BS 8161 ? PHYSICSLABORATORY
(Common to all branches of B.E. / B.TechProgrammes)
SYLLABUS


To introduce different experiments to test basic understanding of physics concepts applied in optics, thermal
physics, properties of matter and liquids.

LIST OF EXPERIMENTS: PHYSICS LABORATORY(Any 5 Experiments)
1. Determination of Rigidity modulus ? Torsion pendulum
2. Determination of Young? s modulus by Non uniform bending method
3. (a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
4. Determination of thermal conductivity of a bad conductor ? Lee?s Disc method.
5. Determination of velocity of sound and compressibility of liquid ? Ultrasonic interferometer
6. Determination of wavelength of mercury spectrum ? spectrometer grating
7. Determination of band gap of a semiconductor
8. Determination of thickness of a thin wire ? Air wedge method




Completion of the course, the students will be able to: apply physics principles of optics and thermal physics
to evaluate engineering properties of materials.


COURSE OUTCOMES
COURSE OBJECTIVES
5

BS 8161 ? PHYSICS LABORATORY
CONTENTS

Sl.No. Name of the Experiment (any 5 experiments)
Page
No.
1.
Determination of Rigidity modulus ? Torsion pendulum
6
2.
Determination of Young ?s modulus by Non uniform bending method
12
3.
(a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
18
4.
Determination of thermal conductivity of a bad conductor ? Lee ?s Disc method.
28
5.
Determination of velocity of sound and compressibility of liquid ? Ultrasonic
interferometer
37
6.
Determination of wavelength of mercury spectrum ? spectrometer grating
42
7.
Determination of thickness of a thin wire ? Air wedge method
48
MEASURING INSTRUMENTS
M1 Screw gauge 54
M2 Vernier Calipers 58
M3 Travelling Microscope 62
M4 Spectrometer 66








6

TORSIONAL PENDULUM










7

Expt. No.1 TORSIONAL PENDULUM

AIM:
To determine the moment of inertia of the given disc and hence to determine the rigidity modulus of
the material of the given suspension wire by torsional oscillations
APPARATUS REQUIRED:
Torsional pendulum, two equal masses, stop clock, screw gauge and meter scale

FORMULA:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
where
m ?mass of the cylinder placed on the disc (kg)
To ?period of the pendulum for a length of l without mass (s)
T1?period of the pendulum for the same length when mass m is placed at a distance d 1
from the center of the suspension wire (s)
T2?period of the pendulum for the same length when mass m is placed at a distance d 2
from the center of the suspension wire (s)
a ? radius of the suspension wire (m)




FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
2


PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science and fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems and use this knowledge to acquire
higher education.
2. Core competence
To train the students in Engineering Physics so as to apply their knowledge and training to compare,
and to analyze various engineering industrial problems for finding solutions.
3. Breadth
To provide relevant training and experience to bridge the gap between theoretical learning and
practice that enables them to find solutions for the real time problems in industry and to design products.
4. Professionalism
To inculcate professional and effective communication skills, leadership qualities and team spirit for
the students to make them multi-faceted personalities and develop their ability to relate engineering issues
to broader social context.
5. Lifelong learning/ethics
To demonstrate and practice ethical and professional responsibilities in the industry and society by
and large, through commitment and lifelong learning needed for successful professional career.





3


PROGRAMME OUTCOMES (POs)

a) To demonstrate and apply knowledge of Mathematics, Science and Engineering fundamentals in
Engineering physics
b) To determine the Moment of Inertia of given disc and Rigidity modulus of the given wire using
Torsional Pendulum
c) To determine Young?s modulus of a given bar using Non-Uniform bending
d) To utilize laser source and grating to estimate the wave length, particle size of given powder and
Numerical Aperture & acceptance angle of given optical fiber
e) To find the Thermal conductivity of a bad conductor using Lee?s Disc method
f) To Measure the velocity of ultrasonic wave in a liquid and compressibility of the liquid usingultrasonic
Interferometer
g) To determine the wavelength of Hg source using grating and spectrometer
h) To find the thickness of a thin wire using Air- wedge method
i) To participate and succeed in competitive exams and visualize and work on laboratory and
multidisciplinary tasks











4


BS 8161 ? PHYSICSLABORATORY
(Common to all branches of B.E. / B.TechProgrammes)
SYLLABUS


To introduce different experiments to test basic understanding of physics concepts applied in optics, thermal
physics, properties of matter and liquids.

LIST OF EXPERIMENTS: PHYSICS LABORATORY(Any 5 Experiments)
1. Determination of Rigidity modulus ? Torsion pendulum
2. Determination of Young? s modulus by Non uniform bending method
3. (a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
4. Determination of thermal conductivity of a bad conductor ? Lee?s Disc method.
5. Determination of velocity of sound and compressibility of liquid ? Ultrasonic interferometer
6. Determination of wavelength of mercury spectrum ? spectrometer grating
7. Determination of band gap of a semiconductor
8. Determination of thickness of a thin wire ? Air wedge method




Completion of the course, the students will be able to: apply physics principles of optics and thermal physics
to evaluate engineering properties of materials.


COURSE OUTCOMES
COURSE OBJECTIVES
5

BS 8161 ? PHYSICS LABORATORY
CONTENTS

Sl.No. Name of the Experiment (any 5 experiments)
Page
No.
1.
Determination of Rigidity modulus ? Torsion pendulum
6
2.
Determination of Young ?s modulus by Non uniform bending method
12
3.
(a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
18
4.
Determination of thermal conductivity of a bad conductor ? Lee ?s Disc method.
28
5.
Determination of velocity of sound and compressibility of liquid ? Ultrasonic
interferometer
37
6.
Determination of wavelength of mercury spectrum ? spectrometer grating
42
7.
Determination of thickness of a thin wire ? Air wedge method
48
MEASURING INSTRUMENTS
M1 Screw gauge 54
M2 Vernier Calipers 58
M3 Travelling Microscope 62
M4 Spectrometer 66








6

TORSIONAL PENDULUM










7

Expt. No.1 TORSIONAL PENDULUM

AIM:
To determine the moment of inertia of the given disc and hence to determine the rigidity modulus of
the material of the given suspension wire by torsional oscillations
APPARATUS REQUIRED:
Torsional pendulum, two equal masses, stop clock, screw gauge and meter scale

FORMULA:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
where
m ?mass of the cylinder placed on the disc (kg)
To ?period of the pendulum for a length of l without mass (s)
T1?period of the pendulum for the same length when mass m is placed at a distance d 1
from the center of the suspension wire (s)
T2?period of the pendulum for the same length when mass m is placed at a distance d 2
from the center of the suspension wire (s)
a ? radius of the suspension wire (m)




8

1. To determine the time period of the disc:
Length of the wire (l)= --------
2
10
?
? m
Position of the equal
masses
Time for 10 oscillations Time period
(one oscillation)
s
Trial-1
s
Trial-2
s
Mean
s
Without any masses T0
With masses at
d1 = x10
-2
m
T1
With masses at
d2 = x10
-2
m
T2

2. To determine the radius of the wire:
Least count =0 .01 mm. Zero Error ZE = --------- divisions
Zero Correction ZC = ---------- mm

Sl.No.
Pitch Scale
Reading
PSR
3
10
?
? m
Head Scale
Coincidence
HSC
div
Observed reading
OR = PSR + (HSCXLC)
3
10
?
? m
Correct reading
CR = OR ? ZC
3
10
?
? m




Mean = ----------------
3
10
?
? m



FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
2


PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science and fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems and use this knowledge to acquire
higher education.
2. Core competence
To train the students in Engineering Physics so as to apply their knowledge and training to compare,
and to analyze various engineering industrial problems for finding solutions.
3. Breadth
To provide relevant training and experience to bridge the gap between theoretical learning and
practice that enables them to find solutions for the real time problems in industry and to design products.
4. Professionalism
To inculcate professional and effective communication skills, leadership qualities and team spirit for
the students to make them multi-faceted personalities and develop their ability to relate engineering issues
to broader social context.
5. Lifelong learning/ethics
To demonstrate and practice ethical and professional responsibilities in the industry and society by
and large, through commitment and lifelong learning needed for successful professional career.





3


PROGRAMME OUTCOMES (POs)

a) To demonstrate and apply knowledge of Mathematics, Science and Engineering fundamentals in
Engineering physics
b) To determine the Moment of Inertia of given disc and Rigidity modulus of the given wire using
Torsional Pendulum
c) To determine Young?s modulus of a given bar using Non-Uniform bending
d) To utilize laser source and grating to estimate the wave length, particle size of given powder and
Numerical Aperture & acceptance angle of given optical fiber
e) To find the Thermal conductivity of a bad conductor using Lee?s Disc method
f) To Measure the velocity of ultrasonic wave in a liquid and compressibility of the liquid usingultrasonic
Interferometer
g) To determine the wavelength of Hg source using grating and spectrometer
h) To find the thickness of a thin wire using Air- wedge method
i) To participate and succeed in competitive exams and visualize and work on laboratory and
multidisciplinary tasks











4


BS 8161 ? PHYSICSLABORATORY
(Common to all branches of B.E. / B.TechProgrammes)
SYLLABUS


To introduce different experiments to test basic understanding of physics concepts applied in optics, thermal
physics, properties of matter and liquids.

LIST OF EXPERIMENTS: PHYSICS LABORATORY(Any 5 Experiments)
1. Determination of Rigidity modulus ? Torsion pendulum
2. Determination of Young? s modulus by Non uniform bending method
3. (a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
4. Determination of thermal conductivity of a bad conductor ? Lee?s Disc method.
5. Determination of velocity of sound and compressibility of liquid ? Ultrasonic interferometer
6. Determination of wavelength of mercury spectrum ? spectrometer grating
7. Determination of band gap of a semiconductor
8. Determination of thickness of a thin wire ? Air wedge method




Completion of the course, the students will be able to: apply physics principles of optics and thermal physics
to evaluate engineering properties of materials.


COURSE OUTCOMES
COURSE OBJECTIVES
5

BS 8161 ? PHYSICS LABORATORY
CONTENTS

Sl.No. Name of the Experiment (any 5 experiments)
Page
No.
1.
Determination of Rigidity modulus ? Torsion pendulum
6
2.
Determination of Young ?s modulus by Non uniform bending method
12
3.
(a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
18
4.
Determination of thermal conductivity of a bad conductor ? Lee ?s Disc method.
28
5.
Determination of velocity of sound and compressibility of liquid ? Ultrasonic
interferometer
37
6.
Determination of wavelength of mercury spectrum ? spectrometer grating
42
7.
Determination of thickness of a thin wire ? Air wedge method
48
MEASURING INSTRUMENTS
M1 Screw gauge 54
M2 Vernier Calipers 58
M3 Travelling Microscope 62
M4 Spectrometer 66








6

TORSIONAL PENDULUM










7

Expt. No.1 TORSIONAL PENDULUM

AIM:
To determine the moment of inertia of the given disc and hence to determine the rigidity modulus of
the material of the given suspension wire by torsional oscillations
APPARATUS REQUIRED:
Torsional pendulum, two equal masses, stop clock, screw gauge and meter scale

FORMULA:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
where
m ?mass of the cylinder placed on the disc (kg)
To ?period of the pendulum for a length of l without mass (s)
T1?period of the pendulum for the same length when mass m is placed at a distance d 1
from the center of the suspension wire (s)
T2?period of the pendulum for the same length when mass m is placed at a distance d 2
from the center of the suspension wire (s)
a ? radius of the suspension wire (m)




8

1. To determine the time period of the disc:
Length of the wire (l)= --------
2
10
?
? m
Position of the equal
masses
Time for 10 oscillations Time period
(one oscillation)
s
Trial-1
s
Trial-2
s
Mean
s
Without any masses T0
With masses at
d1 = x10
-2
m
T1
With masses at
d2 = x10
-2
m
T2

2. To determine the radius of the wire:
Least count =0 .01 mm. Zero Error ZE = --------- divisions
Zero Correction ZC = ---------- mm

Sl.No.
Pitch Scale
Reading
PSR
3
10
?
? m
Head Scale
Coincidence
HSC
div
Observed reading
OR = PSR + (HSCXLC)
3
10
?
? m
Correct reading
CR = OR ? ZC
3
10
?
? m




Mean = ----------------
3
10
?
? m



9

PROCEDURE:
Torsional pendulum is suspended from vertical chuck. The length of the suspension wire is measured
between the vertical chuck and the chuck attached to the uniform circular disc (i). The circular disc is twisted
slightly without masses on the disc. Now it executes torsional oscillations. Care is taken to see that the disc
oscillates without wobbling. Time taken for 20 oscillations is noted with the help of a stop clock. Two trials are
taken. The average of these two trial readings is calculated from which the period of oscillations is found out
as T0.
Two identical cylindrical masses each of mass m are symmetrically placed on the disc on either side
of the wire at a distance d from the center of the disc. As before the disc is gently twisted. Time taken for 20
oscillations is noted from which the period of oscillation is calculated as T1.
The cylindrical masses are placed at a distance d2 from the center and the experiment is repeated.
The mean time period of oscillations is calculated T2.
The diameter of the specimen wire is measured accurately with the help of the screw gauge, at
various places on the wire. The average diameter and hence the radius of the wire is calculated as r.
Moment of inertia and the rigidity modulus are determined by the substituting the value of m, T 0, T1, T2,
T3, and l in the formula.










FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
2


PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science and fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems and use this knowledge to acquire
higher education.
2. Core competence
To train the students in Engineering Physics so as to apply their knowledge and training to compare,
and to analyze various engineering industrial problems for finding solutions.
3. Breadth
To provide relevant training and experience to bridge the gap between theoretical learning and
practice that enables them to find solutions for the real time problems in industry and to design products.
4. Professionalism
To inculcate professional and effective communication skills, leadership qualities and team spirit for
the students to make them multi-faceted personalities and develop their ability to relate engineering issues
to broader social context.
5. Lifelong learning/ethics
To demonstrate and practice ethical and professional responsibilities in the industry and society by
and large, through commitment and lifelong learning needed for successful professional career.





3


PROGRAMME OUTCOMES (POs)

a) To demonstrate and apply knowledge of Mathematics, Science and Engineering fundamentals in
Engineering physics
b) To determine the Moment of Inertia of given disc and Rigidity modulus of the given wire using
Torsional Pendulum
c) To determine Young?s modulus of a given bar using Non-Uniform bending
d) To utilize laser source and grating to estimate the wave length, particle size of given powder and
Numerical Aperture & acceptance angle of given optical fiber
e) To find the Thermal conductivity of a bad conductor using Lee?s Disc method
f) To Measure the velocity of ultrasonic wave in a liquid and compressibility of the liquid usingultrasonic
Interferometer
g) To determine the wavelength of Hg source using grating and spectrometer
h) To find the thickness of a thin wire using Air- wedge method
i) To participate and succeed in competitive exams and visualize and work on laboratory and
multidisciplinary tasks











4


BS 8161 ? PHYSICSLABORATORY
(Common to all branches of B.E. / B.TechProgrammes)
SYLLABUS


To introduce different experiments to test basic understanding of physics concepts applied in optics, thermal
physics, properties of matter and liquids.

LIST OF EXPERIMENTS: PHYSICS LABORATORY(Any 5 Experiments)
1. Determination of Rigidity modulus ? Torsion pendulum
2. Determination of Young? s modulus by Non uniform bending method
3. (a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
4. Determination of thermal conductivity of a bad conductor ? Lee?s Disc method.
5. Determination of velocity of sound and compressibility of liquid ? Ultrasonic interferometer
6. Determination of wavelength of mercury spectrum ? spectrometer grating
7. Determination of band gap of a semiconductor
8. Determination of thickness of a thin wire ? Air wedge method




Completion of the course, the students will be able to: apply physics principles of optics and thermal physics
to evaluate engineering properties of materials.


COURSE OUTCOMES
COURSE OBJECTIVES
5

BS 8161 ? PHYSICS LABORATORY
CONTENTS

Sl.No. Name of the Experiment (any 5 experiments)
Page
No.
1.
Determination of Rigidity modulus ? Torsion pendulum
6
2.
Determination of Young ?s modulus by Non uniform bending method
12
3.
(a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
18
4.
Determination of thermal conductivity of a bad conductor ? Lee ?s Disc method.
28
5.
Determination of velocity of sound and compressibility of liquid ? Ultrasonic
interferometer
37
6.
Determination of wavelength of mercury spectrum ? spectrometer grating
42
7.
Determination of thickness of a thin wire ? Air wedge method
48
MEASURING INSTRUMENTS
M1 Screw gauge 54
M2 Vernier Calipers 58
M3 Travelling Microscope 62
M4 Spectrometer 66








6

TORSIONAL PENDULUM










7

Expt. No.1 TORSIONAL PENDULUM

AIM:
To determine the moment of inertia of the given disc and hence to determine the rigidity modulus of
the material of the given suspension wire by torsional oscillations
APPARATUS REQUIRED:
Torsional pendulum, two equal masses, stop clock, screw gauge and meter scale

FORMULA:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
where
m ?mass of the cylinder placed on the disc (kg)
To ?period of the pendulum for a length of l without mass (s)
T1?period of the pendulum for the same length when mass m is placed at a distance d 1
from the center of the suspension wire (s)
T2?period of the pendulum for the same length when mass m is placed at a distance d 2
from the center of the suspension wire (s)
a ? radius of the suspension wire (m)




8

1. To determine the time period of the disc:
Length of the wire (l)= --------
2
10
?
? m
Position of the equal
masses
Time for 10 oscillations Time period
(one oscillation)
s
Trial-1
s
Trial-2
s
Mean
s
Without any masses T0
With masses at
d1 = x10
-2
m
T1
With masses at
d2 = x10
-2
m
T2

2. To determine the radius of the wire:
Least count =0 .01 mm. Zero Error ZE = --------- divisions
Zero Correction ZC = ---------- mm

Sl.No.
Pitch Scale
Reading
PSR
3
10
?
? m
Head Scale
Coincidence
HSC
div
Observed reading
OR = PSR + (HSCXLC)
3
10
?
? m
Correct reading
CR = OR ? ZC
3
10
?
? m




Mean = ----------------
3
10
?
? m



9

PROCEDURE:
Torsional pendulum is suspended from vertical chuck. The length of the suspension wire is measured
between the vertical chuck and the chuck attached to the uniform circular disc (i). The circular disc is twisted
slightly without masses on the disc. Now it executes torsional oscillations. Care is taken to see that the disc
oscillates without wobbling. Time taken for 20 oscillations is noted with the help of a stop clock. Two trials are
taken. The average of these two trial readings is calculated from which the period of oscillations is found out
as T0.
Two identical cylindrical masses each of mass m are symmetrically placed on the disc on either side
of the wire at a distance d from the center of the disc. As before the disc is gently twisted. Time taken for 20
oscillations is noted from which the period of oscillation is calculated as T1.
The cylindrical masses are placed at a distance d2 from the center and the experiment is repeated.
The mean time period of oscillations is calculated T2.
The diameter of the specimen wire is measured accurately with the help of the screw gauge, at
various places on the wire. The average diameter and hence the radius of the wire is calculated as r.
Moment of inertia and the rigidity modulus are determined by the substituting the value of m, T 0, T1, T2,
T3, and l in the formula.










10

CALCULATION:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2

Mass of cylindrical mass, m = ----------- ? 10
-3
kg
Closest distance of the mass from the centre of the suspension wire, d1 = ------------ ? 10
-2
m
Farthest distance of the mass from the centre of suspension wire, d2= ------------? 10
-2
m
Period of oscillation without mass, To = ------------- s
Period of oscillation with mass at d1, T1= ------------ s
Period of oscillation with mass at d2, T2 = ------------- s

Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
= --------------- kg m
2
= --------------- kg m
2

Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
Moment of inertia, I = ------------------ kg m
2
Length of the wire, l = ------------------- ? 10
-2
m
Time of oscillation, To = ------------------ s
Radius of the wire, a = ------------------- ? 10
-3
m
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
= ----------------------
Rigidity modulus, n = ------------------- Nm
-2
FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
2


PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science and fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems and use this knowledge to acquire
higher education.
2. Core competence
To train the students in Engineering Physics so as to apply their knowledge and training to compare,
and to analyze various engineering industrial problems for finding solutions.
3. Breadth
To provide relevant training and experience to bridge the gap between theoretical learning and
practice that enables them to find solutions for the real time problems in industry and to design products.
4. Professionalism
To inculcate professional and effective communication skills, leadership qualities and team spirit for
the students to make them multi-faceted personalities and develop their ability to relate engineering issues
to broader social context.
5. Lifelong learning/ethics
To demonstrate and practice ethical and professional responsibilities in the industry and society by
and large, through commitment and lifelong learning needed for successful professional career.





3


PROGRAMME OUTCOMES (POs)

a) To demonstrate and apply knowledge of Mathematics, Science and Engineering fundamentals in
Engineering physics
b) To determine the Moment of Inertia of given disc and Rigidity modulus of the given wire using
Torsional Pendulum
c) To determine Young?s modulus of a given bar using Non-Uniform bending
d) To utilize laser source and grating to estimate the wave length, particle size of given powder and
Numerical Aperture & acceptance angle of given optical fiber
e) To find the Thermal conductivity of a bad conductor using Lee?s Disc method
f) To Measure the velocity of ultrasonic wave in a liquid and compressibility of the liquid usingultrasonic
Interferometer
g) To determine the wavelength of Hg source using grating and spectrometer
h) To find the thickness of a thin wire using Air- wedge method
i) To participate and succeed in competitive exams and visualize and work on laboratory and
multidisciplinary tasks











4


BS 8161 ? PHYSICSLABORATORY
(Common to all branches of B.E. / B.TechProgrammes)
SYLLABUS


To introduce different experiments to test basic understanding of physics concepts applied in optics, thermal
physics, properties of matter and liquids.

LIST OF EXPERIMENTS: PHYSICS LABORATORY(Any 5 Experiments)
1. Determination of Rigidity modulus ? Torsion pendulum
2. Determination of Young? s modulus by Non uniform bending method
3. (a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
4. Determination of thermal conductivity of a bad conductor ? Lee?s Disc method.
5. Determination of velocity of sound and compressibility of liquid ? Ultrasonic interferometer
6. Determination of wavelength of mercury spectrum ? spectrometer grating
7. Determination of band gap of a semiconductor
8. Determination of thickness of a thin wire ? Air wedge method




Completion of the course, the students will be able to: apply physics principles of optics and thermal physics
to evaluate engineering properties of materials.


COURSE OUTCOMES
COURSE OBJECTIVES
5

BS 8161 ? PHYSICS LABORATORY
CONTENTS

Sl.No. Name of the Experiment (any 5 experiments)
Page
No.
1.
Determination of Rigidity modulus ? Torsion pendulum
6
2.
Determination of Young ?s modulus by Non uniform bending method
12
3.
(a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
18
4.
Determination of thermal conductivity of a bad conductor ? Lee ?s Disc method.
28
5.
Determination of velocity of sound and compressibility of liquid ? Ultrasonic
interferometer
37
6.
Determination of wavelength of mercury spectrum ? spectrometer grating
42
7.
Determination of thickness of a thin wire ? Air wedge method
48
MEASURING INSTRUMENTS
M1 Screw gauge 54
M2 Vernier Calipers 58
M3 Travelling Microscope 62
M4 Spectrometer 66








6

TORSIONAL PENDULUM










7

Expt. No.1 TORSIONAL PENDULUM

AIM:
To determine the moment of inertia of the given disc and hence to determine the rigidity modulus of
the material of the given suspension wire by torsional oscillations
APPARATUS REQUIRED:
Torsional pendulum, two equal masses, stop clock, screw gauge and meter scale

FORMULA:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
where
m ?mass of the cylinder placed on the disc (kg)
To ?period of the pendulum for a length of l without mass (s)
T1?period of the pendulum for the same length when mass m is placed at a distance d 1
from the center of the suspension wire (s)
T2?period of the pendulum for the same length when mass m is placed at a distance d 2
from the center of the suspension wire (s)
a ? radius of the suspension wire (m)




8

1. To determine the time period of the disc:
Length of the wire (l)= --------
2
10
?
? m
Position of the equal
masses
Time for 10 oscillations Time period
(one oscillation)
s
Trial-1
s
Trial-2
s
Mean
s
Without any masses T0
With masses at
d1 = x10
-2
m
T1
With masses at
d2 = x10
-2
m
T2

2. To determine the radius of the wire:
Least count =0 .01 mm. Zero Error ZE = --------- divisions
Zero Correction ZC = ---------- mm

Sl.No.
Pitch Scale
Reading
PSR
3
10
?
? m
Head Scale
Coincidence
HSC
div
Observed reading
OR = PSR + (HSCXLC)
3
10
?
? m
Correct reading
CR = OR ? ZC
3
10
?
? m




Mean = ----------------
3
10
?
? m



9

PROCEDURE:
Torsional pendulum is suspended from vertical chuck. The length of the suspension wire is measured
between the vertical chuck and the chuck attached to the uniform circular disc (i). The circular disc is twisted
slightly without masses on the disc. Now it executes torsional oscillations. Care is taken to see that the disc
oscillates without wobbling. Time taken for 20 oscillations is noted with the help of a stop clock. Two trials are
taken. The average of these two trial readings is calculated from which the period of oscillations is found out
as T0.
Two identical cylindrical masses each of mass m are symmetrically placed on the disc on either side
of the wire at a distance d from the center of the disc. As before the disc is gently twisted. Time taken for 20
oscillations is noted from which the period of oscillation is calculated as T1.
The cylindrical masses are placed at a distance d2 from the center and the experiment is repeated.
The mean time period of oscillations is calculated T2.
The diameter of the specimen wire is measured accurately with the help of the screw gauge, at
various places on the wire. The average diameter and hence the radius of the wire is calculated as r.
Moment of inertia and the rigidity modulus are determined by the substituting the value of m, T 0, T1, T2,
T3, and l in the formula.










10

CALCULATION:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2

Mass of cylindrical mass, m = ----------- ? 10
-3
kg
Closest distance of the mass from the centre of the suspension wire, d1 = ------------ ? 10
-2
m
Farthest distance of the mass from the centre of suspension wire, d2= ------------? 10
-2
m
Period of oscillation without mass, To = ------------- s
Period of oscillation with mass at d1, T1= ------------ s
Period of oscillation with mass at d2, T2 = ------------- s

Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
= --------------- kg m
2
= --------------- kg m
2

Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
Moment of inertia, I = ------------------ kg m
2
Length of the wire, l = ------------------- ? 10
-2
m
Time of oscillation, To = ------------------ s
Radius of the wire, a = ------------------- ? 10
-3
m
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
= ----------------------
Rigidity modulus, n = ------------------- Nm
-2
11









RESULT:
(i)
The moment of inertia of the given circular disc, I = --------------- kg m
2
(ii)
The rigidity modulus of the material of the given wire, n = -------------- Nm
-2




1. State Hooke?s law.
2. Define ?Rigidity modulus
3. Define ?Moment of inertia
4. What is meant by torsional oscillation?
5. What is period of oscillation?
6. What is meant by twisting couple?
7. Define ? Shearing stress
8. Define ? Shearing strain
9. What is the unit of rigidity modulus?
10. What are the applications of torsional pendulum?


Viva ? voce
FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
2


PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science and fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems and use this knowledge to acquire
higher education.
2. Core competence
To train the students in Engineering Physics so as to apply their knowledge and training to compare,
and to analyze various engineering industrial problems for finding solutions.
3. Breadth
To provide relevant training and experience to bridge the gap between theoretical learning and
practice that enables them to find solutions for the real time problems in industry and to design products.
4. Professionalism
To inculcate professional and effective communication skills, leadership qualities and team spirit for
the students to make them multi-faceted personalities and develop their ability to relate engineering issues
to broader social context.
5. Lifelong learning/ethics
To demonstrate and practice ethical and professional responsibilities in the industry and society by
and large, through commitment and lifelong learning needed for successful professional career.





3


PROGRAMME OUTCOMES (POs)

a) To demonstrate and apply knowledge of Mathematics, Science and Engineering fundamentals in
Engineering physics
b) To determine the Moment of Inertia of given disc and Rigidity modulus of the given wire using
Torsional Pendulum
c) To determine Young?s modulus of a given bar using Non-Uniform bending
d) To utilize laser source and grating to estimate the wave length, particle size of given powder and
Numerical Aperture & acceptance angle of given optical fiber
e) To find the Thermal conductivity of a bad conductor using Lee?s Disc method
f) To Measure the velocity of ultrasonic wave in a liquid and compressibility of the liquid usingultrasonic
Interferometer
g) To determine the wavelength of Hg source using grating and spectrometer
h) To find the thickness of a thin wire using Air- wedge method
i) To participate and succeed in competitive exams and visualize and work on laboratory and
multidisciplinary tasks











4


BS 8161 ? PHYSICSLABORATORY
(Common to all branches of B.E. / B.TechProgrammes)
SYLLABUS


To introduce different experiments to test basic understanding of physics concepts applied in optics, thermal
physics, properties of matter and liquids.

LIST OF EXPERIMENTS: PHYSICS LABORATORY(Any 5 Experiments)
1. Determination of Rigidity modulus ? Torsion pendulum
2. Determination of Young? s modulus by Non uniform bending method
3. (a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
4. Determination of thermal conductivity of a bad conductor ? Lee?s Disc method.
5. Determination of velocity of sound and compressibility of liquid ? Ultrasonic interferometer
6. Determination of wavelength of mercury spectrum ? spectrometer grating
7. Determination of band gap of a semiconductor
8. Determination of thickness of a thin wire ? Air wedge method




Completion of the course, the students will be able to: apply physics principles of optics and thermal physics
to evaluate engineering properties of materials.


COURSE OUTCOMES
COURSE OBJECTIVES
5

BS 8161 ? PHYSICS LABORATORY
CONTENTS

Sl.No. Name of the Experiment (any 5 experiments)
Page
No.
1.
Determination of Rigidity modulus ? Torsion pendulum
6
2.
Determination of Young ?s modulus by Non uniform bending method
12
3.
(a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
18
4.
Determination of thermal conductivity of a bad conductor ? Lee ?s Disc method.
28
5.
Determination of velocity of sound and compressibility of liquid ? Ultrasonic
interferometer
37
6.
Determination of wavelength of mercury spectrum ? spectrometer grating
42
7.
Determination of thickness of a thin wire ? Air wedge method
48
MEASURING INSTRUMENTS
M1 Screw gauge 54
M2 Vernier Calipers 58
M3 Travelling Microscope 62
M4 Spectrometer 66








6

TORSIONAL PENDULUM










7

Expt. No.1 TORSIONAL PENDULUM

AIM:
To determine the moment of inertia of the given disc and hence to determine the rigidity modulus of
the material of the given suspension wire by torsional oscillations
APPARATUS REQUIRED:
Torsional pendulum, two equal masses, stop clock, screw gauge and meter scale

FORMULA:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
where
m ?mass of the cylinder placed on the disc (kg)
To ?period of the pendulum for a length of l without mass (s)
T1?period of the pendulum for the same length when mass m is placed at a distance d 1
from the center of the suspension wire (s)
T2?period of the pendulum for the same length when mass m is placed at a distance d 2
from the center of the suspension wire (s)
a ? radius of the suspension wire (m)




8

1. To determine the time period of the disc:
Length of the wire (l)= --------
2
10
?
? m
Position of the equal
masses
Time for 10 oscillations Time period
(one oscillation)
s
Trial-1
s
Trial-2
s
Mean
s
Without any masses T0
With masses at
d1 = x10
-2
m
T1
With masses at
d2 = x10
-2
m
T2

2. To determine the radius of the wire:
Least count =0 .01 mm. Zero Error ZE = --------- divisions
Zero Correction ZC = ---------- mm

Sl.No.
Pitch Scale
Reading
PSR
3
10
?
? m
Head Scale
Coincidence
HSC
div
Observed reading
OR = PSR + (HSCXLC)
3
10
?
? m
Correct reading
CR = OR ? ZC
3
10
?
? m




Mean = ----------------
3
10
?
? m



9

PROCEDURE:
Torsional pendulum is suspended from vertical chuck. The length of the suspension wire is measured
between the vertical chuck and the chuck attached to the uniform circular disc (i). The circular disc is twisted
slightly without masses on the disc. Now it executes torsional oscillations. Care is taken to see that the disc
oscillates without wobbling. Time taken for 20 oscillations is noted with the help of a stop clock. Two trials are
taken. The average of these two trial readings is calculated from which the period of oscillations is found out
as T0.
Two identical cylindrical masses each of mass m are symmetrically placed on the disc on either side
of the wire at a distance d from the center of the disc. As before the disc is gently twisted. Time taken for 20
oscillations is noted from which the period of oscillation is calculated as T1.
The cylindrical masses are placed at a distance d2 from the center and the experiment is repeated.
The mean time period of oscillations is calculated T2.
The diameter of the specimen wire is measured accurately with the help of the screw gauge, at
various places on the wire. The average diameter and hence the radius of the wire is calculated as r.
Moment of inertia and the rigidity modulus are determined by the substituting the value of m, T 0, T1, T2,
T3, and l in the formula.










10

CALCULATION:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2

Mass of cylindrical mass, m = ----------- ? 10
-3
kg
Closest distance of the mass from the centre of the suspension wire, d1 = ------------ ? 10
-2
m
Farthest distance of the mass from the centre of suspension wire, d2= ------------? 10
-2
m
Period of oscillation without mass, To = ------------- s
Period of oscillation with mass at d1, T1= ------------ s
Period of oscillation with mass at d2, T2 = ------------- s

Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
= --------------- kg m
2
= --------------- kg m
2

Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
Moment of inertia, I = ------------------ kg m
2
Length of the wire, l = ------------------- ? 10
-2
m
Time of oscillation, To = ------------------ s
Radius of the wire, a = ------------------- ? 10
-3
m
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
= ----------------------
Rigidity modulus, n = ------------------- Nm
-2
11









RESULT:
(i)
The moment of inertia of the given circular disc, I = --------------- kg m
2
(ii)
The rigidity modulus of the material of the given wire, n = -------------- Nm
-2




1. State Hooke?s law.
2. Define ?Rigidity modulus
3. Define ?Moment of inertia
4. What is meant by torsional oscillation?
5. What is period of oscillation?
6. What is meant by twisting couple?
7. Define ? Shearing stress
8. Define ? Shearing strain
9. What is the unit of rigidity modulus?
10. What are the applications of torsional pendulum?


Viva ? voce
12


Young?s Modulus ? Non Uniform Bending
To determine depression (y):
L.C =.001cm M = ___________
3
10
?
? kg

Sl.No

Load


3
10
?
?
k
g
Microscope reading
Mean

2
10
?
? m
Depression
y for M kg

2
10
?
? m
Loading Unloading
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
1 W
2 W+50
3 W+100
4 W+150
5 W+200
6 W+250

Mean (y) = ----------
2
10
?
? m





FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
2


PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science and fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems and use this knowledge to acquire
higher education.
2. Core competence
To train the students in Engineering Physics so as to apply their knowledge and training to compare,
and to analyze various engineering industrial problems for finding solutions.
3. Breadth
To provide relevant training and experience to bridge the gap between theoretical learning and
practice that enables them to find solutions for the real time problems in industry and to design products.
4. Professionalism
To inculcate professional and effective communication skills, leadership qualities and team spirit for
the students to make them multi-faceted personalities and develop their ability to relate engineering issues
to broader social context.
5. Lifelong learning/ethics
To demonstrate and practice ethical and professional responsibilities in the industry and society by
and large, through commitment and lifelong learning needed for successful professional career.





3


PROGRAMME OUTCOMES (POs)

a) To demonstrate and apply knowledge of Mathematics, Science and Engineering fundamentals in
Engineering physics
b) To determine the Moment of Inertia of given disc and Rigidity modulus of the given wire using
Torsional Pendulum
c) To determine Young?s modulus of a given bar using Non-Uniform bending
d) To utilize laser source and grating to estimate the wave length, particle size of given powder and
Numerical Aperture & acceptance angle of given optical fiber
e) To find the Thermal conductivity of a bad conductor using Lee?s Disc method
f) To Measure the velocity of ultrasonic wave in a liquid and compressibility of the liquid usingultrasonic
Interferometer
g) To determine the wavelength of Hg source using grating and spectrometer
h) To find the thickness of a thin wire using Air- wedge method
i) To participate and succeed in competitive exams and visualize and work on laboratory and
multidisciplinary tasks











4


BS 8161 ? PHYSICSLABORATORY
(Common to all branches of B.E. / B.TechProgrammes)
SYLLABUS


To introduce different experiments to test basic understanding of physics concepts applied in optics, thermal
physics, properties of matter and liquids.

LIST OF EXPERIMENTS: PHYSICS LABORATORY(Any 5 Experiments)
1. Determination of Rigidity modulus ? Torsion pendulum
2. Determination of Young? s modulus by Non uniform bending method
3. (a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
4. Determination of thermal conductivity of a bad conductor ? Lee?s Disc method.
5. Determination of velocity of sound and compressibility of liquid ? Ultrasonic interferometer
6. Determination of wavelength of mercury spectrum ? spectrometer grating
7. Determination of band gap of a semiconductor
8. Determination of thickness of a thin wire ? Air wedge method




Completion of the course, the students will be able to: apply physics principles of optics and thermal physics
to evaluate engineering properties of materials.


COURSE OUTCOMES
COURSE OBJECTIVES
5

BS 8161 ? PHYSICS LABORATORY
CONTENTS

Sl.No. Name of the Experiment (any 5 experiments)
Page
No.
1.
Determination of Rigidity modulus ? Torsion pendulum
6
2.
Determination of Young ?s modulus by Non uniform bending method
12
3.
(a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
18
4.
Determination of thermal conductivity of a bad conductor ? Lee ?s Disc method.
28
5.
Determination of velocity of sound and compressibility of liquid ? Ultrasonic
interferometer
37
6.
Determination of wavelength of mercury spectrum ? spectrometer grating
42
7.
Determination of thickness of a thin wire ? Air wedge method
48
MEASURING INSTRUMENTS
M1 Screw gauge 54
M2 Vernier Calipers 58
M3 Travelling Microscope 62
M4 Spectrometer 66








6

TORSIONAL PENDULUM










7

Expt. No.1 TORSIONAL PENDULUM

AIM:
To determine the moment of inertia of the given disc and hence to determine the rigidity modulus of
the material of the given suspension wire by torsional oscillations
APPARATUS REQUIRED:
Torsional pendulum, two equal masses, stop clock, screw gauge and meter scale

FORMULA:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
where
m ?mass of the cylinder placed on the disc (kg)
To ?period of the pendulum for a length of l without mass (s)
T1?period of the pendulum for the same length when mass m is placed at a distance d 1
from the center of the suspension wire (s)
T2?period of the pendulum for the same length when mass m is placed at a distance d 2
from the center of the suspension wire (s)
a ? radius of the suspension wire (m)




8

1. To determine the time period of the disc:
Length of the wire (l)= --------
2
10
?
? m
Position of the equal
masses
Time for 10 oscillations Time period
(one oscillation)
s
Trial-1
s
Trial-2
s
Mean
s
Without any masses T0
With masses at
d1 = x10
-2
m
T1
With masses at
d2 = x10
-2
m
T2

2. To determine the radius of the wire:
Least count =0 .01 mm. Zero Error ZE = --------- divisions
Zero Correction ZC = ---------- mm

Sl.No.
Pitch Scale
Reading
PSR
3
10
?
? m
Head Scale
Coincidence
HSC
div
Observed reading
OR = PSR + (HSCXLC)
3
10
?
? m
Correct reading
CR = OR ? ZC
3
10
?
? m




Mean = ----------------
3
10
?
? m



9

PROCEDURE:
Torsional pendulum is suspended from vertical chuck. The length of the suspension wire is measured
between the vertical chuck and the chuck attached to the uniform circular disc (i). The circular disc is twisted
slightly without masses on the disc. Now it executes torsional oscillations. Care is taken to see that the disc
oscillates without wobbling. Time taken for 20 oscillations is noted with the help of a stop clock. Two trials are
taken. The average of these two trial readings is calculated from which the period of oscillations is found out
as T0.
Two identical cylindrical masses each of mass m are symmetrically placed on the disc on either side
of the wire at a distance d from the center of the disc. As before the disc is gently twisted. Time taken for 20
oscillations is noted from which the period of oscillation is calculated as T1.
The cylindrical masses are placed at a distance d2 from the center and the experiment is repeated.
The mean time period of oscillations is calculated T2.
The diameter of the specimen wire is measured accurately with the help of the screw gauge, at
various places on the wire. The average diameter and hence the radius of the wire is calculated as r.
Moment of inertia and the rigidity modulus are determined by the substituting the value of m, T 0, T1, T2,
T3, and l in the formula.










10

CALCULATION:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2

Mass of cylindrical mass, m = ----------- ? 10
-3
kg
Closest distance of the mass from the centre of the suspension wire, d1 = ------------ ? 10
-2
m
Farthest distance of the mass from the centre of suspension wire, d2= ------------? 10
-2
m
Period of oscillation without mass, To = ------------- s
Period of oscillation with mass at d1, T1= ------------ s
Period of oscillation with mass at d2, T2 = ------------- s

Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
= --------------- kg m
2
= --------------- kg m
2

Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
Moment of inertia, I = ------------------ kg m
2
Length of the wire, l = ------------------- ? 10
-2
m
Time of oscillation, To = ------------------ s
Radius of the wire, a = ------------------- ? 10
-3
m
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
= ----------------------
Rigidity modulus, n = ------------------- Nm
-2
11









RESULT:
(i)
The moment of inertia of the given circular disc, I = --------------- kg m
2
(ii)
The rigidity modulus of the material of the given wire, n = -------------- Nm
-2




1. State Hooke?s law.
2. Define ?Rigidity modulus
3. Define ?Moment of inertia
4. What is meant by torsional oscillation?
5. What is period of oscillation?
6. What is meant by twisting couple?
7. Define ? Shearing stress
8. Define ? Shearing strain
9. What is the unit of rigidity modulus?
10. What are the applications of torsional pendulum?


Viva ? voce
12


Young?s Modulus ? Non Uniform Bending
To determine depression (y):
L.C =.001cm M = ___________
3
10
?
? kg

Sl.No

Load


3
10
?
?
k
g
Microscope reading
Mean

2
10
?
? m
Depression
y for M kg

2
10
?
? m
Loading Unloading
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
1 W
2 W+50
3 W+100
4 W+150
5 W+200
6 W+250

Mean (y) = ----------
2
10
?
? m





13

Expt. No.2 YOUNG?S MODULUS BY NON ? UNIFORM BENDING
AIM:
To determine the young?s modulus of the material of the given bar, by non-uniform bending method
APPARATUS REQUIRED:
Travelling microscope, wooden bar, knife- edge, weights hanger, slotted weight, vernier calipers,
screw gauge and pin
FORMULA:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Where,
g ? acceleration due to gravity (9.8 ms
-2
)
l ? length of the bar between two knife edges (m)
b ? breadth of the bar (m)
d ? thickness of the bar (m)
y ? depressiont in the scale reading due to the change of mass M (m)
PROCEDURE:
The given wooden bar, for which young?s modulus is to be determined, is paced symmetrically on the
two knife edges. The distance between the knife edges is measured as the length of the bar (l). It is adjusted
to be, say, 60 cm. the weight hanger is suspended at the centre of the bar. A pin is held vertically at the
centre of the bar with the help of wax.
The given bar is brought to elastic mood by loading and unloading the bar with slotted weights in steps
of 50 g. This is repeated for two or three times. With the hanger as dead load W, the microscope is focused on
to the tip of the pin. The tangential screw of the microscope is adjusted so that the image of the tip of the pin
just touches the horizontal cross wire of the eyepiece. The main scale reading and the vernier scale
coincidence corresponding to this position are noted.
FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
2


PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science and fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems and use this knowledge to acquire
higher education.
2. Core competence
To train the students in Engineering Physics so as to apply their knowledge and training to compare,
and to analyze various engineering industrial problems for finding solutions.
3. Breadth
To provide relevant training and experience to bridge the gap between theoretical learning and
practice that enables them to find solutions for the real time problems in industry and to design products.
4. Professionalism
To inculcate professional and effective communication skills, leadership qualities and team spirit for
the students to make them multi-faceted personalities and develop their ability to relate engineering issues
to broader social context.
5. Lifelong learning/ethics
To demonstrate and practice ethical and professional responsibilities in the industry and society by
and large, through commitment and lifelong learning needed for successful professional career.





3


PROGRAMME OUTCOMES (POs)

a) To demonstrate and apply knowledge of Mathematics, Science and Engineering fundamentals in
Engineering physics
b) To determine the Moment of Inertia of given disc and Rigidity modulus of the given wire using
Torsional Pendulum
c) To determine Young?s modulus of a given bar using Non-Uniform bending
d) To utilize laser source and grating to estimate the wave length, particle size of given powder and
Numerical Aperture & acceptance angle of given optical fiber
e) To find the Thermal conductivity of a bad conductor using Lee?s Disc method
f) To Measure the velocity of ultrasonic wave in a liquid and compressibility of the liquid usingultrasonic
Interferometer
g) To determine the wavelength of Hg source using grating and spectrometer
h) To find the thickness of a thin wire using Air- wedge method
i) To participate and succeed in competitive exams and visualize and work on laboratory and
multidisciplinary tasks











4


BS 8161 ? PHYSICSLABORATORY
(Common to all branches of B.E. / B.TechProgrammes)
SYLLABUS


To introduce different experiments to test basic understanding of physics concepts applied in optics, thermal
physics, properties of matter and liquids.

LIST OF EXPERIMENTS: PHYSICS LABORATORY(Any 5 Experiments)
1. Determination of Rigidity modulus ? Torsion pendulum
2. Determination of Young? s modulus by Non uniform bending method
3. (a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
4. Determination of thermal conductivity of a bad conductor ? Lee?s Disc method.
5. Determination of velocity of sound and compressibility of liquid ? Ultrasonic interferometer
6. Determination of wavelength of mercury spectrum ? spectrometer grating
7. Determination of band gap of a semiconductor
8. Determination of thickness of a thin wire ? Air wedge method




Completion of the course, the students will be able to: apply physics principles of optics and thermal physics
to evaluate engineering properties of materials.


COURSE OUTCOMES
COURSE OBJECTIVES
5

BS 8161 ? PHYSICS LABORATORY
CONTENTS

Sl.No. Name of the Experiment (any 5 experiments)
Page
No.
1.
Determination of Rigidity modulus ? Torsion pendulum
6
2.
Determination of Young ?s modulus by Non uniform bending method
12
3.
(a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
18
4.
Determination of thermal conductivity of a bad conductor ? Lee ?s Disc method.
28
5.
Determination of velocity of sound and compressibility of liquid ? Ultrasonic
interferometer
37
6.
Determination of wavelength of mercury spectrum ? spectrometer grating
42
7.
Determination of thickness of a thin wire ? Air wedge method
48
MEASURING INSTRUMENTS
M1 Screw gauge 54
M2 Vernier Calipers 58
M3 Travelling Microscope 62
M4 Spectrometer 66








6

TORSIONAL PENDULUM










7

Expt. No.1 TORSIONAL PENDULUM

AIM:
To determine the moment of inertia of the given disc and hence to determine the rigidity modulus of
the material of the given suspension wire by torsional oscillations
APPARATUS REQUIRED:
Torsional pendulum, two equal masses, stop clock, screw gauge and meter scale

FORMULA:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
where
m ?mass of the cylinder placed on the disc (kg)
To ?period of the pendulum for a length of l without mass (s)
T1?period of the pendulum for the same length when mass m is placed at a distance d 1
from the center of the suspension wire (s)
T2?period of the pendulum for the same length when mass m is placed at a distance d 2
from the center of the suspension wire (s)
a ? radius of the suspension wire (m)




8

1. To determine the time period of the disc:
Length of the wire (l)= --------
2
10
?
? m
Position of the equal
masses
Time for 10 oscillations Time period
(one oscillation)
s
Trial-1
s
Trial-2
s
Mean
s
Without any masses T0
With masses at
d1 = x10
-2
m
T1
With masses at
d2 = x10
-2
m
T2

2. To determine the radius of the wire:
Least count =0 .01 mm. Zero Error ZE = --------- divisions
Zero Correction ZC = ---------- mm

Sl.No.
Pitch Scale
Reading
PSR
3
10
?
? m
Head Scale
Coincidence
HSC
div
Observed reading
OR = PSR + (HSCXLC)
3
10
?
? m
Correct reading
CR = OR ? ZC
3
10
?
? m




Mean = ----------------
3
10
?
? m



9

PROCEDURE:
Torsional pendulum is suspended from vertical chuck. The length of the suspension wire is measured
between the vertical chuck and the chuck attached to the uniform circular disc (i). The circular disc is twisted
slightly without masses on the disc. Now it executes torsional oscillations. Care is taken to see that the disc
oscillates without wobbling. Time taken for 20 oscillations is noted with the help of a stop clock. Two trials are
taken. The average of these two trial readings is calculated from which the period of oscillations is found out
as T0.
Two identical cylindrical masses each of mass m are symmetrically placed on the disc on either side
of the wire at a distance d from the center of the disc. As before the disc is gently twisted. Time taken for 20
oscillations is noted from which the period of oscillation is calculated as T1.
The cylindrical masses are placed at a distance d2 from the center and the experiment is repeated.
The mean time period of oscillations is calculated T2.
The diameter of the specimen wire is measured accurately with the help of the screw gauge, at
various places on the wire. The average diameter and hence the radius of the wire is calculated as r.
Moment of inertia and the rigidity modulus are determined by the substituting the value of m, T 0, T1, T2,
T3, and l in the formula.










10

CALCULATION:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2

Mass of cylindrical mass, m = ----------- ? 10
-3
kg
Closest distance of the mass from the centre of the suspension wire, d1 = ------------ ? 10
-2
m
Farthest distance of the mass from the centre of suspension wire, d2= ------------? 10
-2
m
Period of oscillation without mass, To = ------------- s
Period of oscillation with mass at d1, T1= ------------ s
Period of oscillation with mass at d2, T2 = ------------- s

Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
= --------------- kg m
2
= --------------- kg m
2

Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
Moment of inertia, I = ------------------ kg m
2
Length of the wire, l = ------------------- ? 10
-2
m
Time of oscillation, To = ------------------ s
Radius of the wire, a = ------------------- ? 10
-3
m
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
= ----------------------
Rigidity modulus, n = ------------------- Nm
-2
11









RESULT:
(i)
The moment of inertia of the given circular disc, I = --------------- kg m
2
(ii)
The rigidity modulus of the material of the given wire, n = -------------- Nm
-2




1. State Hooke?s law.
2. Define ?Rigidity modulus
3. Define ?Moment of inertia
4. What is meant by torsional oscillation?
5. What is period of oscillation?
6. What is meant by twisting couple?
7. Define ? Shearing stress
8. Define ? Shearing strain
9. What is the unit of rigidity modulus?
10. What are the applications of torsional pendulum?


Viva ? voce
12


Young?s Modulus ? Non Uniform Bending
To determine depression (y):
L.C =.001cm M = ___________
3
10
?
? kg

Sl.No

Load


3
10
?
?
k
g
Microscope reading
Mean

2
10
?
? m
Depression
y for M kg

2
10
?
? m
Loading Unloading
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
1 W
2 W+50
3 W+100
4 W+150
5 W+200
6 W+250

Mean (y) = ----------
2
10
?
? m





13

Expt. No.2 YOUNG?S MODULUS BY NON ? UNIFORM BENDING
AIM:
To determine the young?s modulus of the material of the given bar, by non-uniform bending method
APPARATUS REQUIRED:
Travelling microscope, wooden bar, knife- edge, weights hanger, slotted weight, vernier calipers,
screw gauge and pin
FORMULA:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Where,
g ? acceleration due to gravity (9.8 ms
-2
)
l ? length of the bar between two knife edges (m)
b ? breadth of the bar (m)
d ? thickness of the bar (m)
y ? depressiont in the scale reading due to the change of mass M (m)
PROCEDURE:
The given wooden bar, for which young?s modulus is to be determined, is paced symmetrically on the
two knife edges. The distance between the knife edges is measured as the length of the bar (l). It is adjusted
to be, say, 60 cm. the weight hanger is suspended at the centre of the bar. A pin is held vertically at the
centre of the bar with the help of wax.
The given bar is brought to elastic mood by loading and unloading the bar with slotted weights in steps
of 50 g. This is repeated for two or three times. With the hanger as dead load W, the microscope is focused on
to the tip of the pin. The tangential screw of the microscope is adjusted so that the image of the tip of the pin
just touches the horizontal cross wire of the eyepiece. The main scale reading and the vernier scale
coincidence corresponding to this position are noted.
14

To find the breadth using vernier calipers, b:
Least count = ---------- cm Zero error = --------- div.
= ---------- ?10
-2
m Zero correction = ?ZE ?LC= --------- ?10
-2
m
Sl. No.

MSR
x 10
-2
m

VSC
div.
Observed reading
OR = MSR+(VSC ? LC)
x 10
-2
m
Correct Reading
CR = OR ? ZC
x 10
-2
m
1.

2.

3.


Mean, b = ------------------------?10
-2
m
To find the thickness using screw gauge, d:
Least count = ---------- mm Zero error = --------- div.
= ---------- ?10
-3
m Zero correction =ZE ?LC= --------- ?10
-3
m
Sl. No.

PSR
x 10
-3
m

HSC
div.
Observed reading
OR = PSR+ (HSC ? LC)
x 10
-3
m
Correct Reading
CR = OR ? ZC
x 10
-3
m
1.

2.

3.


Mean, d = ---------------------------?10
-3
m
FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
2


PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science and fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems and use this knowledge to acquire
higher education.
2. Core competence
To train the students in Engineering Physics so as to apply their knowledge and training to compare,
and to analyze various engineering industrial problems for finding solutions.
3. Breadth
To provide relevant training and experience to bridge the gap between theoretical learning and
practice that enables them to find solutions for the real time problems in industry and to design products.
4. Professionalism
To inculcate professional and effective communication skills, leadership qualities and team spirit for
the students to make them multi-faceted personalities and develop their ability to relate engineering issues
to broader social context.
5. Lifelong learning/ethics
To demonstrate and practice ethical and professional responsibilities in the industry and society by
and large, through commitment and lifelong learning needed for successful professional career.





3


PROGRAMME OUTCOMES (POs)

a) To demonstrate and apply knowledge of Mathematics, Science and Engineering fundamentals in
Engineering physics
b) To determine the Moment of Inertia of given disc and Rigidity modulus of the given wire using
Torsional Pendulum
c) To determine Young?s modulus of a given bar using Non-Uniform bending
d) To utilize laser source and grating to estimate the wave length, particle size of given powder and
Numerical Aperture & acceptance angle of given optical fiber
e) To find the Thermal conductivity of a bad conductor using Lee?s Disc method
f) To Measure the velocity of ultrasonic wave in a liquid and compressibility of the liquid usingultrasonic
Interferometer
g) To determine the wavelength of Hg source using grating and spectrometer
h) To find the thickness of a thin wire using Air- wedge method
i) To participate and succeed in competitive exams and visualize and work on laboratory and
multidisciplinary tasks











4


BS 8161 ? PHYSICSLABORATORY
(Common to all branches of B.E. / B.TechProgrammes)
SYLLABUS


To introduce different experiments to test basic understanding of physics concepts applied in optics, thermal
physics, properties of matter and liquids.

LIST OF EXPERIMENTS: PHYSICS LABORATORY(Any 5 Experiments)
1. Determination of Rigidity modulus ? Torsion pendulum
2. Determination of Young? s modulus by Non uniform bending method
3. (a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
4. Determination of thermal conductivity of a bad conductor ? Lee?s Disc method.
5. Determination of velocity of sound and compressibility of liquid ? Ultrasonic interferometer
6. Determination of wavelength of mercury spectrum ? spectrometer grating
7. Determination of band gap of a semiconductor
8. Determination of thickness of a thin wire ? Air wedge method




Completion of the course, the students will be able to: apply physics principles of optics and thermal physics
to evaluate engineering properties of materials.


COURSE OUTCOMES
COURSE OBJECTIVES
5

BS 8161 ? PHYSICS LABORATORY
CONTENTS

Sl.No. Name of the Experiment (any 5 experiments)
Page
No.
1.
Determination of Rigidity modulus ? Torsion pendulum
6
2.
Determination of Young ?s modulus by Non uniform bending method
12
3.
(a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
18
4.
Determination of thermal conductivity of a bad conductor ? Lee ?s Disc method.
28
5.
Determination of velocity of sound and compressibility of liquid ? Ultrasonic
interferometer
37
6.
Determination of wavelength of mercury spectrum ? spectrometer grating
42
7.
Determination of thickness of a thin wire ? Air wedge method
48
MEASURING INSTRUMENTS
M1 Screw gauge 54
M2 Vernier Calipers 58
M3 Travelling Microscope 62
M4 Spectrometer 66








6

TORSIONAL PENDULUM










7

Expt. No.1 TORSIONAL PENDULUM

AIM:
To determine the moment of inertia of the given disc and hence to determine the rigidity modulus of
the material of the given suspension wire by torsional oscillations
APPARATUS REQUIRED:
Torsional pendulum, two equal masses, stop clock, screw gauge and meter scale

FORMULA:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
where
m ?mass of the cylinder placed on the disc (kg)
To ?period of the pendulum for a length of l without mass (s)
T1?period of the pendulum for the same length when mass m is placed at a distance d 1
from the center of the suspension wire (s)
T2?period of the pendulum for the same length when mass m is placed at a distance d 2
from the center of the suspension wire (s)
a ? radius of the suspension wire (m)




8

1. To determine the time period of the disc:
Length of the wire (l)= --------
2
10
?
? m
Position of the equal
masses
Time for 10 oscillations Time period
(one oscillation)
s
Trial-1
s
Trial-2
s
Mean
s
Without any masses T0
With masses at
d1 = x10
-2
m
T1
With masses at
d2 = x10
-2
m
T2

2. To determine the radius of the wire:
Least count =0 .01 mm. Zero Error ZE = --------- divisions
Zero Correction ZC = ---------- mm

Sl.No.
Pitch Scale
Reading
PSR
3
10
?
? m
Head Scale
Coincidence
HSC
div
Observed reading
OR = PSR + (HSCXLC)
3
10
?
? m
Correct reading
CR = OR ? ZC
3
10
?
? m




Mean = ----------------
3
10
?
? m



9

PROCEDURE:
Torsional pendulum is suspended from vertical chuck. The length of the suspension wire is measured
between the vertical chuck and the chuck attached to the uniform circular disc (i). The circular disc is twisted
slightly without masses on the disc. Now it executes torsional oscillations. Care is taken to see that the disc
oscillates without wobbling. Time taken for 20 oscillations is noted with the help of a stop clock. Two trials are
taken. The average of these two trial readings is calculated from which the period of oscillations is found out
as T0.
Two identical cylindrical masses each of mass m are symmetrically placed on the disc on either side
of the wire at a distance d from the center of the disc. As before the disc is gently twisted. Time taken for 20
oscillations is noted from which the period of oscillation is calculated as T1.
The cylindrical masses are placed at a distance d2 from the center and the experiment is repeated.
The mean time period of oscillations is calculated T2.
The diameter of the specimen wire is measured accurately with the help of the screw gauge, at
various places on the wire. The average diameter and hence the radius of the wire is calculated as r.
Moment of inertia and the rigidity modulus are determined by the substituting the value of m, T 0, T1, T2,
T3, and l in the formula.










10

CALCULATION:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2

Mass of cylindrical mass, m = ----------- ? 10
-3
kg
Closest distance of the mass from the centre of the suspension wire, d1 = ------------ ? 10
-2
m
Farthest distance of the mass from the centre of suspension wire, d2= ------------? 10
-2
m
Period of oscillation without mass, To = ------------- s
Period of oscillation with mass at d1, T1= ------------ s
Period of oscillation with mass at d2, T2 = ------------- s

Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
= --------------- kg m
2
= --------------- kg m
2

Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
Moment of inertia, I = ------------------ kg m
2
Length of the wire, l = ------------------- ? 10
-2
m
Time of oscillation, To = ------------------ s
Radius of the wire, a = ------------------- ? 10
-3
m
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
= ----------------------
Rigidity modulus, n = ------------------- Nm
-2
11









RESULT:
(i)
The moment of inertia of the given circular disc, I = --------------- kg m
2
(ii)
The rigidity modulus of the material of the given wire, n = -------------- Nm
-2




1. State Hooke?s law.
2. Define ?Rigidity modulus
3. Define ?Moment of inertia
4. What is meant by torsional oscillation?
5. What is period of oscillation?
6. What is meant by twisting couple?
7. Define ? Shearing stress
8. Define ? Shearing strain
9. What is the unit of rigidity modulus?
10. What are the applications of torsional pendulum?


Viva ? voce
12


Young?s Modulus ? Non Uniform Bending
To determine depression (y):
L.C =.001cm M = ___________
3
10
?
? kg

Sl.No

Load


3
10
?
?
k
g
Microscope reading
Mean

2
10
?
? m
Depression
y for M kg

2
10
?
? m
Loading Unloading
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
1 W
2 W+50
3 W+100
4 W+150
5 W+200
6 W+250

Mean (y) = ----------
2
10
?
? m





13

Expt. No.2 YOUNG?S MODULUS BY NON ? UNIFORM BENDING
AIM:
To determine the young?s modulus of the material of the given bar, by non-uniform bending method
APPARATUS REQUIRED:
Travelling microscope, wooden bar, knife- edge, weights hanger, slotted weight, vernier calipers,
screw gauge and pin
FORMULA:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Where,
g ? acceleration due to gravity (9.8 ms
-2
)
l ? length of the bar between two knife edges (m)
b ? breadth of the bar (m)
d ? thickness of the bar (m)
y ? depressiont in the scale reading due to the change of mass M (m)
PROCEDURE:
The given wooden bar, for which young?s modulus is to be determined, is paced symmetrically on the
two knife edges. The distance between the knife edges is measured as the length of the bar (l). It is adjusted
to be, say, 60 cm. the weight hanger is suspended at the centre of the bar. A pin is held vertically at the
centre of the bar with the help of wax.
The given bar is brought to elastic mood by loading and unloading the bar with slotted weights in steps
of 50 g. This is repeated for two or three times. With the hanger as dead load W, the microscope is focused on
to the tip of the pin. The tangential screw of the microscope is adjusted so that the image of the tip of the pin
just touches the horizontal cross wire of the eyepiece. The main scale reading and the vernier scale
coincidence corresponding to this position are noted.
14

To find the breadth using vernier calipers, b:
Least count = ---------- cm Zero error = --------- div.
= ---------- ?10
-2
m Zero correction = ?ZE ?LC= --------- ?10
-2
m
Sl. No.

MSR
x 10
-2
m

VSC
div.
Observed reading
OR = MSR+(VSC ? LC)
x 10
-2
m
Correct Reading
CR = OR ? ZC
x 10
-2
m
1.

2.

3.


Mean, b = ------------------------?10
-2
m
To find the thickness using screw gauge, d:
Least count = ---------- mm Zero error = --------- div.
= ---------- ?10
-3
m Zero correction =ZE ?LC= --------- ?10
-3
m
Sl. No.

PSR
x 10
-3
m

HSC
div.
Observed reading
OR = PSR+ (HSC ? LC)
x 10
-3
m
Correct Reading
CR = OR ? ZC
x 10
-3
m
1.

2.

3.


Mean, d = ---------------------------?10
-3
m
15


The experiment is repeated by adding weights in steps of 50 g and every time the microscope is
adjusted for coincidence. The corresponding readings are noted. The experiment is repeated by unloading the
weights in steps of 50 g and the corresponding readings are tabulated. From this table, the shift in the scale
reading, say y, for a change of mass M is found out.
The breadth of the bar is measured at various points with the help of vernier calipers. Similarly the
thickness of the bar is measured by screw gauge. Substituting the values of M, y, l, d, b and g in the formula,
the young?s modulus of the material of the given bar is calculated.

















FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
2


PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science and fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems and use this knowledge to acquire
higher education.
2. Core competence
To train the students in Engineering Physics so as to apply their knowledge and training to compare,
and to analyze various engineering industrial problems for finding solutions.
3. Breadth
To provide relevant training and experience to bridge the gap between theoretical learning and
practice that enables them to find solutions for the real time problems in industry and to design products.
4. Professionalism
To inculcate professional and effective communication skills, leadership qualities and team spirit for
the students to make them multi-faceted personalities and develop their ability to relate engineering issues
to broader social context.
5. Lifelong learning/ethics
To demonstrate and practice ethical and professional responsibilities in the industry and society by
and large, through commitment and lifelong learning needed for successful professional career.





3


PROGRAMME OUTCOMES (POs)

a) To demonstrate and apply knowledge of Mathematics, Science and Engineering fundamentals in
Engineering physics
b) To determine the Moment of Inertia of given disc and Rigidity modulus of the given wire using
Torsional Pendulum
c) To determine Young?s modulus of a given bar using Non-Uniform bending
d) To utilize laser source and grating to estimate the wave length, particle size of given powder and
Numerical Aperture & acceptance angle of given optical fiber
e) To find the Thermal conductivity of a bad conductor using Lee?s Disc method
f) To Measure the velocity of ultrasonic wave in a liquid and compressibility of the liquid usingultrasonic
Interferometer
g) To determine the wavelength of Hg source using grating and spectrometer
h) To find the thickness of a thin wire using Air- wedge method
i) To participate and succeed in competitive exams and visualize and work on laboratory and
multidisciplinary tasks











4


BS 8161 ? PHYSICSLABORATORY
(Common to all branches of B.E. / B.TechProgrammes)
SYLLABUS


To introduce different experiments to test basic understanding of physics concepts applied in optics, thermal
physics, properties of matter and liquids.

LIST OF EXPERIMENTS: PHYSICS LABORATORY(Any 5 Experiments)
1. Determination of Rigidity modulus ? Torsion pendulum
2. Determination of Young? s modulus by Non uniform bending method
3. (a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
4. Determination of thermal conductivity of a bad conductor ? Lee?s Disc method.
5. Determination of velocity of sound and compressibility of liquid ? Ultrasonic interferometer
6. Determination of wavelength of mercury spectrum ? spectrometer grating
7. Determination of band gap of a semiconductor
8. Determination of thickness of a thin wire ? Air wedge method




Completion of the course, the students will be able to: apply physics principles of optics and thermal physics
to evaluate engineering properties of materials.


COURSE OUTCOMES
COURSE OBJECTIVES
5

BS 8161 ? PHYSICS LABORATORY
CONTENTS

Sl.No. Name of the Experiment (any 5 experiments)
Page
No.
1.
Determination of Rigidity modulus ? Torsion pendulum
6
2.
Determination of Young ?s modulus by Non uniform bending method
12
3.
(a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
18
4.
Determination of thermal conductivity of a bad conductor ? Lee ?s Disc method.
28
5.
Determination of velocity of sound and compressibility of liquid ? Ultrasonic
interferometer
37
6.
Determination of wavelength of mercury spectrum ? spectrometer grating
42
7.
Determination of thickness of a thin wire ? Air wedge method
48
MEASURING INSTRUMENTS
M1 Screw gauge 54
M2 Vernier Calipers 58
M3 Travelling Microscope 62
M4 Spectrometer 66








6

TORSIONAL PENDULUM










7

Expt. No.1 TORSIONAL PENDULUM

AIM:
To determine the moment of inertia of the given disc and hence to determine the rigidity modulus of
the material of the given suspension wire by torsional oscillations
APPARATUS REQUIRED:
Torsional pendulum, two equal masses, stop clock, screw gauge and meter scale

FORMULA:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
where
m ?mass of the cylinder placed on the disc (kg)
To ?period of the pendulum for a length of l without mass (s)
T1?period of the pendulum for the same length when mass m is placed at a distance d 1
from the center of the suspension wire (s)
T2?period of the pendulum for the same length when mass m is placed at a distance d 2
from the center of the suspension wire (s)
a ? radius of the suspension wire (m)




8

1. To determine the time period of the disc:
Length of the wire (l)= --------
2
10
?
? m
Position of the equal
masses
Time for 10 oscillations Time period
(one oscillation)
s
Trial-1
s
Trial-2
s
Mean
s
Without any masses T0
With masses at
d1 = x10
-2
m
T1
With masses at
d2 = x10
-2
m
T2

2. To determine the radius of the wire:
Least count =0 .01 mm. Zero Error ZE = --------- divisions
Zero Correction ZC = ---------- mm

Sl.No.
Pitch Scale
Reading
PSR
3
10
?
? m
Head Scale
Coincidence
HSC
div
Observed reading
OR = PSR + (HSCXLC)
3
10
?
? m
Correct reading
CR = OR ? ZC
3
10
?
? m




Mean = ----------------
3
10
?
? m



9

PROCEDURE:
Torsional pendulum is suspended from vertical chuck. The length of the suspension wire is measured
between the vertical chuck and the chuck attached to the uniform circular disc (i). The circular disc is twisted
slightly without masses on the disc. Now it executes torsional oscillations. Care is taken to see that the disc
oscillates without wobbling. Time taken for 20 oscillations is noted with the help of a stop clock. Two trials are
taken. The average of these two trial readings is calculated from which the period of oscillations is found out
as T0.
Two identical cylindrical masses each of mass m are symmetrically placed on the disc on either side
of the wire at a distance d from the center of the disc. As before the disc is gently twisted. Time taken for 20
oscillations is noted from which the period of oscillation is calculated as T1.
The cylindrical masses are placed at a distance d2 from the center and the experiment is repeated.
The mean time period of oscillations is calculated T2.
The diameter of the specimen wire is measured accurately with the help of the screw gauge, at
various places on the wire. The average diameter and hence the radius of the wire is calculated as r.
Moment of inertia and the rigidity modulus are determined by the substituting the value of m, T 0, T1, T2,
T3, and l in the formula.










10

CALCULATION:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2

Mass of cylindrical mass, m = ----------- ? 10
-3
kg
Closest distance of the mass from the centre of the suspension wire, d1 = ------------ ? 10
-2
m
Farthest distance of the mass from the centre of suspension wire, d2= ------------? 10
-2
m
Period of oscillation without mass, To = ------------- s
Period of oscillation with mass at d1, T1= ------------ s
Period of oscillation with mass at d2, T2 = ------------- s

Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
= --------------- kg m
2
= --------------- kg m
2

Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
Moment of inertia, I = ------------------ kg m
2
Length of the wire, l = ------------------- ? 10
-2
m
Time of oscillation, To = ------------------ s
Radius of the wire, a = ------------------- ? 10
-3
m
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
= ----------------------
Rigidity modulus, n = ------------------- Nm
-2
11









RESULT:
(i)
The moment of inertia of the given circular disc, I = --------------- kg m
2
(ii)
The rigidity modulus of the material of the given wire, n = -------------- Nm
-2




1. State Hooke?s law.
2. Define ?Rigidity modulus
3. Define ?Moment of inertia
4. What is meant by torsional oscillation?
5. What is period of oscillation?
6. What is meant by twisting couple?
7. Define ? Shearing stress
8. Define ? Shearing strain
9. What is the unit of rigidity modulus?
10. What are the applications of torsional pendulum?


Viva ? voce
12


Young?s Modulus ? Non Uniform Bending
To determine depression (y):
L.C =.001cm M = ___________
3
10
?
? kg

Sl.No

Load


3
10
?
?
k
g
Microscope reading
Mean

2
10
?
? m
Depression
y for M kg

2
10
?
? m
Loading Unloading
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
1 W
2 W+50
3 W+100
4 W+150
5 W+200
6 W+250

Mean (y) = ----------
2
10
?
? m





13

Expt. No.2 YOUNG?S MODULUS BY NON ? UNIFORM BENDING
AIM:
To determine the young?s modulus of the material of the given bar, by non-uniform bending method
APPARATUS REQUIRED:
Travelling microscope, wooden bar, knife- edge, weights hanger, slotted weight, vernier calipers,
screw gauge and pin
FORMULA:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Where,
g ? acceleration due to gravity (9.8 ms
-2
)
l ? length of the bar between two knife edges (m)
b ? breadth of the bar (m)
d ? thickness of the bar (m)
y ? depressiont in the scale reading due to the change of mass M (m)
PROCEDURE:
The given wooden bar, for which young?s modulus is to be determined, is paced symmetrically on the
two knife edges. The distance between the knife edges is measured as the length of the bar (l). It is adjusted
to be, say, 60 cm. the weight hanger is suspended at the centre of the bar. A pin is held vertically at the
centre of the bar with the help of wax.
The given bar is brought to elastic mood by loading and unloading the bar with slotted weights in steps
of 50 g. This is repeated for two or three times. With the hanger as dead load W, the microscope is focused on
to the tip of the pin. The tangential screw of the microscope is adjusted so that the image of the tip of the pin
just touches the horizontal cross wire of the eyepiece. The main scale reading and the vernier scale
coincidence corresponding to this position are noted.
14

To find the breadth using vernier calipers, b:
Least count = ---------- cm Zero error = --------- div.
= ---------- ?10
-2
m Zero correction = ?ZE ?LC= --------- ?10
-2
m
Sl. No.

MSR
x 10
-2
m

VSC
div.
Observed reading
OR = MSR+(VSC ? LC)
x 10
-2
m
Correct Reading
CR = OR ? ZC
x 10
-2
m
1.

2.

3.


Mean, b = ------------------------?10
-2
m
To find the thickness using screw gauge, d:
Least count = ---------- mm Zero error = --------- div.
= ---------- ?10
-3
m Zero correction =ZE ?LC= --------- ?10
-3
m
Sl. No.

PSR
x 10
-3
m

HSC
div.
Observed reading
OR = PSR+ (HSC ? LC)
x 10
-3
m
Correct Reading
CR = OR ? ZC
x 10
-3
m
1.

2.

3.


Mean, d = ---------------------------?10
-3
m
15


The experiment is repeated by adding weights in steps of 50 g and every time the microscope is
adjusted for coincidence. The corresponding readings are noted. The experiment is repeated by unloading the
weights in steps of 50 g and the corresponding readings are tabulated. From this table, the shift in the scale
reading, say y, for a change of mass M is found out.
The breadth of the bar is measured at various points with the help of vernier calipers. Similarly the
thickness of the bar is measured by screw gauge. Substituting the values of M, y, l, d, b and g in the formula,
the young?s modulus of the material of the given bar is calculated.

















16

CALCULATION:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Acceleration due to gravity, g = 9.8 ms
-2
Length of the bar between two knife edges, l = ------------ ?10
-2
m
Breadth of the bar, b = ----------- ?10
-2
m
Thickness of the bar, d = ----------- ?10
-3
m
y = -----------?10
-2
m
E =
???? ?? 2
4?? ?? 3
?? Nm
-2

= ---------------
Young?s modulus, E = ----------- Nm
-2












FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
2


PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science and fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems and use this knowledge to acquire
higher education.
2. Core competence
To train the students in Engineering Physics so as to apply their knowledge and training to compare,
and to analyze various engineering industrial problems for finding solutions.
3. Breadth
To provide relevant training and experience to bridge the gap between theoretical learning and
practice that enables them to find solutions for the real time problems in industry and to design products.
4. Professionalism
To inculcate professional and effective communication skills, leadership qualities and team spirit for
the students to make them multi-faceted personalities and develop their ability to relate engineering issues
to broader social context.
5. Lifelong learning/ethics
To demonstrate and practice ethical and professional responsibilities in the industry and society by
and large, through commitment and lifelong learning needed for successful professional career.





3


PROGRAMME OUTCOMES (POs)

a) To demonstrate and apply knowledge of Mathematics, Science and Engineering fundamentals in
Engineering physics
b) To determine the Moment of Inertia of given disc and Rigidity modulus of the given wire using
Torsional Pendulum
c) To determine Young?s modulus of a given bar using Non-Uniform bending
d) To utilize laser source and grating to estimate the wave length, particle size of given powder and
Numerical Aperture & acceptance angle of given optical fiber
e) To find the Thermal conductivity of a bad conductor using Lee?s Disc method
f) To Measure the velocity of ultrasonic wave in a liquid and compressibility of the liquid usingultrasonic
Interferometer
g) To determine the wavelength of Hg source using grating and spectrometer
h) To find the thickness of a thin wire using Air- wedge method
i) To participate and succeed in competitive exams and visualize and work on laboratory and
multidisciplinary tasks











4


BS 8161 ? PHYSICSLABORATORY
(Common to all branches of B.E. / B.TechProgrammes)
SYLLABUS


To introduce different experiments to test basic understanding of physics concepts applied in optics, thermal
physics, properties of matter and liquids.

LIST OF EXPERIMENTS: PHYSICS LABORATORY(Any 5 Experiments)
1. Determination of Rigidity modulus ? Torsion pendulum
2. Determination of Young? s modulus by Non uniform bending method
3. (a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
4. Determination of thermal conductivity of a bad conductor ? Lee?s Disc method.
5. Determination of velocity of sound and compressibility of liquid ? Ultrasonic interferometer
6. Determination of wavelength of mercury spectrum ? spectrometer grating
7. Determination of band gap of a semiconductor
8. Determination of thickness of a thin wire ? Air wedge method




Completion of the course, the students will be able to: apply physics principles of optics and thermal physics
to evaluate engineering properties of materials.


COURSE OUTCOMES
COURSE OBJECTIVES
5

BS 8161 ? PHYSICS LABORATORY
CONTENTS

Sl.No. Name of the Experiment (any 5 experiments)
Page
No.
1.
Determination of Rigidity modulus ? Torsion pendulum
6
2.
Determination of Young ?s modulus by Non uniform bending method
12
3.
(a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
18
4.
Determination of thermal conductivity of a bad conductor ? Lee ?s Disc method.
28
5.
Determination of velocity of sound and compressibility of liquid ? Ultrasonic
interferometer
37
6.
Determination of wavelength of mercury spectrum ? spectrometer grating
42
7.
Determination of thickness of a thin wire ? Air wedge method
48
MEASURING INSTRUMENTS
M1 Screw gauge 54
M2 Vernier Calipers 58
M3 Travelling Microscope 62
M4 Spectrometer 66








6

TORSIONAL PENDULUM










7

Expt. No.1 TORSIONAL PENDULUM

AIM:
To determine the moment of inertia of the given disc and hence to determine the rigidity modulus of
the material of the given suspension wire by torsional oscillations
APPARATUS REQUIRED:
Torsional pendulum, two equal masses, stop clock, screw gauge and meter scale

FORMULA:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
where
m ?mass of the cylinder placed on the disc (kg)
To ?period of the pendulum for a length of l without mass (s)
T1?period of the pendulum for the same length when mass m is placed at a distance d 1
from the center of the suspension wire (s)
T2?period of the pendulum for the same length when mass m is placed at a distance d 2
from the center of the suspension wire (s)
a ? radius of the suspension wire (m)




8

1. To determine the time period of the disc:
Length of the wire (l)= --------
2
10
?
? m
Position of the equal
masses
Time for 10 oscillations Time period
(one oscillation)
s
Trial-1
s
Trial-2
s
Mean
s
Without any masses T0
With masses at
d1 = x10
-2
m
T1
With masses at
d2 = x10
-2
m
T2

2. To determine the radius of the wire:
Least count =0 .01 mm. Zero Error ZE = --------- divisions
Zero Correction ZC = ---------- mm

Sl.No.
Pitch Scale
Reading
PSR
3
10
?
? m
Head Scale
Coincidence
HSC
div
Observed reading
OR = PSR + (HSCXLC)
3
10
?
? m
Correct reading
CR = OR ? ZC
3
10
?
? m




Mean = ----------------
3
10
?
? m



9

PROCEDURE:
Torsional pendulum is suspended from vertical chuck. The length of the suspension wire is measured
between the vertical chuck and the chuck attached to the uniform circular disc (i). The circular disc is twisted
slightly without masses on the disc. Now it executes torsional oscillations. Care is taken to see that the disc
oscillates without wobbling. Time taken for 20 oscillations is noted with the help of a stop clock. Two trials are
taken. The average of these two trial readings is calculated from which the period of oscillations is found out
as T0.
Two identical cylindrical masses each of mass m are symmetrically placed on the disc on either side
of the wire at a distance d from the center of the disc. As before the disc is gently twisted. Time taken for 20
oscillations is noted from which the period of oscillation is calculated as T1.
The cylindrical masses are placed at a distance d2 from the center and the experiment is repeated.
The mean time period of oscillations is calculated T2.
The diameter of the specimen wire is measured accurately with the help of the screw gauge, at
various places on the wire. The average diameter and hence the radius of the wire is calculated as r.
Moment of inertia and the rigidity modulus are determined by the substituting the value of m, T 0, T1, T2,
T3, and l in the formula.










10

CALCULATION:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2

Mass of cylindrical mass, m = ----------- ? 10
-3
kg
Closest distance of the mass from the centre of the suspension wire, d1 = ------------ ? 10
-2
m
Farthest distance of the mass from the centre of suspension wire, d2= ------------? 10
-2
m
Period of oscillation without mass, To = ------------- s
Period of oscillation with mass at d1, T1= ------------ s
Period of oscillation with mass at d2, T2 = ------------- s

Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
= --------------- kg m
2
= --------------- kg m
2

Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
Moment of inertia, I = ------------------ kg m
2
Length of the wire, l = ------------------- ? 10
-2
m
Time of oscillation, To = ------------------ s
Radius of the wire, a = ------------------- ? 10
-3
m
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
= ----------------------
Rigidity modulus, n = ------------------- Nm
-2
11









RESULT:
(i)
The moment of inertia of the given circular disc, I = --------------- kg m
2
(ii)
The rigidity modulus of the material of the given wire, n = -------------- Nm
-2




1. State Hooke?s law.
2. Define ?Rigidity modulus
3. Define ?Moment of inertia
4. What is meant by torsional oscillation?
5. What is period of oscillation?
6. What is meant by twisting couple?
7. Define ? Shearing stress
8. Define ? Shearing strain
9. What is the unit of rigidity modulus?
10. What are the applications of torsional pendulum?


Viva ? voce
12


Young?s Modulus ? Non Uniform Bending
To determine depression (y):
L.C =.001cm M = ___________
3
10
?
? kg

Sl.No

Load


3
10
?
?
k
g
Microscope reading
Mean

2
10
?
? m
Depression
y for M kg

2
10
?
? m
Loading Unloading
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
1 W
2 W+50
3 W+100
4 W+150
5 W+200
6 W+250

Mean (y) = ----------
2
10
?
? m





13

Expt. No.2 YOUNG?S MODULUS BY NON ? UNIFORM BENDING
AIM:
To determine the young?s modulus of the material of the given bar, by non-uniform bending method
APPARATUS REQUIRED:
Travelling microscope, wooden bar, knife- edge, weights hanger, slotted weight, vernier calipers,
screw gauge and pin
FORMULA:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Where,
g ? acceleration due to gravity (9.8 ms
-2
)
l ? length of the bar between two knife edges (m)
b ? breadth of the bar (m)
d ? thickness of the bar (m)
y ? depressiont in the scale reading due to the change of mass M (m)
PROCEDURE:
The given wooden bar, for which young?s modulus is to be determined, is paced symmetrically on the
two knife edges. The distance between the knife edges is measured as the length of the bar (l). It is adjusted
to be, say, 60 cm. the weight hanger is suspended at the centre of the bar. A pin is held vertically at the
centre of the bar with the help of wax.
The given bar is brought to elastic mood by loading and unloading the bar with slotted weights in steps
of 50 g. This is repeated for two or three times. With the hanger as dead load W, the microscope is focused on
to the tip of the pin. The tangential screw of the microscope is adjusted so that the image of the tip of the pin
just touches the horizontal cross wire of the eyepiece. The main scale reading and the vernier scale
coincidence corresponding to this position are noted.
14

To find the breadth using vernier calipers, b:
Least count = ---------- cm Zero error = --------- div.
= ---------- ?10
-2
m Zero correction = ?ZE ?LC= --------- ?10
-2
m
Sl. No.

MSR
x 10
-2
m

VSC
div.
Observed reading
OR = MSR+(VSC ? LC)
x 10
-2
m
Correct Reading
CR = OR ? ZC
x 10
-2
m
1.

2.

3.


Mean, b = ------------------------?10
-2
m
To find the thickness using screw gauge, d:
Least count = ---------- mm Zero error = --------- div.
= ---------- ?10
-3
m Zero correction =ZE ?LC= --------- ?10
-3
m
Sl. No.

PSR
x 10
-3
m

HSC
div.
Observed reading
OR = PSR+ (HSC ? LC)
x 10
-3
m
Correct Reading
CR = OR ? ZC
x 10
-3
m
1.

2.

3.


Mean, d = ---------------------------?10
-3
m
15


The experiment is repeated by adding weights in steps of 50 g and every time the microscope is
adjusted for coincidence. The corresponding readings are noted. The experiment is repeated by unloading the
weights in steps of 50 g and the corresponding readings are tabulated. From this table, the shift in the scale
reading, say y, for a change of mass M is found out.
The breadth of the bar is measured at various points with the help of vernier calipers. Similarly the
thickness of the bar is measured by screw gauge. Substituting the values of M, y, l, d, b and g in the formula,
the young?s modulus of the material of the given bar is calculated.

















16

CALCULATION:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Acceleration due to gravity, g = 9.8 ms
-2
Length of the bar between two knife edges, l = ------------ ?10
-2
m
Breadth of the bar, b = ----------- ?10
-2
m
Thickness of the bar, d = ----------- ?10
-3
m
y = -----------?10
-2
m
E =
???? ?? 2
4?? ?? 3
?? Nm
-2

= ---------------
Young?s modulus, E = ----------- Nm
-2












17








RESULT:
Young?s modulus of the material of the given bar, E = ---------- Nm
-2


1. Define ? Young?s modulus
2. What is meant by Non-uniform bending?
3. Define ? Stress and strain
4. State Hooke?s law.
5. Define ? Neutral axis
6. What is the SI unit of young?s modulus?
7. Define ? Elastic limit
8. Define ? Elasticity
9. What are the factors affecting elasticity?
10. Define ? Elastic fatigue

Viva ? voce
FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
2


PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science and fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems and use this knowledge to acquire
higher education.
2. Core competence
To train the students in Engineering Physics so as to apply their knowledge and training to compare,
and to analyze various engineering industrial problems for finding solutions.
3. Breadth
To provide relevant training and experience to bridge the gap between theoretical learning and
practice that enables them to find solutions for the real time problems in industry and to design products.
4. Professionalism
To inculcate professional and effective communication skills, leadership qualities and team spirit for
the students to make them multi-faceted personalities and develop their ability to relate engineering issues
to broader social context.
5. Lifelong learning/ethics
To demonstrate and practice ethical and professional responsibilities in the industry and society by
and large, through commitment and lifelong learning needed for successful professional career.





3


PROGRAMME OUTCOMES (POs)

a) To demonstrate and apply knowledge of Mathematics, Science and Engineering fundamentals in
Engineering physics
b) To determine the Moment of Inertia of given disc and Rigidity modulus of the given wire using
Torsional Pendulum
c) To determine Young?s modulus of a given bar using Non-Uniform bending
d) To utilize laser source and grating to estimate the wave length, particle size of given powder and
Numerical Aperture & acceptance angle of given optical fiber
e) To find the Thermal conductivity of a bad conductor using Lee?s Disc method
f) To Measure the velocity of ultrasonic wave in a liquid and compressibility of the liquid usingultrasonic
Interferometer
g) To determine the wavelength of Hg source using grating and spectrometer
h) To find the thickness of a thin wire using Air- wedge method
i) To participate and succeed in competitive exams and visualize and work on laboratory and
multidisciplinary tasks











4


BS 8161 ? PHYSICSLABORATORY
(Common to all branches of B.E. / B.TechProgrammes)
SYLLABUS


To introduce different experiments to test basic understanding of physics concepts applied in optics, thermal
physics, properties of matter and liquids.

LIST OF EXPERIMENTS: PHYSICS LABORATORY(Any 5 Experiments)
1. Determination of Rigidity modulus ? Torsion pendulum
2. Determination of Young? s modulus by Non uniform bending method
3. (a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
4. Determination of thermal conductivity of a bad conductor ? Lee?s Disc method.
5. Determination of velocity of sound and compressibility of liquid ? Ultrasonic interferometer
6. Determination of wavelength of mercury spectrum ? spectrometer grating
7. Determination of band gap of a semiconductor
8. Determination of thickness of a thin wire ? Air wedge method




Completion of the course, the students will be able to: apply physics principles of optics and thermal physics
to evaluate engineering properties of materials.


COURSE OUTCOMES
COURSE OBJECTIVES
5

BS 8161 ? PHYSICS LABORATORY
CONTENTS

Sl.No. Name of the Experiment (any 5 experiments)
Page
No.
1.
Determination of Rigidity modulus ? Torsion pendulum
6
2.
Determination of Young ?s modulus by Non uniform bending method
12
3.
(a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
18
4.
Determination of thermal conductivity of a bad conductor ? Lee ?s Disc method.
28
5.
Determination of velocity of sound and compressibility of liquid ? Ultrasonic
interferometer
37
6.
Determination of wavelength of mercury spectrum ? spectrometer grating
42
7.
Determination of thickness of a thin wire ? Air wedge method
48
MEASURING INSTRUMENTS
M1 Screw gauge 54
M2 Vernier Calipers 58
M3 Travelling Microscope 62
M4 Spectrometer 66








6

TORSIONAL PENDULUM










7

Expt. No.1 TORSIONAL PENDULUM

AIM:
To determine the moment of inertia of the given disc and hence to determine the rigidity modulus of
the material of the given suspension wire by torsional oscillations
APPARATUS REQUIRED:
Torsional pendulum, two equal masses, stop clock, screw gauge and meter scale

FORMULA:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
where
m ?mass of the cylinder placed on the disc (kg)
To ?period of the pendulum for a length of l without mass (s)
T1?period of the pendulum for the same length when mass m is placed at a distance d 1
from the center of the suspension wire (s)
T2?period of the pendulum for the same length when mass m is placed at a distance d 2
from the center of the suspension wire (s)
a ? radius of the suspension wire (m)




8

1. To determine the time period of the disc:
Length of the wire (l)= --------
2
10
?
? m
Position of the equal
masses
Time for 10 oscillations Time period
(one oscillation)
s
Trial-1
s
Trial-2
s
Mean
s
Without any masses T0
With masses at
d1 = x10
-2
m
T1
With masses at
d2 = x10
-2
m
T2

2. To determine the radius of the wire:
Least count =0 .01 mm. Zero Error ZE = --------- divisions
Zero Correction ZC = ---------- mm

Sl.No.
Pitch Scale
Reading
PSR
3
10
?
? m
Head Scale
Coincidence
HSC
div
Observed reading
OR = PSR + (HSCXLC)
3
10
?
? m
Correct reading
CR = OR ? ZC
3
10
?
? m




Mean = ----------------
3
10
?
? m



9

PROCEDURE:
Torsional pendulum is suspended from vertical chuck. The length of the suspension wire is measured
between the vertical chuck and the chuck attached to the uniform circular disc (i). The circular disc is twisted
slightly without masses on the disc. Now it executes torsional oscillations. Care is taken to see that the disc
oscillates without wobbling. Time taken for 20 oscillations is noted with the help of a stop clock. Two trials are
taken. The average of these two trial readings is calculated from which the period of oscillations is found out
as T0.
Two identical cylindrical masses each of mass m are symmetrically placed on the disc on either side
of the wire at a distance d from the center of the disc. As before the disc is gently twisted. Time taken for 20
oscillations is noted from which the period of oscillation is calculated as T1.
The cylindrical masses are placed at a distance d2 from the center and the experiment is repeated.
The mean time period of oscillations is calculated T2.
The diameter of the specimen wire is measured accurately with the help of the screw gauge, at
various places on the wire. The average diameter and hence the radius of the wire is calculated as r.
Moment of inertia and the rigidity modulus are determined by the substituting the value of m, T 0, T1, T2,
T3, and l in the formula.










10

CALCULATION:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2

Mass of cylindrical mass, m = ----------- ? 10
-3
kg
Closest distance of the mass from the centre of the suspension wire, d1 = ------------ ? 10
-2
m
Farthest distance of the mass from the centre of suspension wire, d2= ------------? 10
-2
m
Period of oscillation without mass, To = ------------- s
Period of oscillation with mass at d1, T1= ------------ s
Period of oscillation with mass at d2, T2 = ------------- s

Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
= --------------- kg m
2
= --------------- kg m
2

Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
Moment of inertia, I = ------------------ kg m
2
Length of the wire, l = ------------------- ? 10
-2
m
Time of oscillation, To = ------------------ s
Radius of the wire, a = ------------------- ? 10
-3
m
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
= ----------------------
Rigidity modulus, n = ------------------- Nm
-2
11









RESULT:
(i)
The moment of inertia of the given circular disc, I = --------------- kg m
2
(ii)
The rigidity modulus of the material of the given wire, n = -------------- Nm
-2




1. State Hooke?s law.
2. Define ?Rigidity modulus
3. Define ?Moment of inertia
4. What is meant by torsional oscillation?
5. What is period of oscillation?
6. What is meant by twisting couple?
7. Define ? Shearing stress
8. Define ? Shearing strain
9. What is the unit of rigidity modulus?
10. What are the applications of torsional pendulum?


Viva ? voce
12


Young?s Modulus ? Non Uniform Bending
To determine depression (y):
L.C =.001cm M = ___________
3
10
?
? kg

Sl.No

Load


3
10
?
?
k
g
Microscope reading
Mean

2
10
?
? m
Depression
y for M kg

2
10
?
? m
Loading Unloading
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
1 W
2 W+50
3 W+100
4 W+150
5 W+200
6 W+250

Mean (y) = ----------
2
10
?
? m





13

Expt. No.2 YOUNG?S MODULUS BY NON ? UNIFORM BENDING
AIM:
To determine the young?s modulus of the material of the given bar, by non-uniform bending method
APPARATUS REQUIRED:
Travelling microscope, wooden bar, knife- edge, weights hanger, slotted weight, vernier calipers,
screw gauge and pin
FORMULA:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Where,
g ? acceleration due to gravity (9.8 ms
-2
)
l ? length of the bar between two knife edges (m)
b ? breadth of the bar (m)
d ? thickness of the bar (m)
y ? depressiont in the scale reading due to the change of mass M (m)
PROCEDURE:
The given wooden bar, for which young?s modulus is to be determined, is paced symmetrically on the
two knife edges. The distance between the knife edges is measured as the length of the bar (l). It is adjusted
to be, say, 60 cm. the weight hanger is suspended at the centre of the bar. A pin is held vertically at the
centre of the bar with the help of wax.
The given bar is brought to elastic mood by loading and unloading the bar with slotted weights in steps
of 50 g. This is repeated for two or three times. With the hanger as dead load W, the microscope is focused on
to the tip of the pin. The tangential screw of the microscope is adjusted so that the image of the tip of the pin
just touches the horizontal cross wire of the eyepiece. The main scale reading and the vernier scale
coincidence corresponding to this position are noted.
14

To find the breadth using vernier calipers, b:
Least count = ---------- cm Zero error = --------- div.
= ---------- ?10
-2
m Zero correction = ?ZE ?LC= --------- ?10
-2
m
Sl. No.

MSR
x 10
-2
m

VSC
div.
Observed reading
OR = MSR+(VSC ? LC)
x 10
-2
m
Correct Reading
CR = OR ? ZC
x 10
-2
m
1.

2.

3.


Mean, b = ------------------------?10
-2
m
To find the thickness using screw gauge, d:
Least count = ---------- mm Zero error = --------- div.
= ---------- ?10
-3
m Zero correction =ZE ?LC= --------- ?10
-3
m
Sl. No.

PSR
x 10
-3
m

HSC
div.
Observed reading
OR = PSR+ (HSC ? LC)
x 10
-3
m
Correct Reading
CR = OR ? ZC
x 10
-3
m
1.

2.

3.


Mean, d = ---------------------------?10
-3
m
15


The experiment is repeated by adding weights in steps of 50 g and every time the microscope is
adjusted for coincidence. The corresponding readings are noted. The experiment is repeated by unloading the
weights in steps of 50 g and the corresponding readings are tabulated. From this table, the shift in the scale
reading, say y, for a change of mass M is found out.
The breadth of the bar is measured at various points with the help of vernier calipers. Similarly the
thickness of the bar is measured by screw gauge. Substituting the values of M, y, l, d, b and g in the formula,
the young?s modulus of the material of the given bar is calculated.

















16

CALCULATION:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Acceleration due to gravity, g = 9.8 ms
-2
Length of the bar between two knife edges, l = ------------ ?10
-2
m
Breadth of the bar, b = ----------- ?10
-2
m
Thickness of the bar, d = ----------- ?10
-3
m
y = -----------?10
-2
m
E =
???? ?? 2
4?? ?? 3
?? Nm
-2

= ---------------
Young?s modulus, E = ----------- Nm
-2












17








RESULT:
Young?s modulus of the material of the given bar, E = ---------- Nm
-2


1. Define ? Young?s modulus
2. What is meant by Non-uniform bending?
3. Define ? Stress and strain
4. State Hooke?s law.
5. Define ? Neutral axis
6. What is the SI unit of young?s modulus?
7. Define ? Elastic limit
8. Define ? Elasticity
9. What are the factors affecting elasticity?
10. Define ? Elastic fatigue

Viva ? voce
18


To find the wavelength of the laser beam, ?:
Distance between the screen and the grating, D = ------------?10
-2
m
Number of lines per meter length of the grating, N = --------------- Lines per meter
Sl. No.
Order of diffraction,
(m)
Reading of the diffracted image
(?10
-2
m)
?? ?? = ?????? ?1
(
?? ?? ?? )
(deg.)
? =
?????? ?? ?? ????
m

Left side
(xi)
Right side
(xr)
Mean
(xm)










Mean, ? = ---------------- m


FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
2


PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science and fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems and use this knowledge to acquire
higher education.
2. Core competence
To train the students in Engineering Physics so as to apply their knowledge and training to compare,
and to analyze various engineering industrial problems for finding solutions.
3. Breadth
To provide relevant training and experience to bridge the gap between theoretical learning and
practice that enables them to find solutions for the real time problems in industry and to design products.
4. Professionalism
To inculcate professional and effective communication skills, leadership qualities and team spirit for
the students to make them multi-faceted personalities and develop their ability to relate engineering issues
to broader social context.
5. Lifelong learning/ethics
To demonstrate and practice ethical and professional responsibilities in the industry and society by
and large, through commitment and lifelong learning needed for successful professional career.





3


PROGRAMME OUTCOMES (POs)

a) To demonstrate and apply knowledge of Mathematics, Science and Engineering fundamentals in
Engineering physics
b) To determine the Moment of Inertia of given disc and Rigidity modulus of the given wire using
Torsional Pendulum
c) To determine Young?s modulus of a given bar using Non-Uniform bending
d) To utilize laser source and grating to estimate the wave length, particle size of given powder and
Numerical Aperture & acceptance angle of given optical fiber
e) To find the Thermal conductivity of a bad conductor using Lee?s Disc method
f) To Measure the velocity of ultrasonic wave in a liquid and compressibility of the liquid usingultrasonic
Interferometer
g) To determine the wavelength of Hg source using grating and spectrometer
h) To find the thickness of a thin wire using Air- wedge method
i) To participate and succeed in competitive exams and visualize and work on laboratory and
multidisciplinary tasks











4


BS 8161 ? PHYSICSLABORATORY
(Common to all branches of B.E. / B.TechProgrammes)
SYLLABUS


To introduce different experiments to test basic understanding of physics concepts applied in optics, thermal
physics, properties of matter and liquids.

LIST OF EXPERIMENTS: PHYSICS LABORATORY(Any 5 Experiments)
1. Determination of Rigidity modulus ? Torsion pendulum
2. Determination of Young? s modulus by Non uniform bending method
3. (a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
4. Determination of thermal conductivity of a bad conductor ? Lee?s Disc method.
5. Determination of velocity of sound and compressibility of liquid ? Ultrasonic interferometer
6. Determination of wavelength of mercury spectrum ? spectrometer grating
7. Determination of band gap of a semiconductor
8. Determination of thickness of a thin wire ? Air wedge method




Completion of the course, the students will be able to: apply physics principles of optics and thermal physics
to evaluate engineering properties of materials.


COURSE OUTCOMES
COURSE OBJECTIVES
5

BS 8161 ? PHYSICS LABORATORY
CONTENTS

Sl.No. Name of the Experiment (any 5 experiments)
Page
No.
1.
Determination of Rigidity modulus ? Torsion pendulum
6
2.
Determination of Young ?s modulus by Non uniform bending method
12
3.
(a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
18
4.
Determination of thermal conductivity of a bad conductor ? Lee ?s Disc method.
28
5.
Determination of velocity of sound and compressibility of liquid ? Ultrasonic
interferometer
37
6.
Determination of wavelength of mercury spectrum ? spectrometer grating
42
7.
Determination of thickness of a thin wire ? Air wedge method
48
MEASURING INSTRUMENTS
M1 Screw gauge 54
M2 Vernier Calipers 58
M3 Travelling Microscope 62
M4 Spectrometer 66








6

TORSIONAL PENDULUM










7

Expt. No.1 TORSIONAL PENDULUM

AIM:
To determine the moment of inertia of the given disc and hence to determine the rigidity modulus of
the material of the given suspension wire by torsional oscillations
APPARATUS REQUIRED:
Torsional pendulum, two equal masses, stop clock, screw gauge and meter scale

FORMULA:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
where
m ?mass of the cylinder placed on the disc (kg)
To ?period of the pendulum for a length of l without mass (s)
T1?period of the pendulum for the same length when mass m is placed at a distance d 1
from the center of the suspension wire (s)
T2?period of the pendulum for the same length when mass m is placed at a distance d 2
from the center of the suspension wire (s)
a ? radius of the suspension wire (m)




8

1. To determine the time period of the disc:
Length of the wire (l)= --------
2
10
?
? m
Position of the equal
masses
Time for 10 oscillations Time period
(one oscillation)
s
Trial-1
s
Trial-2
s
Mean
s
Without any masses T0
With masses at
d1 = x10
-2
m
T1
With masses at
d2 = x10
-2
m
T2

2. To determine the radius of the wire:
Least count =0 .01 mm. Zero Error ZE = --------- divisions
Zero Correction ZC = ---------- mm

Sl.No.
Pitch Scale
Reading
PSR
3
10
?
? m
Head Scale
Coincidence
HSC
div
Observed reading
OR = PSR + (HSCXLC)
3
10
?
? m
Correct reading
CR = OR ? ZC
3
10
?
? m




Mean = ----------------
3
10
?
? m



9

PROCEDURE:
Torsional pendulum is suspended from vertical chuck. The length of the suspension wire is measured
between the vertical chuck and the chuck attached to the uniform circular disc (i). The circular disc is twisted
slightly without masses on the disc. Now it executes torsional oscillations. Care is taken to see that the disc
oscillates without wobbling. Time taken for 20 oscillations is noted with the help of a stop clock. Two trials are
taken. The average of these two trial readings is calculated from which the period of oscillations is found out
as T0.
Two identical cylindrical masses each of mass m are symmetrically placed on the disc on either side
of the wire at a distance d from the center of the disc. As before the disc is gently twisted. Time taken for 20
oscillations is noted from which the period of oscillation is calculated as T1.
The cylindrical masses are placed at a distance d2 from the center and the experiment is repeated.
The mean time period of oscillations is calculated T2.
The diameter of the specimen wire is measured accurately with the help of the screw gauge, at
various places on the wire. The average diameter and hence the radius of the wire is calculated as r.
Moment of inertia and the rigidity modulus are determined by the substituting the value of m, T 0, T1, T2,
T3, and l in the formula.










10

CALCULATION:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2

Mass of cylindrical mass, m = ----------- ? 10
-3
kg
Closest distance of the mass from the centre of the suspension wire, d1 = ------------ ? 10
-2
m
Farthest distance of the mass from the centre of suspension wire, d2= ------------? 10
-2
m
Period of oscillation without mass, To = ------------- s
Period of oscillation with mass at d1, T1= ------------ s
Period of oscillation with mass at d2, T2 = ------------- s

Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
= --------------- kg m
2
= --------------- kg m
2

Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
Moment of inertia, I = ------------------ kg m
2
Length of the wire, l = ------------------- ? 10
-2
m
Time of oscillation, To = ------------------ s
Radius of the wire, a = ------------------- ? 10
-3
m
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
= ----------------------
Rigidity modulus, n = ------------------- Nm
-2
11









RESULT:
(i)
The moment of inertia of the given circular disc, I = --------------- kg m
2
(ii)
The rigidity modulus of the material of the given wire, n = -------------- Nm
-2




1. State Hooke?s law.
2. Define ?Rigidity modulus
3. Define ?Moment of inertia
4. What is meant by torsional oscillation?
5. What is period of oscillation?
6. What is meant by twisting couple?
7. Define ? Shearing stress
8. Define ? Shearing strain
9. What is the unit of rigidity modulus?
10. What are the applications of torsional pendulum?


Viva ? voce
12


Young?s Modulus ? Non Uniform Bending
To determine depression (y):
L.C =.001cm M = ___________
3
10
?
? kg

Sl.No

Load


3
10
?
?
k
g
Microscope reading
Mean

2
10
?
? m
Depression
y for M kg

2
10
?
? m
Loading Unloading
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
1 W
2 W+50
3 W+100
4 W+150
5 W+200
6 W+250

Mean (y) = ----------
2
10
?
? m





13

Expt. No.2 YOUNG?S MODULUS BY NON ? UNIFORM BENDING
AIM:
To determine the young?s modulus of the material of the given bar, by non-uniform bending method
APPARATUS REQUIRED:
Travelling microscope, wooden bar, knife- edge, weights hanger, slotted weight, vernier calipers,
screw gauge and pin
FORMULA:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Where,
g ? acceleration due to gravity (9.8 ms
-2
)
l ? length of the bar between two knife edges (m)
b ? breadth of the bar (m)
d ? thickness of the bar (m)
y ? depressiont in the scale reading due to the change of mass M (m)
PROCEDURE:
The given wooden bar, for which young?s modulus is to be determined, is paced symmetrically on the
two knife edges. The distance between the knife edges is measured as the length of the bar (l). It is adjusted
to be, say, 60 cm. the weight hanger is suspended at the centre of the bar. A pin is held vertically at the
centre of the bar with the help of wax.
The given bar is brought to elastic mood by loading and unloading the bar with slotted weights in steps
of 50 g. This is repeated for two or three times. With the hanger as dead load W, the microscope is focused on
to the tip of the pin. The tangential screw of the microscope is adjusted so that the image of the tip of the pin
just touches the horizontal cross wire of the eyepiece. The main scale reading and the vernier scale
coincidence corresponding to this position are noted.
14

To find the breadth using vernier calipers, b:
Least count = ---------- cm Zero error = --------- div.
= ---------- ?10
-2
m Zero correction = ?ZE ?LC= --------- ?10
-2
m
Sl. No.

MSR
x 10
-2
m

VSC
div.
Observed reading
OR = MSR+(VSC ? LC)
x 10
-2
m
Correct Reading
CR = OR ? ZC
x 10
-2
m
1.

2.

3.


Mean, b = ------------------------?10
-2
m
To find the thickness using screw gauge, d:
Least count = ---------- mm Zero error = --------- div.
= ---------- ?10
-3
m Zero correction =ZE ?LC= --------- ?10
-3
m
Sl. No.

PSR
x 10
-3
m

HSC
div.
Observed reading
OR = PSR+ (HSC ? LC)
x 10
-3
m
Correct Reading
CR = OR ? ZC
x 10
-3
m
1.

2.

3.


Mean, d = ---------------------------?10
-3
m
15


The experiment is repeated by adding weights in steps of 50 g and every time the microscope is
adjusted for coincidence. The corresponding readings are noted. The experiment is repeated by unloading the
weights in steps of 50 g and the corresponding readings are tabulated. From this table, the shift in the scale
reading, say y, for a change of mass M is found out.
The breadth of the bar is measured at various points with the help of vernier calipers. Similarly the
thickness of the bar is measured by screw gauge. Substituting the values of M, y, l, d, b and g in the formula,
the young?s modulus of the material of the given bar is calculated.

















16

CALCULATION:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Acceleration due to gravity, g = 9.8 ms
-2
Length of the bar between two knife edges, l = ------------ ?10
-2
m
Breadth of the bar, b = ----------- ?10
-2
m
Thickness of the bar, d = ----------- ?10
-3
m
y = -----------?10
-2
m
E =
???? ?? 2
4?? ?? 3
?? Nm
-2

= ---------------
Young?s modulus, E = ----------- Nm
-2












17








RESULT:
Young?s modulus of the material of the given bar, E = ---------- Nm
-2


1. Define ? Young?s modulus
2. What is meant by Non-uniform bending?
3. Define ? Stress and strain
4. State Hooke?s law.
5. Define ? Neutral axis
6. What is the SI unit of young?s modulus?
7. Define ? Elastic limit
8. Define ? Elasticity
9. What are the factors affecting elasticity?
10. Define ? Elastic fatigue

Viva ? voce
18


To find the wavelength of the laser beam, ?:
Distance between the screen and the grating, D = ------------?10
-2
m
Number of lines per meter length of the grating, N = --------------- Lines per meter
Sl. No.
Order of diffraction,
(m)
Reading of the diffracted image
(?10
-2
m)
?? ?? = ?????? ?1
(
?? ?? ?? )
(deg.)
? =
?????? ?? ?? ????
m

Left side
(xi)
Right side
(xr)
Mean
(xm)










Mean, ? = ---------------- m


19

Expt. No.3(a) WAVELENGTH OF LASER LIGHT AND PARTICLE SIZE


AIM:
(i) To determine the wavelength of the given laser light.
(ii) To determine size of the given particle.
APPARATUS REQUIRED:
Diode laser, grating, screen, given micro particles, scale and screen.
FORMULAE:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
(ii) Grain size or diameter of the grain, 2d =
?????? ?? ?? m
Where
?? ?? ?angle of diffraction (deg.)
M ?order of diffraction (No unit)
N ?number of lines per metre length of the grating (m
-3
)
n ? order of diffraction (no unit)
? ? wavelength of laser light used (m)
D ? distance between the glass plate and the screen (m)
?? ?? - distance between the central bright spot and the nth fringe (m)
PROCEDURE:
TO FIND THE WAVELENGTH OF THE GIVEN LASER LIGHT:
The laser source, grating and screen are placed properly as shown in figure. The diode laser is kept
horizontally and switched on. Extreme care should be taken to avoid direct exposure of laser light on eyes.
FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
2


PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science and fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems and use this knowledge to acquire
higher education.
2. Core competence
To train the students in Engineering Physics so as to apply their knowledge and training to compare,
and to analyze various engineering industrial problems for finding solutions.
3. Breadth
To provide relevant training and experience to bridge the gap between theoretical learning and
practice that enables them to find solutions for the real time problems in industry and to design products.
4. Professionalism
To inculcate professional and effective communication skills, leadership qualities and team spirit for
the students to make them multi-faceted personalities and develop their ability to relate engineering issues
to broader social context.
5. Lifelong learning/ethics
To demonstrate and practice ethical and professional responsibilities in the industry and society by
and large, through commitment and lifelong learning needed for successful professional career.





3


PROGRAMME OUTCOMES (POs)

a) To demonstrate and apply knowledge of Mathematics, Science and Engineering fundamentals in
Engineering physics
b) To determine the Moment of Inertia of given disc and Rigidity modulus of the given wire using
Torsional Pendulum
c) To determine Young?s modulus of a given bar using Non-Uniform bending
d) To utilize laser source and grating to estimate the wave length, particle size of given powder and
Numerical Aperture & acceptance angle of given optical fiber
e) To find the Thermal conductivity of a bad conductor using Lee?s Disc method
f) To Measure the velocity of ultrasonic wave in a liquid and compressibility of the liquid usingultrasonic
Interferometer
g) To determine the wavelength of Hg source using grating and spectrometer
h) To find the thickness of a thin wire using Air- wedge method
i) To participate and succeed in competitive exams and visualize and work on laboratory and
multidisciplinary tasks











4


BS 8161 ? PHYSICSLABORATORY
(Common to all branches of B.E. / B.TechProgrammes)
SYLLABUS


To introduce different experiments to test basic understanding of physics concepts applied in optics, thermal
physics, properties of matter and liquids.

LIST OF EXPERIMENTS: PHYSICS LABORATORY(Any 5 Experiments)
1. Determination of Rigidity modulus ? Torsion pendulum
2. Determination of Young? s modulus by Non uniform bending method
3. (a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
4. Determination of thermal conductivity of a bad conductor ? Lee?s Disc method.
5. Determination of velocity of sound and compressibility of liquid ? Ultrasonic interferometer
6. Determination of wavelength of mercury spectrum ? spectrometer grating
7. Determination of band gap of a semiconductor
8. Determination of thickness of a thin wire ? Air wedge method




Completion of the course, the students will be able to: apply physics principles of optics and thermal physics
to evaluate engineering properties of materials.


COURSE OUTCOMES
COURSE OBJECTIVES
5

BS 8161 ? PHYSICS LABORATORY
CONTENTS

Sl.No. Name of the Experiment (any 5 experiments)
Page
No.
1.
Determination of Rigidity modulus ? Torsion pendulum
6
2.
Determination of Young ?s modulus by Non uniform bending method
12
3.
(a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
18
4.
Determination of thermal conductivity of a bad conductor ? Lee ?s Disc method.
28
5.
Determination of velocity of sound and compressibility of liquid ? Ultrasonic
interferometer
37
6.
Determination of wavelength of mercury spectrum ? spectrometer grating
42
7.
Determination of thickness of a thin wire ? Air wedge method
48
MEASURING INSTRUMENTS
M1 Screw gauge 54
M2 Vernier Calipers 58
M3 Travelling Microscope 62
M4 Spectrometer 66








6

TORSIONAL PENDULUM










7

Expt. No.1 TORSIONAL PENDULUM

AIM:
To determine the moment of inertia of the given disc and hence to determine the rigidity modulus of
the material of the given suspension wire by torsional oscillations
APPARATUS REQUIRED:
Torsional pendulum, two equal masses, stop clock, screw gauge and meter scale

FORMULA:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
where
m ?mass of the cylinder placed on the disc (kg)
To ?period of the pendulum for a length of l without mass (s)
T1?period of the pendulum for the same length when mass m is placed at a distance d 1
from the center of the suspension wire (s)
T2?period of the pendulum for the same length when mass m is placed at a distance d 2
from the center of the suspension wire (s)
a ? radius of the suspension wire (m)




8

1. To determine the time period of the disc:
Length of the wire (l)= --------
2
10
?
? m
Position of the equal
masses
Time for 10 oscillations Time period
(one oscillation)
s
Trial-1
s
Trial-2
s
Mean
s
Without any masses T0
With masses at
d1 = x10
-2
m
T1
With masses at
d2 = x10
-2
m
T2

2. To determine the radius of the wire:
Least count =0 .01 mm. Zero Error ZE = --------- divisions
Zero Correction ZC = ---------- mm

Sl.No.
Pitch Scale
Reading
PSR
3
10
?
? m
Head Scale
Coincidence
HSC
div
Observed reading
OR = PSR + (HSCXLC)
3
10
?
? m
Correct reading
CR = OR ? ZC
3
10
?
? m




Mean = ----------------
3
10
?
? m



9

PROCEDURE:
Torsional pendulum is suspended from vertical chuck. The length of the suspension wire is measured
between the vertical chuck and the chuck attached to the uniform circular disc (i). The circular disc is twisted
slightly without masses on the disc. Now it executes torsional oscillations. Care is taken to see that the disc
oscillates without wobbling. Time taken for 20 oscillations is noted with the help of a stop clock. Two trials are
taken. The average of these two trial readings is calculated from which the period of oscillations is found out
as T0.
Two identical cylindrical masses each of mass m are symmetrically placed on the disc on either side
of the wire at a distance d from the center of the disc. As before the disc is gently twisted. Time taken for 20
oscillations is noted from which the period of oscillation is calculated as T1.
The cylindrical masses are placed at a distance d2 from the center and the experiment is repeated.
The mean time period of oscillations is calculated T2.
The diameter of the specimen wire is measured accurately with the help of the screw gauge, at
various places on the wire. The average diameter and hence the radius of the wire is calculated as r.
Moment of inertia and the rigidity modulus are determined by the substituting the value of m, T 0, T1, T2,
T3, and l in the formula.










10

CALCULATION:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2

Mass of cylindrical mass, m = ----------- ? 10
-3
kg
Closest distance of the mass from the centre of the suspension wire, d1 = ------------ ? 10
-2
m
Farthest distance of the mass from the centre of suspension wire, d2= ------------? 10
-2
m
Period of oscillation without mass, To = ------------- s
Period of oscillation with mass at d1, T1= ------------ s
Period of oscillation with mass at d2, T2 = ------------- s

Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
= --------------- kg m
2
= --------------- kg m
2

Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
Moment of inertia, I = ------------------ kg m
2
Length of the wire, l = ------------------- ? 10
-2
m
Time of oscillation, To = ------------------ s
Radius of the wire, a = ------------------- ? 10
-3
m
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
= ----------------------
Rigidity modulus, n = ------------------- Nm
-2
11









RESULT:
(i)
The moment of inertia of the given circular disc, I = --------------- kg m
2
(ii)
The rigidity modulus of the material of the given wire, n = -------------- Nm
-2




1. State Hooke?s law.
2. Define ?Rigidity modulus
3. Define ?Moment of inertia
4. What is meant by torsional oscillation?
5. What is period of oscillation?
6. What is meant by twisting couple?
7. Define ? Shearing stress
8. Define ? Shearing strain
9. What is the unit of rigidity modulus?
10. What are the applications of torsional pendulum?


Viva ? voce
12


Young?s Modulus ? Non Uniform Bending
To determine depression (y):
L.C =.001cm M = ___________
3
10
?
? kg

Sl.No

Load


3
10
?
?
k
g
Microscope reading
Mean

2
10
?
? m
Depression
y for M kg

2
10
?
? m
Loading Unloading
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
1 W
2 W+50
3 W+100
4 W+150
5 W+200
6 W+250

Mean (y) = ----------
2
10
?
? m





13

Expt. No.2 YOUNG?S MODULUS BY NON ? UNIFORM BENDING
AIM:
To determine the young?s modulus of the material of the given bar, by non-uniform bending method
APPARATUS REQUIRED:
Travelling microscope, wooden bar, knife- edge, weights hanger, slotted weight, vernier calipers,
screw gauge and pin
FORMULA:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Where,
g ? acceleration due to gravity (9.8 ms
-2
)
l ? length of the bar between two knife edges (m)
b ? breadth of the bar (m)
d ? thickness of the bar (m)
y ? depressiont in the scale reading due to the change of mass M (m)
PROCEDURE:
The given wooden bar, for which young?s modulus is to be determined, is paced symmetrically on the
two knife edges. The distance between the knife edges is measured as the length of the bar (l). It is adjusted
to be, say, 60 cm. the weight hanger is suspended at the centre of the bar. A pin is held vertically at the
centre of the bar with the help of wax.
The given bar is brought to elastic mood by loading and unloading the bar with slotted weights in steps
of 50 g. This is repeated for two or three times. With the hanger as dead load W, the microscope is focused on
to the tip of the pin. The tangential screw of the microscope is adjusted so that the image of the tip of the pin
just touches the horizontal cross wire of the eyepiece. The main scale reading and the vernier scale
coincidence corresponding to this position are noted.
14

To find the breadth using vernier calipers, b:
Least count = ---------- cm Zero error = --------- div.
= ---------- ?10
-2
m Zero correction = ?ZE ?LC= --------- ?10
-2
m
Sl. No.

MSR
x 10
-2
m

VSC
div.
Observed reading
OR = MSR+(VSC ? LC)
x 10
-2
m
Correct Reading
CR = OR ? ZC
x 10
-2
m
1.

2.

3.


Mean, b = ------------------------?10
-2
m
To find the thickness using screw gauge, d:
Least count = ---------- mm Zero error = --------- div.
= ---------- ?10
-3
m Zero correction =ZE ?LC= --------- ?10
-3
m
Sl. No.

PSR
x 10
-3
m

HSC
div.
Observed reading
OR = PSR+ (HSC ? LC)
x 10
-3
m
Correct Reading
CR = OR ? ZC
x 10
-3
m
1.

2.

3.


Mean, d = ---------------------------?10
-3
m
15


The experiment is repeated by adding weights in steps of 50 g and every time the microscope is
adjusted for coincidence. The corresponding readings are noted. The experiment is repeated by unloading the
weights in steps of 50 g and the corresponding readings are tabulated. From this table, the shift in the scale
reading, say y, for a change of mass M is found out.
The breadth of the bar is measured at various points with the help of vernier calipers. Similarly the
thickness of the bar is measured by screw gauge. Substituting the values of M, y, l, d, b and g in the formula,
the young?s modulus of the material of the given bar is calculated.

















16

CALCULATION:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Acceleration due to gravity, g = 9.8 ms
-2
Length of the bar between two knife edges, l = ------------ ?10
-2
m
Breadth of the bar, b = ----------- ?10
-2
m
Thickness of the bar, d = ----------- ?10
-3
m
y = -----------?10
-2
m
E =
???? ?? 2
4?? ?? 3
?? Nm
-2

= ---------------
Young?s modulus, E = ----------- Nm
-2












17








RESULT:
Young?s modulus of the material of the given bar, E = ---------- Nm
-2


1. Define ? Young?s modulus
2. What is meant by Non-uniform bending?
3. Define ? Stress and strain
4. State Hooke?s law.
5. Define ? Neutral axis
6. What is the SI unit of young?s modulus?
7. Define ? Elastic limit
8. Define ? Elasticity
9. What are the factors affecting elasticity?
10. Define ? Elastic fatigue

Viva ? voce
18


To find the wavelength of the laser beam, ?:
Distance between the screen and the grating, D = ------------?10
-2
m
Number of lines per meter length of the grating, N = --------------- Lines per meter
Sl. No.
Order of diffraction,
(m)
Reading of the diffracted image
(?10
-2
m)
?? ?? = ?????? ?1
(
?? ?? ?? )
(deg.)
? =
?????? ?? ?? ????
m

Left side
(xi)
Right side
(xr)
Mean
(xm)










Mean, ? = ---------------- m


19

Expt. No.3(a) WAVELENGTH OF LASER LIGHT AND PARTICLE SIZE


AIM:
(i) To determine the wavelength of the given laser light.
(ii) To determine size of the given particle.
APPARATUS REQUIRED:
Diode laser, grating, screen, given micro particles, scale and screen.
FORMULAE:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
(ii) Grain size or diameter of the grain, 2d =
?????? ?? ?? m
Where
?? ?? ?angle of diffraction (deg.)
M ?order of diffraction (No unit)
N ?number of lines per metre length of the grating (m
-3
)
n ? order of diffraction (no unit)
? ? wavelength of laser light used (m)
D ? distance between the glass plate and the screen (m)
?? ?? - distance between the central bright spot and the nth fringe (m)
PROCEDURE:
TO FIND THE WAVELENGTH OF THE GIVEN LASER LIGHT:
The laser source, grating and screen are placed properly as shown in figure. The diode laser is kept
horizontally and switched on. Extreme care should be taken to avoid direct exposure of laser light on eyes.
20











FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
2


PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science and fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems and use this knowledge to acquire
higher education.
2. Core competence
To train the students in Engineering Physics so as to apply their knowledge and training to compare,
and to analyze various engineering industrial problems for finding solutions.
3. Breadth
To provide relevant training and experience to bridge the gap between theoretical learning and
practice that enables them to find solutions for the real time problems in industry and to design products.
4. Professionalism
To inculcate professional and effective communication skills, leadership qualities and team spirit for
the students to make them multi-faceted personalities and develop their ability to relate engineering issues
to broader social context.
5. Lifelong learning/ethics
To demonstrate and practice ethical and professional responsibilities in the industry and society by
and large, through commitment and lifelong learning needed for successful professional career.





3


PROGRAMME OUTCOMES (POs)

a) To demonstrate and apply knowledge of Mathematics, Science and Engineering fundamentals in
Engineering physics
b) To determine the Moment of Inertia of given disc and Rigidity modulus of the given wire using
Torsional Pendulum
c) To determine Young?s modulus of a given bar using Non-Uniform bending
d) To utilize laser source and grating to estimate the wave length, particle size of given powder and
Numerical Aperture & acceptance angle of given optical fiber
e) To find the Thermal conductivity of a bad conductor using Lee?s Disc method
f) To Measure the velocity of ultrasonic wave in a liquid and compressibility of the liquid usingultrasonic
Interferometer
g) To determine the wavelength of Hg source using grating and spectrometer
h) To find the thickness of a thin wire using Air- wedge method
i) To participate and succeed in competitive exams and visualize and work on laboratory and
multidisciplinary tasks











4


BS 8161 ? PHYSICSLABORATORY
(Common to all branches of B.E. / B.TechProgrammes)
SYLLABUS


To introduce different experiments to test basic understanding of physics concepts applied in optics, thermal
physics, properties of matter and liquids.

LIST OF EXPERIMENTS: PHYSICS LABORATORY(Any 5 Experiments)
1. Determination of Rigidity modulus ? Torsion pendulum
2. Determination of Young? s modulus by Non uniform bending method
3. (a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
4. Determination of thermal conductivity of a bad conductor ? Lee?s Disc method.
5. Determination of velocity of sound and compressibility of liquid ? Ultrasonic interferometer
6. Determination of wavelength of mercury spectrum ? spectrometer grating
7. Determination of band gap of a semiconductor
8. Determination of thickness of a thin wire ? Air wedge method




Completion of the course, the students will be able to: apply physics principles of optics and thermal physics
to evaluate engineering properties of materials.


COURSE OUTCOMES
COURSE OBJECTIVES
5

BS 8161 ? PHYSICS LABORATORY
CONTENTS

Sl.No. Name of the Experiment (any 5 experiments)
Page
No.
1.
Determination of Rigidity modulus ? Torsion pendulum
6
2.
Determination of Young ?s modulus by Non uniform bending method
12
3.
(a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
18
4.
Determination of thermal conductivity of a bad conductor ? Lee ?s Disc method.
28
5.
Determination of velocity of sound and compressibility of liquid ? Ultrasonic
interferometer
37
6.
Determination of wavelength of mercury spectrum ? spectrometer grating
42
7.
Determination of thickness of a thin wire ? Air wedge method
48
MEASURING INSTRUMENTS
M1 Screw gauge 54
M2 Vernier Calipers 58
M3 Travelling Microscope 62
M4 Spectrometer 66








6

TORSIONAL PENDULUM










7

Expt. No.1 TORSIONAL PENDULUM

AIM:
To determine the moment of inertia of the given disc and hence to determine the rigidity modulus of
the material of the given suspension wire by torsional oscillations
APPARATUS REQUIRED:
Torsional pendulum, two equal masses, stop clock, screw gauge and meter scale

FORMULA:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
where
m ?mass of the cylinder placed on the disc (kg)
To ?period of the pendulum for a length of l without mass (s)
T1?period of the pendulum for the same length when mass m is placed at a distance d 1
from the center of the suspension wire (s)
T2?period of the pendulum for the same length when mass m is placed at a distance d 2
from the center of the suspension wire (s)
a ? radius of the suspension wire (m)




8

1. To determine the time period of the disc:
Length of the wire (l)= --------
2
10
?
? m
Position of the equal
masses
Time for 10 oscillations Time period
(one oscillation)
s
Trial-1
s
Trial-2
s
Mean
s
Without any masses T0
With masses at
d1 = x10
-2
m
T1
With masses at
d2 = x10
-2
m
T2

2. To determine the radius of the wire:
Least count =0 .01 mm. Zero Error ZE = --------- divisions
Zero Correction ZC = ---------- mm

Sl.No.
Pitch Scale
Reading
PSR
3
10
?
? m
Head Scale
Coincidence
HSC
div
Observed reading
OR = PSR + (HSCXLC)
3
10
?
? m
Correct reading
CR = OR ? ZC
3
10
?
? m




Mean = ----------------
3
10
?
? m



9

PROCEDURE:
Torsional pendulum is suspended from vertical chuck. The length of the suspension wire is measured
between the vertical chuck and the chuck attached to the uniform circular disc (i). The circular disc is twisted
slightly without masses on the disc. Now it executes torsional oscillations. Care is taken to see that the disc
oscillates without wobbling. Time taken for 20 oscillations is noted with the help of a stop clock. Two trials are
taken. The average of these two trial readings is calculated from which the period of oscillations is found out
as T0.
Two identical cylindrical masses each of mass m are symmetrically placed on the disc on either side
of the wire at a distance d from the center of the disc. As before the disc is gently twisted. Time taken for 20
oscillations is noted from which the period of oscillation is calculated as T1.
The cylindrical masses are placed at a distance d2 from the center and the experiment is repeated.
The mean time period of oscillations is calculated T2.
The diameter of the specimen wire is measured accurately with the help of the screw gauge, at
various places on the wire. The average diameter and hence the radius of the wire is calculated as r.
Moment of inertia and the rigidity modulus are determined by the substituting the value of m, T 0, T1, T2,
T3, and l in the formula.










10

CALCULATION:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2

Mass of cylindrical mass, m = ----------- ? 10
-3
kg
Closest distance of the mass from the centre of the suspension wire, d1 = ------------ ? 10
-2
m
Farthest distance of the mass from the centre of suspension wire, d2= ------------? 10
-2
m
Period of oscillation without mass, To = ------------- s
Period of oscillation with mass at d1, T1= ------------ s
Period of oscillation with mass at d2, T2 = ------------- s

Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
= --------------- kg m
2
= --------------- kg m
2

Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
Moment of inertia, I = ------------------ kg m
2
Length of the wire, l = ------------------- ? 10
-2
m
Time of oscillation, To = ------------------ s
Radius of the wire, a = ------------------- ? 10
-3
m
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
= ----------------------
Rigidity modulus, n = ------------------- Nm
-2
11









RESULT:
(i)
The moment of inertia of the given circular disc, I = --------------- kg m
2
(ii)
The rigidity modulus of the material of the given wire, n = -------------- Nm
-2




1. State Hooke?s law.
2. Define ?Rigidity modulus
3. Define ?Moment of inertia
4. What is meant by torsional oscillation?
5. What is period of oscillation?
6. What is meant by twisting couple?
7. Define ? Shearing stress
8. Define ? Shearing strain
9. What is the unit of rigidity modulus?
10. What are the applications of torsional pendulum?


Viva ? voce
12


Young?s Modulus ? Non Uniform Bending
To determine depression (y):
L.C =.001cm M = ___________
3
10
?
? kg

Sl.No

Load


3
10
?
?
k
g
Microscope reading
Mean

2
10
?
? m
Depression
y for M kg

2
10
?
? m
Loading Unloading
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
1 W
2 W+50
3 W+100
4 W+150
5 W+200
6 W+250

Mean (y) = ----------
2
10
?
? m





13

Expt. No.2 YOUNG?S MODULUS BY NON ? UNIFORM BENDING
AIM:
To determine the young?s modulus of the material of the given bar, by non-uniform bending method
APPARATUS REQUIRED:
Travelling microscope, wooden bar, knife- edge, weights hanger, slotted weight, vernier calipers,
screw gauge and pin
FORMULA:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Where,
g ? acceleration due to gravity (9.8 ms
-2
)
l ? length of the bar between two knife edges (m)
b ? breadth of the bar (m)
d ? thickness of the bar (m)
y ? depressiont in the scale reading due to the change of mass M (m)
PROCEDURE:
The given wooden bar, for which young?s modulus is to be determined, is paced symmetrically on the
two knife edges. The distance between the knife edges is measured as the length of the bar (l). It is adjusted
to be, say, 60 cm. the weight hanger is suspended at the centre of the bar. A pin is held vertically at the
centre of the bar with the help of wax.
The given bar is brought to elastic mood by loading and unloading the bar with slotted weights in steps
of 50 g. This is repeated for two or three times. With the hanger as dead load W, the microscope is focused on
to the tip of the pin. The tangential screw of the microscope is adjusted so that the image of the tip of the pin
just touches the horizontal cross wire of the eyepiece. The main scale reading and the vernier scale
coincidence corresponding to this position are noted.
14

To find the breadth using vernier calipers, b:
Least count = ---------- cm Zero error = --------- div.
= ---------- ?10
-2
m Zero correction = ?ZE ?LC= --------- ?10
-2
m
Sl. No.

MSR
x 10
-2
m

VSC
div.
Observed reading
OR = MSR+(VSC ? LC)
x 10
-2
m
Correct Reading
CR = OR ? ZC
x 10
-2
m
1.

2.

3.


Mean, b = ------------------------?10
-2
m
To find the thickness using screw gauge, d:
Least count = ---------- mm Zero error = --------- div.
= ---------- ?10
-3
m Zero correction =ZE ?LC= --------- ?10
-3
m
Sl. No.

PSR
x 10
-3
m

HSC
div.
Observed reading
OR = PSR+ (HSC ? LC)
x 10
-3
m
Correct Reading
CR = OR ? ZC
x 10
-3
m
1.

2.

3.


Mean, d = ---------------------------?10
-3
m
15


The experiment is repeated by adding weights in steps of 50 g and every time the microscope is
adjusted for coincidence. The corresponding readings are noted. The experiment is repeated by unloading the
weights in steps of 50 g and the corresponding readings are tabulated. From this table, the shift in the scale
reading, say y, for a change of mass M is found out.
The breadth of the bar is measured at various points with the help of vernier calipers. Similarly the
thickness of the bar is measured by screw gauge. Substituting the values of M, y, l, d, b and g in the formula,
the young?s modulus of the material of the given bar is calculated.

















16

CALCULATION:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Acceleration due to gravity, g = 9.8 ms
-2
Length of the bar between two knife edges, l = ------------ ?10
-2
m
Breadth of the bar, b = ----------- ?10
-2
m
Thickness of the bar, d = ----------- ?10
-3
m
y = -----------?10
-2
m
E =
???? ?? 2
4?? ?? 3
?? Nm
-2

= ---------------
Young?s modulus, E = ----------- Nm
-2












17








RESULT:
Young?s modulus of the material of the given bar, E = ---------- Nm
-2


1. Define ? Young?s modulus
2. What is meant by Non-uniform bending?
3. Define ? Stress and strain
4. State Hooke?s law.
5. Define ? Neutral axis
6. What is the SI unit of young?s modulus?
7. Define ? Elastic limit
8. Define ? Elasticity
9. What are the factors affecting elasticity?
10. Define ? Elastic fatigue

Viva ? voce
18


To find the wavelength of the laser beam, ?:
Distance between the screen and the grating, D = ------------?10
-2
m
Number of lines per meter length of the grating, N = --------------- Lines per meter
Sl. No.
Order of diffraction,
(m)
Reading of the diffracted image
(?10
-2
m)
?? ?? = ?????? ?1
(
?? ?? ?? )
(deg.)
? =
?????? ?? ?? ????
m

Left side
(xi)
Right side
(xr)
Mean
(xm)










Mean, ? = ---------------- m


19

Expt. No.3(a) WAVELENGTH OF LASER LIGHT AND PARTICLE SIZE


AIM:
(i) To determine the wavelength of the given laser light.
(ii) To determine size of the given particle.
APPARATUS REQUIRED:
Diode laser, grating, screen, given micro particles, scale and screen.
FORMULAE:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
(ii) Grain size or diameter of the grain, 2d =
?????? ?? ?? m
Where
?? ?? ?angle of diffraction (deg.)
M ?order of diffraction (No unit)
N ?number of lines per metre length of the grating (m
-3
)
n ? order of diffraction (no unit)
? ? wavelength of laser light used (m)
D ? distance between the glass plate and the screen (m)
?? ?? - distance between the central bright spot and the nth fringe (m)
PROCEDURE:
TO FIND THE WAVELENGTH OF THE GIVEN LASER LIGHT:
The laser source, grating and screen are placed properly as shown in figure. The diode laser is kept
horizontally and switched on. Extreme care should be taken to avoid direct exposure of laser light on eyes.
20











21

The grating is held normal to the laser beam by adjusting the grating in such a way that the reflected
laser beam from the grating coincides with incident laser beam. Now the diffracted laser spots of various
orders can be seen on the screen, placed on the other side of the grating.

The distance of the different orders on either side of the central spot are measured as x randxi and are
tabulated.The mean value of xrandxiare calculated as xm for the m
th
order diffracted light. The distance
between the grating and the screen is measured as D. Hence, the angle of diffraction for the m
th
order,
?? ?? = ?????? ?1
(
?? ?? ?? )
The experiment is repeated for different orders and the readings are tabulated. From the table, ? for
each order is calculated. Substituting the value of ?, the corresponding order of diffraction and the number of
lines per meter length of the grating, the wavelength is calculated.

TO FIND THE SIZE OF THE GIVEN MICRO PARTICLE:

The lycopodium powder having fine micro particles of nearly same size is sprinkled on a glass plate.
This glass plate is kept between laser source and screen.
Now the particles present in the glass plate diffract laser beam from the source. By adjusting the
distance between the glass plate and the screen, a circular fringe pattern is obtained on the screen with
different orders of fingers. Now distance between the screen and the glass plate (D) is measured.
The distance of the first order and the second order fringe from the centre of spot are also measured.
Using the formula, the particle size is found out. The experiment is repeated for different D values.
FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
2


PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science and fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems and use this knowledge to acquire
higher education.
2. Core competence
To train the students in Engineering Physics so as to apply their knowledge and training to compare,
and to analyze various engineering industrial problems for finding solutions.
3. Breadth
To provide relevant training and experience to bridge the gap between theoretical learning and
practice that enables them to find solutions for the real time problems in industry and to design products.
4. Professionalism
To inculcate professional and effective communication skills, leadership qualities and team spirit for
the students to make them multi-faceted personalities and develop their ability to relate engineering issues
to broader social context.
5. Lifelong learning/ethics
To demonstrate and practice ethical and professional responsibilities in the industry and society by
and large, through commitment and lifelong learning needed for successful professional career.





3


PROGRAMME OUTCOMES (POs)

a) To demonstrate and apply knowledge of Mathematics, Science and Engineering fundamentals in
Engineering physics
b) To determine the Moment of Inertia of given disc and Rigidity modulus of the given wire using
Torsional Pendulum
c) To determine Young?s modulus of a given bar using Non-Uniform bending
d) To utilize laser source and grating to estimate the wave length, particle size of given powder and
Numerical Aperture & acceptance angle of given optical fiber
e) To find the Thermal conductivity of a bad conductor using Lee?s Disc method
f) To Measure the velocity of ultrasonic wave in a liquid and compressibility of the liquid usingultrasonic
Interferometer
g) To determine the wavelength of Hg source using grating and spectrometer
h) To find the thickness of a thin wire using Air- wedge method
i) To participate and succeed in competitive exams and visualize and work on laboratory and
multidisciplinary tasks











4


BS 8161 ? PHYSICSLABORATORY
(Common to all branches of B.E. / B.TechProgrammes)
SYLLABUS


To introduce different experiments to test basic understanding of physics concepts applied in optics, thermal
physics, properties of matter and liquids.

LIST OF EXPERIMENTS: PHYSICS LABORATORY(Any 5 Experiments)
1. Determination of Rigidity modulus ? Torsion pendulum
2. Determination of Young? s modulus by Non uniform bending method
3. (a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
4. Determination of thermal conductivity of a bad conductor ? Lee?s Disc method.
5. Determination of velocity of sound and compressibility of liquid ? Ultrasonic interferometer
6. Determination of wavelength of mercury spectrum ? spectrometer grating
7. Determination of band gap of a semiconductor
8. Determination of thickness of a thin wire ? Air wedge method




Completion of the course, the students will be able to: apply physics principles of optics and thermal physics
to evaluate engineering properties of materials.


COURSE OUTCOMES
COURSE OBJECTIVES
5

BS 8161 ? PHYSICS LABORATORY
CONTENTS

Sl.No. Name of the Experiment (any 5 experiments)
Page
No.
1.
Determination of Rigidity modulus ? Torsion pendulum
6
2.
Determination of Young ?s modulus by Non uniform bending method
12
3.
(a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
18
4.
Determination of thermal conductivity of a bad conductor ? Lee ?s Disc method.
28
5.
Determination of velocity of sound and compressibility of liquid ? Ultrasonic
interferometer
37
6.
Determination of wavelength of mercury spectrum ? spectrometer grating
42
7.
Determination of thickness of a thin wire ? Air wedge method
48
MEASURING INSTRUMENTS
M1 Screw gauge 54
M2 Vernier Calipers 58
M3 Travelling Microscope 62
M4 Spectrometer 66








6

TORSIONAL PENDULUM










7

Expt. No.1 TORSIONAL PENDULUM

AIM:
To determine the moment of inertia of the given disc and hence to determine the rigidity modulus of
the material of the given suspension wire by torsional oscillations
APPARATUS REQUIRED:
Torsional pendulum, two equal masses, stop clock, screw gauge and meter scale

FORMULA:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
where
m ?mass of the cylinder placed on the disc (kg)
To ?period of the pendulum for a length of l without mass (s)
T1?period of the pendulum for the same length when mass m is placed at a distance d 1
from the center of the suspension wire (s)
T2?period of the pendulum for the same length when mass m is placed at a distance d 2
from the center of the suspension wire (s)
a ? radius of the suspension wire (m)




8

1. To determine the time period of the disc:
Length of the wire (l)= --------
2
10
?
? m
Position of the equal
masses
Time for 10 oscillations Time period
(one oscillation)
s
Trial-1
s
Trial-2
s
Mean
s
Without any masses T0
With masses at
d1 = x10
-2
m
T1
With masses at
d2 = x10
-2
m
T2

2. To determine the radius of the wire:
Least count =0 .01 mm. Zero Error ZE = --------- divisions
Zero Correction ZC = ---------- mm

Sl.No.
Pitch Scale
Reading
PSR
3
10
?
? m
Head Scale
Coincidence
HSC
div
Observed reading
OR = PSR + (HSCXLC)
3
10
?
? m
Correct reading
CR = OR ? ZC
3
10
?
? m




Mean = ----------------
3
10
?
? m



9

PROCEDURE:
Torsional pendulum is suspended from vertical chuck. The length of the suspension wire is measured
between the vertical chuck and the chuck attached to the uniform circular disc (i). The circular disc is twisted
slightly without masses on the disc. Now it executes torsional oscillations. Care is taken to see that the disc
oscillates without wobbling. Time taken for 20 oscillations is noted with the help of a stop clock. Two trials are
taken. The average of these two trial readings is calculated from which the period of oscillations is found out
as T0.
Two identical cylindrical masses each of mass m are symmetrically placed on the disc on either side
of the wire at a distance d from the center of the disc. As before the disc is gently twisted. Time taken for 20
oscillations is noted from which the period of oscillation is calculated as T1.
The cylindrical masses are placed at a distance d2 from the center and the experiment is repeated.
The mean time period of oscillations is calculated T2.
The diameter of the specimen wire is measured accurately with the help of the screw gauge, at
various places on the wire. The average diameter and hence the radius of the wire is calculated as r.
Moment of inertia and the rigidity modulus are determined by the substituting the value of m, T 0, T1, T2,
T3, and l in the formula.










10

CALCULATION:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2

Mass of cylindrical mass, m = ----------- ? 10
-3
kg
Closest distance of the mass from the centre of the suspension wire, d1 = ------------ ? 10
-2
m
Farthest distance of the mass from the centre of suspension wire, d2= ------------? 10
-2
m
Period of oscillation without mass, To = ------------- s
Period of oscillation with mass at d1, T1= ------------ s
Period of oscillation with mass at d2, T2 = ------------- s

Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
= --------------- kg m
2
= --------------- kg m
2

Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
Moment of inertia, I = ------------------ kg m
2
Length of the wire, l = ------------------- ? 10
-2
m
Time of oscillation, To = ------------------ s
Radius of the wire, a = ------------------- ? 10
-3
m
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
= ----------------------
Rigidity modulus, n = ------------------- Nm
-2
11









RESULT:
(i)
The moment of inertia of the given circular disc, I = --------------- kg m
2
(ii)
The rigidity modulus of the material of the given wire, n = -------------- Nm
-2




1. State Hooke?s law.
2. Define ?Rigidity modulus
3. Define ?Moment of inertia
4. What is meant by torsional oscillation?
5. What is period of oscillation?
6. What is meant by twisting couple?
7. Define ? Shearing stress
8. Define ? Shearing strain
9. What is the unit of rigidity modulus?
10. What are the applications of torsional pendulum?


Viva ? voce
12


Young?s Modulus ? Non Uniform Bending
To determine depression (y):
L.C =.001cm M = ___________
3
10
?
? kg

Sl.No

Load


3
10
?
?
k
g
Microscope reading
Mean

2
10
?
? m
Depression
y for M kg

2
10
?
? m
Loading Unloading
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
1 W
2 W+50
3 W+100
4 W+150
5 W+200
6 W+250

Mean (y) = ----------
2
10
?
? m





13

Expt. No.2 YOUNG?S MODULUS BY NON ? UNIFORM BENDING
AIM:
To determine the young?s modulus of the material of the given bar, by non-uniform bending method
APPARATUS REQUIRED:
Travelling microscope, wooden bar, knife- edge, weights hanger, slotted weight, vernier calipers,
screw gauge and pin
FORMULA:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Where,
g ? acceleration due to gravity (9.8 ms
-2
)
l ? length of the bar between two knife edges (m)
b ? breadth of the bar (m)
d ? thickness of the bar (m)
y ? depressiont in the scale reading due to the change of mass M (m)
PROCEDURE:
The given wooden bar, for which young?s modulus is to be determined, is paced symmetrically on the
two knife edges. The distance between the knife edges is measured as the length of the bar (l). It is adjusted
to be, say, 60 cm. the weight hanger is suspended at the centre of the bar. A pin is held vertically at the
centre of the bar with the help of wax.
The given bar is brought to elastic mood by loading and unloading the bar with slotted weights in steps
of 50 g. This is repeated for two or three times. With the hanger as dead load W, the microscope is focused on
to the tip of the pin. The tangential screw of the microscope is adjusted so that the image of the tip of the pin
just touches the horizontal cross wire of the eyepiece. The main scale reading and the vernier scale
coincidence corresponding to this position are noted.
14

To find the breadth using vernier calipers, b:
Least count = ---------- cm Zero error = --------- div.
= ---------- ?10
-2
m Zero correction = ?ZE ?LC= --------- ?10
-2
m
Sl. No.

MSR
x 10
-2
m

VSC
div.
Observed reading
OR = MSR+(VSC ? LC)
x 10
-2
m
Correct Reading
CR = OR ? ZC
x 10
-2
m
1.

2.

3.


Mean, b = ------------------------?10
-2
m
To find the thickness using screw gauge, d:
Least count = ---------- mm Zero error = --------- div.
= ---------- ?10
-3
m Zero correction =ZE ?LC= --------- ?10
-3
m
Sl. No.

PSR
x 10
-3
m

HSC
div.
Observed reading
OR = PSR+ (HSC ? LC)
x 10
-3
m
Correct Reading
CR = OR ? ZC
x 10
-3
m
1.

2.

3.


Mean, d = ---------------------------?10
-3
m
15


The experiment is repeated by adding weights in steps of 50 g and every time the microscope is
adjusted for coincidence. The corresponding readings are noted. The experiment is repeated by unloading the
weights in steps of 50 g and the corresponding readings are tabulated. From this table, the shift in the scale
reading, say y, for a change of mass M is found out.
The breadth of the bar is measured at various points with the help of vernier calipers. Similarly the
thickness of the bar is measured by screw gauge. Substituting the values of M, y, l, d, b and g in the formula,
the young?s modulus of the material of the given bar is calculated.

















16

CALCULATION:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Acceleration due to gravity, g = 9.8 ms
-2
Length of the bar between two knife edges, l = ------------ ?10
-2
m
Breadth of the bar, b = ----------- ?10
-2
m
Thickness of the bar, d = ----------- ?10
-3
m
y = -----------?10
-2
m
E =
???? ?? 2
4?? ?? 3
?? Nm
-2

= ---------------
Young?s modulus, E = ----------- Nm
-2












17








RESULT:
Young?s modulus of the material of the given bar, E = ---------- Nm
-2


1. Define ? Young?s modulus
2. What is meant by Non-uniform bending?
3. Define ? Stress and strain
4. State Hooke?s law.
5. Define ? Neutral axis
6. What is the SI unit of young?s modulus?
7. Define ? Elastic limit
8. Define ? Elasticity
9. What are the factors affecting elasticity?
10. Define ? Elastic fatigue

Viva ? voce
18


To find the wavelength of the laser beam, ?:
Distance between the screen and the grating, D = ------------?10
-2
m
Number of lines per meter length of the grating, N = --------------- Lines per meter
Sl. No.
Order of diffraction,
(m)
Reading of the diffracted image
(?10
-2
m)
?? ?? = ?????? ?1
(
?? ?? ?? )
(deg.)
? =
?????? ?? ?? ????
m

Left side
(xi)
Right side
(xr)
Mean
(xm)










Mean, ? = ---------------- m


19

Expt. No.3(a) WAVELENGTH OF LASER LIGHT AND PARTICLE SIZE


AIM:
(i) To determine the wavelength of the given laser light.
(ii) To determine size of the given particle.
APPARATUS REQUIRED:
Diode laser, grating, screen, given micro particles, scale and screen.
FORMULAE:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
(ii) Grain size or diameter of the grain, 2d =
?????? ?? ?? m
Where
?? ?? ?angle of diffraction (deg.)
M ?order of diffraction (No unit)
N ?number of lines per metre length of the grating (m
-3
)
n ? order of diffraction (no unit)
? ? wavelength of laser light used (m)
D ? distance between the glass plate and the screen (m)
?? ?? - distance between the central bright spot and the nth fringe (m)
PROCEDURE:
TO FIND THE WAVELENGTH OF THE GIVEN LASER LIGHT:
The laser source, grating and screen are placed properly as shown in figure. The diode laser is kept
horizontally and switched on. Extreme care should be taken to avoid direct exposure of laser light on eyes.
20











21

The grating is held normal to the laser beam by adjusting the grating in such a way that the reflected
laser beam from the grating coincides with incident laser beam. Now the diffracted laser spots of various
orders can be seen on the screen, placed on the other side of the grating.

The distance of the different orders on either side of the central spot are measured as x randxi and are
tabulated.The mean value of xrandxiare calculated as xm for the m
th
order diffracted light. The distance
between the grating and the screen is measured as D. Hence, the angle of diffraction for the m
th
order,
?? ?? = ?????? ?1
(
?? ?? ?? )
The experiment is repeated for different orders and the readings are tabulated. From the table, ? for
each order is calculated. Substituting the value of ?, the corresponding order of diffraction and the number of
lines per meter length of the grating, the wavelength is calculated.

TO FIND THE SIZE OF THE GIVEN MICRO PARTICLE:

The lycopodium powder having fine micro particles of nearly same size is sprinkled on a glass plate.
This glass plate is kept between laser source and screen.
Now the particles present in the glass plate diffract laser beam from the source. By adjusting the
distance between the glass plate and the screen, a circular fringe pattern is obtained on the screen with
different orders of fingers. Now distance between the screen and the glass plate (D) is measured.
The distance of the first order and the second order fringe from the centre of spot are also measured.
Using the formula, the particle size is found out. The experiment is repeated for different D values.
22

To find the size of the particle:

CALCULATION:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
Number of lines per metre in the grating, N = ------------ lines per metre.
First order, m1; ?? 1
= ------------
Wavelength, ? =
?????? ?? 1
????
= ------------
Second order, m2; ?? 2
= ------------
Wavelength, ? =
?????? ?? 2
????
= ------------
Third order, m3; ?? 3
= ------------
Wavelength, ? =
?????? ?? 3
????
= ------------
Fourth order, m4; ?? 4
= ------------
Wavelength, ? =
?????? ?? 4
????
= -------------
Fifth order, m5; ?? 5
= ------------

Sl.No



Distance between
screen and glass
plate(D)
2
10
?
? m
Order of
diffraction
(n)
Distance between the
central bright spot and n
th

fringe (xn )
2
10
?
? m
Particle size
2
n
nD
d
x
?
?
m






FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
2


PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science and fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems and use this knowledge to acquire
higher education.
2. Core competence
To train the students in Engineering Physics so as to apply their knowledge and training to compare,
and to analyze various engineering industrial problems for finding solutions.
3. Breadth
To provide relevant training and experience to bridge the gap between theoretical learning and
practice that enables them to find solutions for the real time problems in industry and to design products.
4. Professionalism
To inculcate professional and effective communication skills, leadership qualities and team spirit for
the students to make them multi-faceted personalities and develop their ability to relate engineering issues
to broader social context.
5. Lifelong learning/ethics
To demonstrate and practice ethical and professional responsibilities in the industry and society by
and large, through commitment and lifelong learning needed for successful professional career.





3


PROGRAMME OUTCOMES (POs)

a) To demonstrate and apply knowledge of Mathematics, Science and Engineering fundamentals in
Engineering physics
b) To determine the Moment of Inertia of given disc and Rigidity modulus of the given wire using
Torsional Pendulum
c) To determine Young?s modulus of a given bar using Non-Uniform bending
d) To utilize laser source and grating to estimate the wave length, particle size of given powder and
Numerical Aperture & acceptance angle of given optical fiber
e) To find the Thermal conductivity of a bad conductor using Lee?s Disc method
f) To Measure the velocity of ultrasonic wave in a liquid and compressibility of the liquid usingultrasonic
Interferometer
g) To determine the wavelength of Hg source using grating and spectrometer
h) To find the thickness of a thin wire using Air- wedge method
i) To participate and succeed in competitive exams and visualize and work on laboratory and
multidisciplinary tasks











4


BS 8161 ? PHYSICSLABORATORY
(Common to all branches of B.E. / B.TechProgrammes)
SYLLABUS


To introduce different experiments to test basic understanding of physics concepts applied in optics, thermal
physics, properties of matter and liquids.

LIST OF EXPERIMENTS: PHYSICS LABORATORY(Any 5 Experiments)
1. Determination of Rigidity modulus ? Torsion pendulum
2. Determination of Young? s modulus by Non uniform bending method
3. (a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
4. Determination of thermal conductivity of a bad conductor ? Lee?s Disc method.
5. Determination of velocity of sound and compressibility of liquid ? Ultrasonic interferometer
6. Determination of wavelength of mercury spectrum ? spectrometer grating
7. Determination of band gap of a semiconductor
8. Determination of thickness of a thin wire ? Air wedge method




Completion of the course, the students will be able to: apply physics principles of optics and thermal physics
to evaluate engineering properties of materials.


COURSE OUTCOMES
COURSE OBJECTIVES
5

BS 8161 ? PHYSICS LABORATORY
CONTENTS

Sl.No. Name of the Experiment (any 5 experiments)
Page
No.
1.
Determination of Rigidity modulus ? Torsion pendulum
6
2.
Determination of Young ?s modulus by Non uniform bending method
12
3.
(a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
18
4.
Determination of thermal conductivity of a bad conductor ? Lee ?s Disc method.
28
5.
Determination of velocity of sound and compressibility of liquid ? Ultrasonic
interferometer
37
6.
Determination of wavelength of mercury spectrum ? spectrometer grating
42
7.
Determination of thickness of a thin wire ? Air wedge method
48
MEASURING INSTRUMENTS
M1 Screw gauge 54
M2 Vernier Calipers 58
M3 Travelling Microscope 62
M4 Spectrometer 66








6

TORSIONAL PENDULUM










7

Expt. No.1 TORSIONAL PENDULUM

AIM:
To determine the moment of inertia of the given disc and hence to determine the rigidity modulus of
the material of the given suspension wire by torsional oscillations
APPARATUS REQUIRED:
Torsional pendulum, two equal masses, stop clock, screw gauge and meter scale

FORMULA:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
where
m ?mass of the cylinder placed on the disc (kg)
To ?period of the pendulum for a length of l without mass (s)
T1?period of the pendulum for the same length when mass m is placed at a distance d 1
from the center of the suspension wire (s)
T2?period of the pendulum for the same length when mass m is placed at a distance d 2
from the center of the suspension wire (s)
a ? radius of the suspension wire (m)




8

1. To determine the time period of the disc:
Length of the wire (l)= --------
2
10
?
? m
Position of the equal
masses
Time for 10 oscillations Time period
(one oscillation)
s
Trial-1
s
Trial-2
s
Mean
s
Without any masses T0
With masses at
d1 = x10
-2
m
T1
With masses at
d2 = x10
-2
m
T2

2. To determine the radius of the wire:
Least count =0 .01 mm. Zero Error ZE = --------- divisions
Zero Correction ZC = ---------- mm

Sl.No.
Pitch Scale
Reading
PSR
3
10
?
? m
Head Scale
Coincidence
HSC
div
Observed reading
OR = PSR + (HSCXLC)
3
10
?
? m
Correct reading
CR = OR ? ZC
3
10
?
? m




Mean = ----------------
3
10
?
? m



9

PROCEDURE:
Torsional pendulum is suspended from vertical chuck. The length of the suspension wire is measured
between the vertical chuck and the chuck attached to the uniform circular disc (i). The circular disc is twisted
slightly without masses on the disc. Now it executes torsional oscillations. Care is taken to see that the disc
oscillates without wobbling. Time taken for 20 oscillations is noted with the help of a stop clock. Two trials are
taken. The average of these two trial readings is calculated from which the period of oscillations is found out
as T0.
Two identical cylindrical masses each of mass m are symmetrically placed on the disc on either side
of the wire at a distance d from the center of the disc. As before the disc is gently twisted. Time taken for 20
oscillations is noted from which the period of oscillation is calculated as T1.
The cylindrical masses are placed at a distance d2 from the center and the experiment is repeated.
The mean time period of oscillations is calculated T2.
The diameter of the specimen wire is measured accurately with the help of the screw gauge, at
various places on the wire. The average diameter and hence the radius of the wire is calculated as r.
Moment of inertia and the rigidity modulus are determined by the substituting the value of m, T 0, T1, T2,
T3, and l in the formula.










10

CALCULATION:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2

Mass of cylindrical mass, m = ----------- ? 10
-3
kg
Closest distance of the mass from the centre of the suspension wire, d1 = ------------ ? 10
-2
m
Farthest distance of the mass from the centre of suspension wire, d2= ------------? 10
-2
m
Period of oscillation without mass, To = ------------- s
Period of oscillation with mass at d1, T1= ------------ s
Period of oscillation with mass at d2, T2 = ------------- s

Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
= --------------- kg m
2
= --------------- kg m
2

Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
Moment of inertia, I = ------------------ kg m
2
Length of the wire, l = ------------------- ? 10
-2
m
Time of oscillation, To = ------------------ s
Radius of the wire, a = ------------------- ? 10
-3
m
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
= ----------------------
Rigidity modulus, n = ------------------- Nm
-2
11









RESULT:
(i)
The moment of inertia of the given circular disc, I = --------------- kg m
2
(ii)
The rigidity modulus of the material of the given wire, n = -------------- Nm
-2




1. State Hooke?s law.
2. Define ?Rigidity modulus
3. Define ?Moment of inertia
4. What is meant by torsional oscillation?
5. What is period of oscillation?
6. What is meant by twisting couple?
7. Define ? Shearing stress
8. Define ? Shearing strain
9. What is the unit of rigidity modulus?
10. What are the applications of torsional pendulum?


Viva ? voce
12


Young?s Modulus ? Non Uniform Bending
To determine depression (y):
L.C =.001cm M = ___________
3
10
?
? kg

Sl.No

Load


3
10
?
?
k
g
Microscope reading
Mean

2
10
?
? m
Depression
y for M kg

2
10
?
? m
Loading Unloading
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
1 W
2 W+50
3 W+100
4 W+150
5 W+200
6 W+250

Mean (y) = ----------
2
10
?
? m





13

Expt. No.2 YOUNG?S MODULUS BY NON ? UNIFORM BENDING
AIM:
To determine the young?s modulus of the material of the given bar, by non-uniform bending method
APPARATUS REQUIRED:
Travelling microscope, wooden bar, knife- edge, weights hanger, slotted weight, vernier calipers,
screw gauge and pin
FORMULA:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Where,
g ? acceleration due to gravity (9.8 ms
-2
)
l ? length of the bar between two knife edges (m)
b ? breadth of the bar (m)
d ? thickness of the bar (m)
y ? depressiont in the scale reading due to the change of mass M (m)
PROCEDURE:
The given wooden bar, for which young?s modulus is to be determined, is paced symmetrically on the
two knife edges. The distance between the knife edges is measured as the length of the bar (l). It is adjusted
to be, say, 60 cm. the weight hanger is suspended at the centre of the bar. A pin is held vertically at the
centre of the bar with the help of wax.
The given bar is brought to elastic mood by loading and unloading the bar with slotted weights in steps
of 50 g. This is repeated for two or three times. With the hanger as dead load W, the microscope is focused on
to the tip of the pin. The tangential screw of the microscope is adjusted so that the image of the tip of the pin
just touches the horizontal cross wire of the eyepiece. The main scale reading and the vernier scale
coincidence corresponding to this position are noted.
14

To find the breadth using vernier calipers, b:
Least count = ---------- cm Zero error = --------- div.
= ---------- ?10
-2
m Zero correction = ?ZE ?LC= --------- ?10
-2
m
Sl. No.

MSR
x 10
-2
m

VSC
div.
Observed reading
OR = MSR+(VSC ? LC)
x 10
-2
m
Correct Reading
CR = OR ? ZC
x 10
-2
m
1.

2.

3.


Mean, b = ------------------------?10
-2
m
To find the thickness using screw gauge, d:
Least count = ---------- mm Zero error = --------- div.
= ---------- ?10
-3
m Zero correction =ZE ?LC= --------- ?10
-3
m
Sl. No.

PSR
x 10
-3
m

HSC
div.
Observed reading
OR = PSR+ (HSC ? LC)
x 10
-3
m
Correct Reading
CR = OR ? ZC
x 10
-3
m
1.

2.

3.


Mean, d = ---------------------------?10
-3
m
15


The experiment is repeated by adding weights in steps of 50 g and every time the microscope is
adjusted for coincidence. The corresponding readings are noted. The experiment is repeated by unloading the
weights in steps of 50 g and the corresponding readings are tabulated. From this table, the shift in the scale
reading, say y, for a change of mass M is found out.
The breadth of the bar is measured at various points with the help of vernier calipers. Similarly the
thickness of the bar is measured by screw gauge. Substituting the values of M, y, l, d, b and g in the formula,
the young?s modulus of the material of the given bar is calculated.

















16

CALCULATION:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Acceleration due to gravity, g = 9.8 ms
-2
Length of the bar between two knife edges, l = ------------ ?10
-2
m
Breadth of the bar, b = ----------- ?10
-2
m
Thickness of the bar, d = ----------- ?10
-3
m
y = -----------?10
-2
m
E =
???? ?? 2
4?? ?? 3
?? Nm
-2

= ---------------
Young?s modulus, E = ----------- Nm
-2












17








RESULT:
Young?s modulus of the material of the given bar, E = ---------- Nm
-2


1. Define ? Young?s modulus
2. What is meant by Non-uniform bending?
3. Define ? Stress and strain
4. State Hooke?s law.
5. Define ? Neutral axis
6. What is the SI unit of young?s modulus?
7. Define ? Elastic limit
8. Define ? Elasticity
9. What are the factors affecting elasticity?
10. Define ? Elastic fatigue

Viva ? voce
18


To find the wavelength of the laser beam, ?:
Distance between the screen and the grating, D = ------------?10
-2
m
Number of lines per meter length of the grating, N = --------------- Lines per meter
Sl. No.
Order of diffraction,
(m)
Reading of the diffracted image
(?10
-2
m)
?? ?? = ?????? ?1
(
?? ?? ?? )
(deg.)
? =
?????? ?? ?? ????
m

Left side
(xi)
Right side
(xr)
Mean
(xm)










Mean, ? = ---------------- m


19

Expt. No.3(a) WAVELENGTH OF LASER LIGHT AND PARTICLE SIZE


AIM:
(i) To determine the wavelength of the given laser light.
(ii) To determine size of the given particle.
APPARATUS REQUIRED:
Diode laser, grating, screen, given micro particles, scale and screen.
FORMULAE:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
(ii) Grain size or diameter of the grain, 2d =
?????? ?? ?? m
Where
?? ?? ?angle of diffraction (deg.)
M ?order of diffraction (No unit)
N ?number of lines per metre length of the grating (m
-3
)
n ? order of diffraction (no unit)
? ? wavelength of laser light used (m)
D ? distance between the glass plate and the screen (m)
?? ?? - distance between the central bright spot and the nth fringe (m)
PROCEDURE:
TO FIND THE WAVELENGTH OF THE GIVEN LASER LIGHT:
The laser source, grating and screen are placed properly as shown in figure. The diode laser is kept
horizontally and switched on. Extreme care should be taken to avoid direct exposure of laser light on eyes.
20











21

The grating is held normal to the laser beam by adjusting the grating in such a way that the reflected
laser beam from the grating coincides with incident laser beam. Now the diffracted laser spots of various
orders can be seen on the screen, placed on the other side of the grating.

The distance of the different orders on either side of the central spot are measured as x randxi and are
tabulated.The mean value of xrandxiare calculated as xm for the m
th
order diffracted light. The distance
between the grating and the screen is measured as D. Hence, the angle of diffraction for the m
th
order,
?? ?? = ?????? ?1
(
?? ?? ?? )
The experiment is repeated for different orders and the readings are tabulated. From the table, ? for
each order is calculated. Substituting the value of ?, the corresponding order of diffraction and the number of
lines per meter length of the grating, the wavelength is calculated.

TO FIND THE SIZE OF THE GIVEN MICRO PARTICLE:

The lycopodium powder having fine micro particles of nearly same size is sprinkled on a glass plate.
This glass plate is kept between laser source and screen.
Now the particles present in the glass plate diffract laser beam from the source. By adjusting the
distance between the glass plate and the screen, a circular fringe pattern is obtained on the screen with
different orders of fingers. Now distance between the screen and the glass plate (D) is measured.
The distance of the first order and the second order fringe from the centre of spot are also measured.
Using the formula, the particle size is found out. The experiment is repeated for different D values.
22

To find the size of the particle:

CALCULATION:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
Number of lines per metre in the grating, N = ------------ lines per metre.
First order, m1; ?? 1
= ------------
Wavelength, ? =
?????? ?? 1
????
= ------------
Second order, m2; ?? 2
= ------------
Wavelength, ? =
?????? ?? 2
????
= ------------
Third order, m3; ?? 3
= ------------
Wavelength, ? =
?????? ?? 3
????
= ------------
Fourth order, m4; ?? 4
= ------------
Wavelength, ? =
?????? ?? 4
????
= -------------
Fifth order, m5; ?? 5
= ------------

Sl.No



Distance between
screen and glass
plate(D)
2
10
?
? m
Order of
diffraction
(n)
Distance between the
central bright spot and n
th

fringe (xn )
2
10
?
? m
Particle size
2
n
nD
d
x
?
?
m






23

Wavelength, ? =
?????? ?? 4
????
= ------------
Mean wavelength of the given laser light, ? = -------------- m
(ii) Grain size or diameter of the grain. 2d =
?????? ?? ??
Order of differaction, n = --------------
Wavelength of laser light used, ? = ------------- m
Distance between glass plate and the screen, D = ------------ m
Distance between central bright spot and the n
th
fringe,?? ?? = ------------ m
2d =
?????? ?? ??
=
= ------------ m








RESULT:
(i) Wavelength of the laser beam, ? = -------------- m
(ii) Average size of the particle = --------------- m

FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
2


PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science and fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems and use this knowledge to acquire
higher education.
2. Core competence
To train the students in Engineering Physics so as to apply their knowledge and training to compare,
and to analyze various engineering industrial problems for finding solutions.
3. Breadth
To provide relevant training and experience to bridge the gap between theoretical learning and
practice that enables them to find solutions for the real time problems in industry and to design products.
4. Professionalism
To inculcate professional and effective communication skills, leadership qualities and team spirit for
the students to make them multi-faceted personalities and develop their ability to relate engineering issues
to broader social context.
5. Lifelong learning/ethics
To demonstrate and practice ethical and professional responsibilities in the industry and society by
and large, through commitment and lifelong learning needed for successful professional career.





3


PROGRAMME OUTCOMES (POs)

a) To demonstrate and apply knowledge of Mathematics, Science and Engineering fundamentals in
Engineering physics
b) To determine the Moment of Inertia of given disc and Rigidity modulus of the given wire using
Torsional Pendulum
c) To determine Young?s modulus of a given bar using Non-Uniform bending
d) To utilize laser source and grating to estimate the wave length, particle size of given powder and
Numerical Aperture & acceptance angle of given optical fiber
e) To find the Thermal conductivity of a bad conductor using Lee?s Disc method
f) To Measure the velocity of ultrasonic wave in a liquid and compressibility of the liquid usingultrasonic
Interferometer
g) To determine the wavelength of Hg source using grating and spectrometer
h) To find the thickness of a thin wire using Air- wedge method
i) To participate and succeed in competitive exams and visualize and work on laboratory and
multidisciplinary tasks











4


BS 8161 ? PHYSICSLABORATORY
(Common to all branches of B.E. / B.TechProgrammes)
SYLLABUS


To introduce different experiments to test basic understanding of physics concepts applied in optics, thermal
physics, properties of matter and liquids.

LIST OF EXPERIMENTS: PHYSICS LABORATORY(Any 5 Experiments)
1. Determination of Rigidity modulus ? Torsion pendulum
2. Determination of Young? s modulus by Non uniform bending method
3. (a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
4. Determination of thermal conductivity of a bad conductor ? Lee?s Disc method.
5. Determination of velocity of sound and compressibility of liquid ? Ultrasonic interferometer
6. Determination of wavelength of mercury spectrum ? spectrometer grating
7. Determination of band gap of a semiconductor
8. Determination of thickness of a thin wire ? Air wedge method




Completion of the course, the students will be able to: apply physics principles of optics and thermal physics
to evaluate engineering properties of materials.


COURSE OUTCOMES
COURSE OBJECTIVES
5

BS 8161 ? PHYSICS LABORATORY
CONTENTS

Sl.No. Name of the Experiment (any 5 experiments)
Page
No.
1.
Determination of Rigidity modulus ? Torsion pendulum
6
2.
Determination of Young ?s modulus by Non uniform bending method
12
3.
(a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
18
4.
Determination of thermal conductivity of a bad conductor ? Lee ?s Disc method.
28
5.
Determination of velocity of sound and compressibility of liquid ? Ultrasonic
interferometer
37
6.
Determination of wavelength of mercury spectrum ? spectrometer grating
42
7.
Determination of thickness of a thin wire ? Air wedge method
48
MEASURING INSTRUMENTS
M1 Screw gauge 54
M2 Vernier Calipers 58
M3 Travelling Microscope 62
M4 Spectrometer 66








6

TORSIONAL PENDULUM










7

Expt. No.1 TORSIONAL PENDULUM

AIM:
To determine the moment of inertia of the given disc and hence to determine the rigidity modulus of
the material of the given suspension wire by torsional oscillations
APPARATUS REQUIRED:
Torsional pendulum, two equal masses, stop clock, screw gauge and meter scale

FORMULA:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
where
m ?mass of the cylinder placed on the disc (kg)
To ?period of the pendulum for a length of l without mass (s)
T1?period of the pendulum for the same length when mass m is placed at a distance d 1
from the center of the suspension wire (s)
T2?period of the pendulum for the same length when mass m is placed at a distance d 2
from the center of the suspension wire (s)
a ? radius of the suspension wire (m)




8

1. To determine the time period of the disc:
Length of the wire (l)= --------
2
10
?
? m
Position of the equal
masses
Time for 10 oscillations Time period
(one oscillation)
s
Trial-1
s
Trial-2
s
Mean
s
Without any masses T0
With masses at
d1 = x10
-2
m
T1
With masses at
d2 = x10
-2
m
T2

2. To determine the radius of the wire:
Least count =0 .01 mm. Zero Error ZE = --------- divisions
Zero Correction ZC = ---------- mm

Sl.No.
Pitch Scale
Reading
PSR
3
10
?
? m
Head Scale
Coincidence
HSC
div
Observed reading
OR = PSR + (HSCXLC)
3
10
?
? m
Correct reading
CR = OR ? ZC
3
10
?
? m




Mean = ----------------
3
10
?
? m



9

PROCEDURE:
Torsional pendulum is suspended from vertical chuck. The length of the suspension wire is measured
between the vertical chuck and the chuck attached to the uniform circular disc (i). The circular disc is twisted
slightly without masses on the disc. Now it executes torsional oscillations. Care is taken to see that the disc
oscillates without wobbling. Time taken for 20 oscillations is noted with the help of a stop clock. Two trials are
taken. The average of these two trial readings is calculated from which the period of oscillations is found out
as T0.
Two identical cylindrical masses each of mass m are symmetrically placed on the disc on either side
of the wire at a distance d from the center of the disc. As before the disc is gently twisted. Time taken for 20
oscillations is noted from which the period of oscillation is calculated as T1.
The cylindrical masses are placed at a distance d2 from the center and the experiment is repeated.
The mean time period of oscillations is calculated T2.
The diameter of the specimen wire is measured accurately with the help of the screw gauge, at
various places on the wire. The average diameter and hence the radius of the wire is calculated as r.
Moment of inertia and the rigidity modulus are determined by the substituting the value of m, T 0, T1, T2,
T3, and l in the formula.










10

CALCULATION:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2

Mass of cylindrical mass, m = ----------- ? 10
-3
kg
Closest distance of the mass from the centre of the suspension wire, d1 = ------------ ? 10
-2
m
Farthest distance of the mass from the centre of suspension wire, d2= ------------? 10
-2
m
Period of oscillation without mass, To = ------------- s
Period of oscillation with mass at d1, T1= ------------ s
Period of oscillation with mass at d2, T2 = ------------- s

Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
= --------------- kg m
2
= --------------- kg m
2

Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
Moment of inertia, I = ------------------ kg m
2
Length of the wire, l = ------------------- ? 10
-2
m
Time of oscillation, To = ------------------ s
Radius of the wire, a = ------------------- ? 10
-3
m
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
= ----------------------
Rigidity modulus, n = ------------------- Nm
-2
11









RESULT:
(i)
The moment of inertia of the given circular disc, I = --------------- kg m
2
(ii)
The rigidity modulus of the material of the given wire, n = -------------- Nm
-2




1. State Hooke?s law.
2. Define ?Rigidity modulus
3. Define ?Moment of inertia
4. What is meant by torsional oscillation?
5. What is period of oscillation?
6. What is meant by twisting couple?
7. Define ? Shearing stress
8. Define ? Shearing strain
9. What is the unit of rigidity modulus?
10. What are the applications of torsional pendulum?


Viva ? voce
12


Young?s Modulus ? Non Uniform Bending
To determine depression (y):
L.C =.001cm M = ___________
3
10
?
? kg

Sl.No

Load


3
10
?
?
k
g
Microscope reading
Mean

2
10
?
? m
Depression
y for M kg

2
10
?
? m
Loading Unloading
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
1 W
2 W+50
3 W+100
4 W+150
5 W+200
6 W+250

Mean (y) = ----------
2
10
?
? m





13

Expt. No.2 YOUNG?S MODULUS BY NON ? UNIFORM BENDING
AIM:
To determine the young?s modulus of the material of the given bar, by non-uniform bending method
APPARATUS REQUIRED:
Travelling microscope, wooden bar, knife- edge, weights hanger, slotted weight, vernier calipers,
screw gauge and pin
FORMULA:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Where,
g ? acceleration due to gravity (9.8 ms
-2
)
l ? length of the bar between two knife edges (m)
b ? breadth of the bar (m)
d ? thickness of the bar (m)
y ? depressiont in the scale reading due to the change of mass M (m)
PROCEDURE:
The given wooden bar, for which young?s modulus is to be determined, is paced symmetrically on the
two knife edges. The distance between the knife edges is measured as the length of the bar (l). It is adjusted
to be, say, 60 cm. the weight hanger is suspended at the centre of the bar. A pin is held vertically at the
centre of the bar with the help of wax.
The given bar is brought to elastic mood by loading and unloading the bar with slotted weights in steps
of 50 g. This is repeated for two or three times. With the hanger as dead load W, the microscope is focused on
to the tip of the pin. The tangential screw of the microscope is adjusted so that the image of the tip of the pin
just touches the horizontal cross wire of the eyepiece. The main scale reading and the vernier scale
coincidence corresponding to this position are noted.
14

To find the breadth using vernier calipers, b:
Least count = ---------- cm Zero error = --------- div.
= ---------- ?10
-2
m Zero correction = ?ZE ?LC= --------- ?10
-2
m
Sl. No.

MSR
x 10
-2
m

VSC
div.
Observed reading
OR = MSR+(VSC ? LC)
x 10
-2
m
Correct Reading
CR = OR ? ZC
x 10
-2
m
1.

2.

3.


Mean, b = ------------------------?10
-2
m
To find the thickness using screw gauge, d:
Least count = ---------- mm Zero error = --------- div.
= ---------- ?10
-3
m Zero correction =ZE ?LC= --------- ?10
-3
m
Sl. No.

PSR
x 10
-3
m

HSC
div.
Observed reading
OR = PSR+ (HSC ? LC)
x 10
-3
m
Correct Reading
CR = OR ? ZC
x 10
-3
m
1.

2.

3.


Mean, d = ---------------------------?10
-3
m
15


The experiment is repeated by adding weights in steps of 50 g and every time the microscope is
adjusted for coincidence. The corresponding readings are noted. The experiment is repeated by unloading the
weights in steps of 50 g and the corresponding readings are tabulated. From this table, the shift in the scale
reading, say y, for a change of mass M is found out.
The breadth of the bar is measured at various points with the help of vernier calipers. Similarly the
thickness of the bar is measured by screw gauge. Substituting the values of M, y, l, d, b and g in the formula,
the young?s modulus of the material of the given bar is calculated.

















16

CALCULATION:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Acceleration due to gravity, g = 9.8 ms
-2
Length of the bar between two knife edges, l = ------------ ?10
-2
m
Breadth of the bar, b = ----------- ?10
-2
m
Thickness of the bar, d = ----------- ?10
-3
m
y = -----------?10
-2
m
E =
???? ?? 2
4?? ?? 3
?? Nm
-2

= ---------------
Young?s modulus, E = ----------- Nm
-2












17








RESULT:
Young?s modulus of the material of the given bar, E = ---------- Nm
-2


1. Define ? Young?s modulus
2. What is meant by Non-uniform bending?
3. Define ? Stress and strain
4. State Hooke?s law.
5. Define ? Neutral axis
6. What is the SI unit of young?s modulus?
7. Define ? Elastic limit
8. Define ? Elasticity
9. What are the factors affecting elasticity?
10. Define ? Elastic fatigue

Viva ? voce
18


To find the wavelength of the laser beam, ?:
Distance between the screen and the grating, D = ------------?10
-2
m
Number of lines per meter length of the grating, N = --------------- Lines per meter
Sl. No.
Order of diffraction,
(m)
Reading of the diffracted image
(?10
-2
m)
?? ?? = ?????? ?1
(
?? ?? ?? )
(deg.)
? =
?????? ?? ?? ????
m

Left side
(xi)
Right side
(xr)
Mean
(xm)










Mean, ? = ---------------- m


19

Expt. No.3(a) WAVELENGTH OF LASER LIGHT AND PARTICLE SIZE


AIM:
(i) To determine the wavelength of the given laser light.
(ii) To determine size of the given particle.
APPARATUS REQUIRED:
Diode laser, grating, screen, given micro particles, scale and screen.
FORMULAE:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
(ii) Grain size or diameter of the grain, 2d =
?????? ?? ?? m
Where
?? ?? ?angle of diffraction (deg.)
M ?order of diffraction (No unit)
N ?number of lines per metre length of the grating (m
-3
)
n ? order of diffraction (no unit)
? ? wavelength of laser light used (m)
D ? distance between the glass plate and the screen (m)
?? ?? - distance between the central bright spot and the nth fringe (m)
PROCEDURE:
TO FIND THE WAVELENGTH OF THE GIVEN LASER LIGHT:
The laser source, grating and screen are placed properly as shown in figure. The diode laser is kept
horizontally and switched on. Extreme care should be taken to avoid direct exposure of laser light on eyes.
20











21

The grating is held normal to the laser beam by adjusting the grating in such a way that the reflected
laser beam from the grating coincides with incident laser beam. Now the diffracted laser spots of various
orders can be seen on the screen, placed on the other side of the grating.

The distance of the different orders on either side of the central spot are measured as x randxi and are
tabulated.The mean value of xrandxiare calculated as xm for the m
th
order diffracted light. The distance
between the grating and the screen is measured as D. Hence, the angle of diffraction for the m
th
order,
?? ?? = ?????? ?1
(
?? ?? ?? )
The experiment is repeated for different orders and the readings are tabulated. From the table, ? for
each order is calculated. Substituting the value of ?, the corresponding order of diffraction and the number of
lines per meter length of the grating, the wavelength is calculated.

TO FIND THE SIZE OF THE GIVEN MICRO PARTICLE:

The lycopodium powder having fine micro particles of nearly same size is sprinkled on a glass plate.
This glass plate is kept between laser source and screen.
Now the particles present in the glass plate diffract laser beam from the source. By adjusting the
distance between the glass plate and the screen, a circular fringe pattern is obtained on the screen with
different orders of fingers. Now distance between the screen and the glass plate (D) is measured.
The distance of the first order and the second order fringe from the centre of spot are also measured.
Using the formula, the particle size is found out. The experiment is repeated for different D values.
22

To find the size of the particle:

CALCULATION:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
Number of lines per metre in the grating, N = ------------ lines per metre.
First order, m1; ?? 1
= ------------
Wavelength, ? =
?????? ?? 1
????
= ------------
Second order, m2; ?? 2
= ------------
Wavelength, ? =
?????? ?? 2
????
= ------------
Third order, m3; ?? 3
= ------------
Wavelength, ? =
?????? ?? 3
????
= ------------
Fourth order, m4; ?? 4
= ------------
Wavelength, ? =
?????? ?? 4
????
= -------------
Fifth order, m5; ?? 5
= ------------

Sl.No



Distance between
screen and glass
plate(D)
2
10
?
? m
Order of
diffraction
(n)
Distance between the
central bright spot and n
th

fringe (xn )
2
10
?
? m
Particle size
2
n
nD
d
x
?
?
m






23

Wavelength, ? =
?????? ?? 4
????
= ------------
Mean wavelength of the given laser light, ? = -------------- m
(ii) Grain size or diameter of the grain. 2d =
?????? ?? ??
Order of differaction, n = --------------
Wavelength of laser light used, ? = ------------- m
Distance between glass plate and the screen, D = ------------ m
Distance between central bright spot and the n
th
fringe,?? ?? = ------------ m
2d =
?????? ?? ??
=
= ------------ m








RESULT:
(i) Wavelength of the laser beam, ? = -------------- m
(ii) Average size of the particle = --------------- m

24


Optical fiber

To find numerical aperture, NA:

Sl. No.
Diameter of the circular patch
D(m)
Distance between the tip of the
fiber and the screen X (m)
NA =
?? (4?? 2
+?? 2
)
1
2





Mean NA =
Therefore, the acceptance angle, ? = Sin
-1
(NA) = -------------------
= -------------------


FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
2


PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science and fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems and use this knowledge to acquire
higher education.
2. Core competence
To train the students in Engineering Physics so as to apply their knowledge and training to compare,
and to analyze various engineering industrial problems for finding solutions.
3. Breadth
To provide relevant training and experience to bridge the gap between theoretical learning and
practice that enables them to find solutions for the real time problems in industry and to design products.
4. Professionalism
To inculcate professional and effective communication skills, leadership qualities and team spirit for
the students to make them multi-faceted personalities and develop their ability to relate engineering issues
to broader social context.
5. Lifelong learning/ethics
To demonstrate and practice ethical and professional responsibilities in the industry and society by
and large, through commitment and lifelong learning needed for successful professional career.





3


PROGRAMME OUTCOMES (POs)

a) To demonstrate and apply knowledge of Mathematics, Science and Engineering fundamentals in
Engineering physics
b) To determine the Moment of Inertia of given disc and Rigidity modulus of the given wire using
Torsional Pendulum
c) To determine Young?s modulus of a given bar using Non-Uniform bending
d) To utilize laser source and grating to estimate the wave length, particle size of given powder and
Numerical Aperture & acceptance angle of given optical fiber
e) To find the Thermal conductivity of a bad conductor using Lee?s Disc method
f) To Measure the velocity of ultrasonic wave in a liquid and compressibility of the liquid usingultrasonic
Interferometer
g) To determine the wavelength of Hg source using grating and spectrometer
h) To find the thickness of a thin wire using Air- wedge method
i) To participate and succeed in competitive exams and visualize and work on laboratory and
multidisciplinary tasks











4


BS 8161 ? PHYSICSLABORATORY
(Common to all branches of B.E. / B.TechProgrammes)
SYLLABUS


To introduce different experiments to test basic understanding of physics concepts applied in optics, thermal
physics, properties of matter and liquids.

LIST OF EXPERIMENTS: PHYSICS LABORATORY(Any 5 Experiments)
1. Determination of Rigidity modulus ? Torsion pendulum
2. Determination of Young? s modulus by Non uniform bending method
3. (a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
4. Determination of thermal conductivity of a bad conductor ? Lee?s Disc method.
5. Determination of velocity of sound and compressibility of liquid ? Ultrasonic interferometer
6. Determination of wavelength of mercury spectrum ? spectrometer grating
7. Determination of band gap of a semiconductor
8. Determination of thickness of a thin wire ? Air wedge method




Completion of the course, the students will be able to: apply physics principles of optics and thermal physics
to evaluate engineering properties of materials.


COURSE OUTCOMES
COURSE OBJECTIVES
5

BS 8161 ? PHYSICS LABORATORY
CONTENTS

Sl.No. Name of the Experiment (any 5 experiments)
Page
No.
1.
Determination of Rigidity modulus ? Torsion pendulum
6
2.
Determination of Young ?s modulus by Non uniform bending method
12
3.
(a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
18
4.
Determination of thermal conductivity of a bad conductor ? Lee ?s Disc method.
28
5.
Determination of velocity of sound and compressibility of liquid ? Ultrasonic
interferometer
37
6.
Determination of wavelength of mercury spectrum ? spectrometer grating
42
7.
Determination of thickness of a thin wire ? Air wedge method
48
MEASURING INSTRUMENTS
M1 Screw gauge 54
M2 Vernier Calipers 58
M3 Travelling Microscope 62
M4 Spectrometer 66








6

TORSIONAL PENDULUM










7

Expt. No.1 TORSIONAL PENDULUM

AIM:
To determine the moment of inertia of the given disc and hence to determine the rigidity modulus of
the material of the given suspension wire by torsional oscillations
APPARATUS REQUIRED:
Torsional pendulum, two equal masses, stop clock, screw gauge and meter scale

FORMULA:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
where
m ?mass of the cylinder placed on the disc (kg)
To ?period of the pendulum for a length of l without mass (s)
T1?period of the pendulum for the same length when mass m is placed at a distance d 1
from the center of the suspension wire (s)
T2?period of the pendulum for the same length when mass m is placed at a distance d 2
from the center of the suspension wire (s)
a ? radius of the suspension wire (m)




8

1. To determine the time period of the disc:
Length of the wire (l)= --------
2
10
?
? m
Position of the equal
masses
Time for 10 oscillations Time period
(one oscillation)
s
Trial-1
s
Trial-2
s
Mean
s
Without any masses T0
With masses at
d1 = x10
-2
m
T1
With masses at
d2 = x10
-2
m
T2

2. To determine the radius of the wire:
Least count =0 .01 mm. Zero Error ZE = --------- divisions
Zero Correction ZC = ---------- mm

Sl.No.
Pitch Scale
Reading
PSR
3
10
?
? m
Head Scale
Coincidence
HSC
div
Observed reading
OR = PSR + (HSCXLC)
3
10
?
? m
Correct reading
CR = OR ? ZC
3
10
?
? m




Mean = ----------------
3
10
?
? m



9

PROCEDURE:
Torsional pendulum is suspended from vertical chuck. The length of the suspension wire is measured
between the vertical chuck and the chuck attached to the uniform circular disc (i). The circular disc is twisted
slightly without masses on the disc. Now it executes torsional oscillations. Care is taken to see that the disc
oscillates without wobbling. Time taken for 20 oscillations is noted with the help of a stop clock. Two trials are
taken. The average of these two trial readings is calculated from which the period of oscillations is found out
as T0.
Two identical cylindrical masses each of mass m are symmetrically placed on the disc on either side
of the wire at a distance d from the center of the disc. As before the disc is gently twisted. Time taken for 20
oscillations is noted from which the period of oscillation is calculated as T1.
The cylindrical masses are placed at a distance d2 from the center and the experiment is repeated.
The mean time period of oscillations is calculated T2.
The diameter of the specimen wire is measured accurately with the help of the screw gauge, at
various places on the wire. The average diameter and hence the radius of the wire is calculated as r.
Moment of inertia and the rigidity modulus are determined by the substituting the value of m, T 0, T1, T2,
T3, and l in the formula.










10

CALCULATION:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2

Mass of cylindrical mass, m = ----------- ? 10
-3
kg
Closest distance of the mass from the centre of the suspension wire, d1 = ------------ ? 10
-2
m
Farthest distance of the mass from the centre of suspension wire, d2= ------------? 10
-2
m
Period of oscillation without mass, To = ------------- s
Period of oscillation with mass at d1, T1= ------------ s
Period of oscillation with mass at d2, T2 = ------------- s

Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
= --------------- kg m
2
= --------------- kg m
2

Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
Moment of inertia, I = ------------------ kg m
2
Length of the wire, l = ------------------- ? 10
-2
m
Time of oscillation, To = ------------------ s
Radius of the wire, a = ------------------- ? 10
-3
m
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
= ----------------------
Rigidity modulus, n = ------------------- Nm
-2
11









RESULT:
(i)
The moment of inertia of the given circular disc, I = --------------- kg m
2
(ii)
The rigidity modulus of the material of the given wire, n = -------------- Nm
-2




1. State Hooke?s law.
2. Define ?Rigidity modulus
3. Define ?Moment of inertia
4. What is meant by torsional oscillation?
5. What is period of oscillation?
6. What is meant by twisting couple?
7. Define ? Shearing stress
8. Define ? Shearing strain
9. What is the unit of rigidity modulus?
10. What are the applications of torsional pendulum?


Viva ? voce
12


Young?s Modulus ? Non Uniform Bending
To determine depression (y):
L.C =.001cm M = ___________
3
10
?
? kg

Sl.No

Load


3
10
?
?
k
g
Microscope reading
Mean

2
10
?
? m
Depression
y for M kg

2
10
?
? m
Loading Unloading
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
1 W
2 W+50
3 W+100
4 W+150
5 W+200
6 W+250

Mean (y) = ----------
2
10
?
? m





13

Expt. No.2 YOUNG?S MODULUS BY NON ? UNIFORM BENDING
AIM:
To determine the young?s modulus of the material of the given bar, by non-uniform bending method
APPARATUS REQUIRED:
Travelling microscope, wooden bar, knife- edge, weights hanger, slotted weight, vernier calipers,
screw gauge and pin
FORMULA:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Where,
g ? acceleration due to gravity (9.8 ms
-2
)
l ? length of the bar between two knife edges (m)
b ? breadth of the bar (m)
d ? thickness of the bar (m)
y ? depressiont in the scale reading due to the change of mass M (m)
PROCEDURE:
The given wooden bar, for which young?s modulus is to be determined, is paced symmetrically on the
two knife edges. The distance between the knife edges is measured as the length of the bar (l). It is adjusted
to be, say, 60 cm. the weight hanger is suspended at the centre of the bar. A pin is held vertically at the
centre of the bar with the help of wax.
The given bar is brought to elastic mood by loading and unloading the bar with slotted weights in steps
of 50 g. This is repeated for two or three times. With the hanger as dead load W, the microscope is focused on
to the tip of the pin. The tangential screw of the microscope is adjusted so that the image of the tip of the pin
just touches the horizontal cross wire of the eyepiece. The main scale reading and the vernier scale
coincidence corresponding to this position are noted.
14

To find the breadth using vernier calipers, b:
Least count = ---------- cm Zero error = --------- div.
= ---------- ?10
-2
m Zero correction = ?ZE ?LC= --------- ?10
-2
m
Sl. No.

MSR
x 10
-2
m

VSC
div.
Observed reading
OR = MSR+(VSC ? LC)
x 10
-2
m
Correct Reading
CR = OR ? ZC
x 10
-2
m
1.

2.

3.


Mean, b = ------------------------?10
-2
m
To find the thickness using screw gauge, d:
Least count = ---------- mm Zero error = --------- div.
= ---------- ?10
-3
m Zero correction =ZE ?LC= --------- ?10
-3
m
Sl. No.

PSR
x 10
-3
m

HSC
div.
Observed reading
OR = PSR+ (HSC ? LC)
x 10
-3
m
Correct Reading
CR = OR ? ZC
x 10
-3
m
1.

2.

3.


Mean, d = ---------------------------?10
-3
m
15


The experiment is repeated by adding weights in steps of 50 g and every time the microscope is
adjusted for coincidence. The corresponding readings are noted. The experiment is repeated by unloading the
weights in steps of 50 g and the corresponding readings are tabulated. From this table, the shift in the scale
reading, say y, for a change of mass M is found out.
The breadth of the bar is measured at various points with the help of vernier calipers. Similarly the
thickness of the bar is measured by screw gauge. Substituting the values of M, y, l, d, b and g in the formula,
the young?s modulus of the material of the given bar is calculated.

















16

CALCULATION:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Acceleration due to gravity, g = 9.8 ms
-2
Length of the bar between two knife edges, l = ------------ ?10
-2
m
Breadth of the bar, b = ----------- ?10
-2
m
Thickness of the bar, d = ----------- ?10
-3
m
y = -----------?10
-2
m
E =
???? ?? 2
4?? ?? 3
?? Nm
-2

= ---------------
Young?s modulus, E = ----------- Nm
-2












17








RESULT:
Young?s modulus of the material of the given bar, E = ---------- Nm
-2


1. Define ? Young?s modulus
2. What is meant by Non-uniform bending?
3. Define ? Stress and strain
4. State Hooke?s law.
5. Define ? Neutral axis
6. What is the SI unit of young?s modulus?
7. Define ? Elastic limit
8. Define ? Elasticity
9. What are the factors affecting elasticity?
10. Define ? Elastic fatigue

Viva ? voce
18


To find the wavelength of the laser beam, ?:
Distance between the screen and the grating, D = ------------?10
-2
m
Number of lines per meter length of the grating, N = --------------- Lines per meter
Sl. No.
Order of diffraction,
(m)
Reading of the diffracted image
(?10
-2
m)
?? ?? = ?????? ?1
(
?? ?? ?? )
(deg.)
? =
?????? ?? ?? ????
m

Left side
(xi)
Right side
(xr)
Mean
(xm)










Mean, ? = ---------------- m


19

Expt. No.3(a) WAVELENGTH OF LASER LIGHT AND PARTICLE SIZE


AIM:
(i) To determine the wavelength of the given laser light.
(ii) To determine size of the given particle.
APPARATUS REQUIRED:
Diode laser, grating, screen, given micro particles, scale and screen.
FORMULAE:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
(ii) Grain size or diameter of the grain, 2d =
?????? ?? ?? m
Where
?? ?? ?angle of diffraction (deg.)
M ?order of diffraction (No unit)
N ?number of lines per metre length of the grating (m
-3
)
n ? order of diffraction (no unit)
? ? wavelength of laser light used (m)
D ? distance between the glass plate and the screen (m)
?? ?? - distance between the central bright spot and the nth fringe (m)
PROCEDURE:
TO FIND THE WAVELENGTH OF THE GIVEN LASER LIGHT:
The laser source, grating and screen are placed properly as shown in figure. The diode laser is kept
horizontally and switched on. Extreme care should be taken to avoid direct exposure of laser light on eyes.
20











21

The grating is held normal to the laser beam by adjusting the grating in such a way that the reflected
laser beam from the grating coincides with incident laser beam. Now the diffracted laser spots of various
orders can be seen on the screen, placed on the other side of the grating.

The distance of the different orders on either side of the central spot are measured as x randxi and are
tabulated.The mean value of xrandxiare calculated as xm for the m
th
order diffracted light. The distance
between the grating and the screen is measured as D. Hence, the angle of diffraction for the m
th
order,
?? ?? = ?????? ?1
(
?? ?? ?? )
The experiment is repeated for different orders and the readings are tabulated. From the table, ? for
each order is calculated. Substituting the value of ?, the corresponding order of diffraction and the number of
lines per meter length of the grating, the wavelength is calculated.

TO FIND THE SIZE OF THE GIVEN MICRO PARTICLE:

The lycopodium powder having fine micro particles of nearly same size is sprinkled on a glass plate.
This glass plate is kept between laser source and screen.
Now the particles present in the glass plate diffract laser beam from the source. By adjusting the
distance between the glass plate and the screen, a circular fringe pattern is obtained on the screen with
different orders of fingers. Now distance between the screen and the glass plate (D) is measured.
The distance of the first order and the second order fringe from the centre of spot are also measured.
Using the formula, the particle size is found out. The experiment is repeated for different D values.
22

To find the size of the particle:

CALCULATION:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
Number of lines per metre in the grating, N = ------------ lines per metre.
First order, m1; ?? 1
= ------------
Wavelength, ? =
?????? ?? 1
????
= ------------
Second order, m2; ?? 2
= ------------
Wavelength, ? =
?????? ?? 2
????
= ------------
Third order, m3; ?? 3
= ------------
Wavelength, ? =
?????? ?? 3
????
= ------------
Fourth order, m4; ?? 4
= ------------
Wavelength, ? =
?????? ?? 4
????
= -------------
Fifth order, m5; ?? 5
= ------------

Sl.No



Distance between
screen and glass
plate(D)
2
10
?
? m
Order of
diffraction
(n)
Distance between the
central bright spot and n
th

fringe (xn )
2
10
?
? m
Particle size
2
n
nD
d
x
?
?
m






23

Wavelength, ? =
?????? ?? 4
????
= ------------
Mean wavelength of the given laser light, ? = -------------- m
(ii) Grain size or diameter of the grain. 2d =
?????? ?? ??
Order of differaction, n = --------------
Wavelength of laser light used, ? = ------------- m
Distance between glass plate and the screen, D = ------------ m
Distance between central bright spot and the n
th
fringe,?? ?? = ------------ m
2d =
?????? ?? ??
=
= ------------ m








RESULT:
(i) Wavelength of the laser beam, ? = -------------- m
(ii) Average size of the particle = --------------- m

24


Optical fiber

To find numerical aperture, NA:

Sl. No.
Diameter of the circular patch
D(m)
Distance between the tip of the
fiber and the screen X (m)
NA =
?? (4?? 2
+?? 2
)
1
2





Mean NA =
Therefore, the acceptance angle, ? = Sin
-1
(NA) = -------------------
= -------------------


25

Expt. No.3(b) NUMERICAL APERTURE AND ACCEPTANCE ANGLE
AIM:
To measure the numerical aperture and the acceptance angle of the given fiber cable
APPARATUS REQUIRED:
Optical fiber cable with source, NA jig and in-line adaptor
FORMULA:
The numerical aperture, NA =
?? (4?? 2
+?? 2
)
1
2

Acceptance angle, ? = Sin
-1
(NA)
where,
D ? diameter of the circular patch (m)
X ? distance between the tip of the fiber and the screen (m)
PROCEDURE:
One end of the one metre fiber cable is connected to the laser light source and the other end
to the NA jig as shown in figure. The AC main is plugged in and the laser light is adjusted so that it appears at
the end of the fiber on the NA jig, the intensity knob is adjusted to get maximum intensity.
The white screen with the four concentric circles (10 mm, 20 mm, 30 mm and 40 mm diameter) is held
vertically at a suitable distance to make the red spot from the emitting fiber coincides with the 10 mm circle,
the diameter (D) of the spot is noted. The distance (X) of the screen from the fiber end is recorded.
The procedure is repeated for 20 mm, 30 mm, 40 mm diameter circles and the readings are tabulated.




FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
2


PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science and fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems and use this knowledge to acquire
higher education.
2. Core competence
To train the students in Engineering Physics so as to apply their knowledge and training to compare,
and to analyze various engineering industrial problems for finding solutions.
3. Breadth
To provide relevant training and experience to bridge the gap between theoretical learning and
practice that enables them to find solutions for the real time problems in industry and to design products.
4. Professionalism
To inculcate professional and effective communication skills, leadership qualities and team spirit for
the students to make them multi-faceted personalities and develop their ability to relate engineering issues
to broader social context.
5. Lifelong learning/ethics
To demonstrate and practice ethical and professional responsibilities in the industry and society by
and large, through commitment and lifelong learning needed for successful professional career.





3


PROGRAMME OUTCOMES (POs)

a) To demonstrate and apply knowledge of Mathematics, Science and Engineering fundamentals in
Engineering physics
b) To determine the Moment of Inertia of given disc and Rigidity modulus of the given wire using
Torsional Pendulum
c) To determine Young?s modulus of a given bar using Non-Uniform bending
d) To utilize laser source and grating to estimate the wave length, particle size of given powder and
Numerical Aperture & acceptance angle of given optical fiber
e) To find the Thermal conductivity of a bad conductor using Lee?s Disc method
f) To Measure the velocity of ultrasonic wave in a liquid and compressibility of the liquid usingultrasonic
Interferometer
g) To determine the wavelength of Hg source using grating and spectrometer
h) To find the thickness of a thin wire using Air- wedge method
i) To participate and succeed in competitive exams and visualize and work on laboratory and
multidisciplinary tasks











4


BS 8161 ? PHYSICSLABORATORY
(Common to all branches of B.E. / B.TechProgrammes)
SYLLABUS


To introduce different experiments to test basic understanding of physics concepts applied in optics, thermal
physics, properties of matter and liquids.

LIST OF EXPERIMENTS: PHYSICS LABORATORY(Any 5 Experiments)
1. Determination of Rigidity modulus ? Torsion pendulum
2. Determination of Young? s modulus by Non uniform bending method
3. (a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
4. Determination of thermal conductivity of a bad conductor ? Lee?s Disc method.
5. Determination of velocity of sound and compressibility of liquid ? Ultrasonic interferometer
6. Determination of wavelength of mercury spectrum ? spectrometer grating
7. Determination of band gap of a semiconductor
8. Determination of thickness of a thin wire ? Air wedge method




Completion of the course, the students will be able to: apply physics principles of optics and thermal physics
to evaluate engineering properties of materials.


COURSE OUTCOMES
COURSE OBJECTIVES
5

BS 8161 ? PHYSICS LABORATORY
CONTENTS

Sl.No. Name of the Experiment (any 5 experiments)
Page
No.
1.
Determination of Rigidity modulus ? Torsion pendulum
6
2.
Determination of Young ?s modulus by Non uniform bending method
12
3.
(a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
18
4.
Determination of thermal conductivity of a bad conductor ? Lee ?s Disc method.
28
5.
Determination of velocity of sound and compressibility of liquid ? Ultrasonic
interferometer
37
6.
Determination of wavelength of mercury spectrum ? spectrometer grating
42
7.
Determination of thickness of a thin wire ? Air wedge method
48
MEASURING INSTRUMENTS
M1 Screw gauge 54
M2 Vernier Calipers 58
M3 Travelling Microscope 62
M4 Spectrometer 66








6

TORSIONAL PENDULUM










7

Expt. No.1 TORSIONAL PENDULUM

AIM:
To determine the moment of inertia of the given disc and hence to determine the rigidity modulus of
the material of the given suspension wire by torsional oscillations
APPARATUS REQUIRED:
Torsional pendulum, two equal masses, stop clock, screw gauge and meter scale

FORMULA:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
where
m ?mass of the cylinder placed on the disc (kg)
To ?period of the pendulum for a length of l without mass (s)
T1?period of the pendulum for the same length when mass m is placed at a distance d 1
from the center of the suspension wire (s)
T2?period of the pendulum for the same length when mass m is placed at a distance d 2
from the center of the suspension wire (s)
a ? radius of the suspension wire (m)




8

1. To determine the time period of the disc:
Length of the wire (l)= --------
2
10
?
? m
Position of the equal
masses
Time for 10 oscillations Time period
(one oscillation)
s
Trial-1
s
Trial-2
s
Mean
s
Without any masses T0
With masses at
d1 = x10
-2
m
T1
With masses at
d2 = x10
-2
m
T2

2. To determine the radius of the wire:
Least count =0 .01 mm. Zero Error ZE = --------- divisions
Zero Correction ZC = ---------- mm

Sl.No.
Pitch Scale
Reading
PSR
3
10
?
? m
Head Scale
Coincidence
HSC
div
Observed reading
OR = PSR + (HSCXLC)
3
10
?
? m
Correct reading
CR = OR ? ZC
3
10
?
? m




Mean = ----------------
3
10
?
? m



9

PROCEDURE:
Torsional pendulum is suspended from vertical chuck. The length of the suspension wire is measured
between the vertical chuck and the chuck attached to the uniform circular disc (i). The circular disc is twisted
slightly without masses on the disc. Now it executes torsional oscillations. Care is taken to see that the disc
oscillates without wobbling. Time taken for 20 oscillations is noted with the help of a stop clock. Two trials are
taken. The average of these two trial readings is calculated from which the period of oscillations is found out
as T0.
Two identical cylindrical masses each of mass m are symmetrically placed on the disc on either side
of the wire at a distance d from the center of the disc. As before the disc is gently twisted. Time taken for 20
oscillations is noted from which the period of oscillation is calculated as T1.
The cylindrical masses are placed at a distance d2 from the center and the experiment is repeated.
The mean time period of oscillations is calculated T2.
The diameter of the specimen wire is measured accurately with the help of the screw gauge, at
various places on the wire. The average diameter and hence the radius of the wire is calculated as r.
Moment of inertia and the rigidity modulus are determined by the substituting the value of m, T 0, T1, T2,
T3, and l in the formula.










10

CALCULATION:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2

Mass of cylindrical mass, m = ----------- ? 10
-3
kg
Closest distance of the mass from the centre of the suspension wire, d1 = ------------ ? 10
-2
m
Farthest distance of the mass from the centre of suspension wire, d2= ------------? 10
-2
m
Period of oscillation without mass, To = ------------- s
Period of oscillation with mass at d1, T1= ------------ s
Period of oscillation with mass at d2, T2 = ------------- s

Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
= --------------- kg m
2
= --------------- kg m
2

Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
Moment of inertia, I = ------------------ kg m
2
Length of the wire, l = ------------------- ? 10
-2
m
Time of oscillation, To = ------------------ s
Radius of the wire, a = ------------------- ? 10
-3
m
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
= ----------------------
Rigidity modulus, n = ------------------- Nm
-2
11









RESULT:
(i)
The moment of inertia of the given circular disc, I = --------------- kg m
2
(ii)
The rigidity modulus of the material of the given wire, n = -------------- Nm
-2




1. State Hooke?s law.
2. Define ?Rigidity modulus
3. Define ?Moment of inertia
4. What is meant by torsional oscillation?
5. What is period of oscillation?
6. What is meant by twisting couple?
7. Define ? Shearing stress
8. Define ? Shearing strain
9. What is the unit of rigidity modulus?
10. What are the applications of torsional pendulum?


Viva ? voce
12


Young?s Modulus ? Non Uniform Bending
To determine depression (y):
L.C =.001cm M = ___________
3
10
?
? kg

Sl.No

Load


3
10
?
?
k
g
Microscope reading
Mean

2
10
?
? m
Depression
y for M kg

2
10
?
? m
Loading Unloading
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
1 W
2 W+50
3 W+100
4 W+150
5 W+200
6 W+250

Mean (y) = ----------
2
10
?
? m





13

Expt. No.2 YOUNG?S MODULUS BY NON ? UNIFORM BENDING
AIM:
To determine the young?s modulus of the material of the given bar, by non-uniform bending method
APPARATUS REQUIRED:
Travelling microscope, wooden bar, knife- edge, weights hanger, slotted weight, vernier calipers,
screw gauge and pin
FORMULA:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Where,
g ? acceleration due to gravity (9.8 ms
-2
)
l ? length of the bar between two knife edges (m)
b ? breadth of the bar (m)
d ? thickness of the bar (m)
y ? depressiont in the scale reading due to the change of mass M (m)
PROCEDURE:
The given wooden bar, for which young?s modulus is to be determined, is paced symmetrically on the
two knife edges. The distance between the knife edges is measured as the length of the bar (l). It is adjusted
to be, say, 60 cm. the weight hanger is suspended at the centre of the bar. A pin is held vertically at the
centre of the bar with the help of wax.
The given bar is brought to elastic mood by loading and unloading the bar with slotted weights in steps
of 50 g. This is repeated for two or three times. With the hanger as dead load W, the microscope is focused on
to the tip of the pin. The tangential screw of the microscope is adjusted so that the image of the tip of the pin
just touches the horizontal cross wire of the eyepiece. The main scale reading and the vernier scale
coincidence corresponding to this position are noted.
14

To find the breadth using vernier calipers, b:
Least count = ---------- cm Zero error = --------- div.
= ---------- ?10
-2
m Zero correction = ?ZE ?LC= --------- ?10
-2
m
Sl. No.

MSR
x 10
-2
m

VSC
div.
Observed reading
OR = MSR+(VSC ? LC)
x 10
-2
m
Correct Reading
CR = OR ? ZC
x 10
-2
m
1.

2.

3.


Mean, b = ------------------------?10
-2
m
To find the thickness using screw gauge, d:
Least count = ---------- mm Zero error = --------- div.
= ---------- ?10
-3
m Zero correction =ZE ?LC= --------- ?10
-3
m
Sl. No.

PSR
x 10
-3
m

HSC
div.
Observed reading
OR = PSR+ (HSC ? LC)
x 10
-3
m
Correct Reading
CR = OR ? ZC
x 10
-3
m
1.

2.

3.


Mean, d = ---------------------------?10
-3
m
15


The experiment is repeated by adding weights in steps of 50 g and every time the microscope is
adjusted for coincidence. The corresponding readings are noted. The experiment is repeated by unloading the
weights in steps of 50 g and the corresponding readings are tabulated. From this table, the shift in the scale
reading, say y, for a change of mass M is found out.
The breadth of the bar is measured at various points with the help of vernier calipers. Similarly the
thickness of the bar is measured by screw gauge. Substituting the values of M, y, l, d, b and g in the formula,
the young?s modulus of the material of the given bar is calculated.

















16

CALCULATION:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Acceleration due to gravity, g = 9.8 ms
-2
Length of the bar between two knife edges, l = ------------ ?10
-2
m
Breadth of the bar, b = ----------- ?10
-2
m
Thickness of the bar, d = ----------- ?10
-3
m
y = -----------?10
-2
m
E =
???? ?? 2
4?? ?? 3
?? Nm
-2

= ---------------
Young?s modulus, E = ----------- Nm
-2












17








RESULT:
Young?s modulus of the material of the given bar, E = ---------- Nm
-2


1. Define ? Young?s modulus
2. What is meant by Non-uniform bending?
3. Define ? Stress and strain
4. State Hooke?s law.
5. Define ? Neutral axis
6. What is the SI unit of young?s modulus?
7. Define ? Elastic limit
8. Define ? Elasticity
9. What are the factors affecting elasticity?
10. Define ? Elastic fatigue

Viva ? voce
18


To find the wavelength of the laser beam, ?:
Distance between the screen and the grating, D = ------------?10
-2
m
Number of lines per meter length of the grating, N = --------------- Lines per meter
Sl. No.
Order of diffraction,
(m)
Reading of the diffracted image
(?10
-2
m)
?? ?? = ?????? ?1
(
?? ?? ?? )
(deg.)
? =
?????? ?? ?? ????
m

Left side
(xi)
Right side
(xr)
Mean
(xm)










Mean, ? = ---------------- m


19

Expt. No.3(a) WAVELENGTH OF LASER LIGHT AND PARTICLE SIZE


AIM:
(i) To determine the wavelength of the given laser light.
(ii) To determine size of the given particle.
APPARATUS REQUIRED:
Diode laser, grating, screen, given micro particles, scale and screen.
FORMULAE:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
(ii) Grain size or diameter of the grain, 2d =
?????? ?? ?? m
Where
?? ?? ?angle of diffraction (deg.)
M ?order of diffraction (No unit)
N ?number of lines per metre length of the grating (m
-3
)
n ? order of diffraction (no unit)
? ? wavelength of laser light used (m)
D ? distance between the glass plate and the screen (m)
?? ?? - distance between the central bright spot and the nth fringe (m)
PROCEDURE:
TO FIND THE WAVELENGTH OF THE GIVEN LASER LIGHT:
The laser source, grating and screen are placed properly as shown in figure. The diode laser is kept
horizontally and switched on. Extreme care should be taken to avoid direct exposure of laser light on eyes.
20











21

The grating is held normal to the laser beam by adjusting the grating in such a way that the reflected
laser beam from the grating coincides with incident laser beam. Now the diffracted laser spots of various
orders can be seen on the screen, placed on the other side of the grating.

The distance of the different orders on either side of the central spot are measured as x randxi and are
tabulated.The mean value of xrandxiare calculated as xm for the m
th
order diffracted light. The distance
between the grating and the screen is measured as D. Hence, the angle of diffraction for the m
th
order,
?? ?? = ?????? ?1
(
?? ?? ?? )
The experiment is repeated for different orders and the readings are tabulated. From the table, ? for
each order is calculated. Substituting the value of ?, the corresponding order of diffraction and the number of
lines per meter length of the grating, the wavelength is calculated.

TO FIND THE SIZE OF THE GIVEN MICRO PARTICLE:

The lycopodium powder having fine micro particles of nearly same size is sprinkled on a glass plate.
This glass plate is kept between laser source and screen.
Now the particles present in the glass plate diffract laser beam from the source. By adjusting the
distance between the glass plate and the screen, a circular fringe pattern is obtained on the screen with
different orders of fingers. Now distance between the screen and the glass plate (D) is measured.
The distance of the first order and the second order fringe from the centre of spot are also measured.
Using the formula, the particle size is found out. The experiment is repeated for different D values.
22

To find the size of the particle:

CALCULATION:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
Number of lines per metre in the grating, N = ------------ lines per metre.
First order, m1; ?? 1
= ------------
Wavelength, ? =
?????? ?? 1
????
= ------------
Second order, m2; ?? 2
= ------------
Wavelength, ? =
?????? ?? 2
????
= ------------
Third order, m3; ?? 3
= ------------
Wavelength, ? =
?????? ?? 3
????
= ------------
Fourth order, m4; ?? 4
= ------------
Wavelength, ? =
?????? ?? 4
????
= -------------
Fifth order, m5; ?? 5
= ------------

Sl.No



Distance between
screen and glass
plate(D)
2
10
?
? m
Order of
diffraction
(n)
Distance between the
central bright spot and n
th

fringe (xn )
2
10
?
? m
Particle size
2
n
nD
d
x
?
?
m






23

Wavelength, ? =
?????? ?? 4
????
= ------------
Mean wavelength of the given laser light, ? = -------------- m
(ii) Grain size or diameter of the grain. 2d =
?????? ?? ??
Order of differaction, n = --------------
Wavelength of laser light used, ? = ------------- m
Distance between glass plate and the screen, D = ------------ m
Distance between central bright spot and the n
th
fringe,?? ?? = ------------ m
2d =
?????? ?? ??
=
= ------------ m








RESULT:
(i) Wavelength of the laser beam, ? = -------------- m
(ii) Average size of the particle = --------------- m

24


Optical fiber

To find numerical aperture, NA:

Sl. No.
Diameter of the circular patch
D(m)
Distance between the tip of the
fiber and the screen X (m)
NA =
?? (4?? 2
+?? 2
)
1
2





Mean NA =
Therefore, the acceptance angle, ? = Sin
-1
(NA) = -------------------
= -------------------


25

Expt. No.3(b) NUMERICAL APERTURE AND ACCEPTANCE ANGLE
AIM:
To measure the numerical aperture and the acceptance angle of the given fiber cable
APPARATUS REQUIRED:
Optical fiber cable with source, NA jig and in-line adaptor
FORMULA:
The numerical aperture, NA =
?? (4?? 2
+?? 2
)
1
2

Acceptance angle, ? = Sin
-1
(NA)
where,
D ? diameter of the circular patch (m)
X ? distance between the tip of the fiber and the screen (m)
PROCEDURE:
One end of the one metre fiber cable is connected to the laser light source and the other end
to the NA jig as shown in figure. The AC main is plugged in and the laser light is adjusted so that it appears at
the end of the fiber on the NA jig, the intensity knob is adjusted to get maximum intensity.
The white screen with the four concentric circles (10 mm, 20 mm, 30 mm and 40 mm diameter) is held
vertically at a suitable distance to make the red spot from the emitting fiber coincides with the 10 mm circle,
the diameter (D) of the spot is noted. The distance (X) of the screen from the fiber end is recorded.
The procedure is repeated for 20 mm, 30 mm, 40 mm diameter circles and the readings are tabulated.




26

















RESULT:
The numerical aperture, NA = ----------------
Acceptance angle, ? = ----------------




FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
2


PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science and fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems and use this knowledge to acquire
higher education.
2. Core competence
To train the students in Engineering Physics so as to apply their knowledge and training to compare,
and to analyze various engineering industrial problems for finding solutions.
3. Breadth
To provide relevant training and experience to bridge the gap between theoretical learning and
practice that enables them to find solutions for the real time problems in industry and to design products.
4. Professionalism
To inculcate professional and effective communication skills, leadership qualities and team spirit for
the students to make them multi-faceted personalities and develop their ability to relate engineering issues
to broader social context.
5. Lifelong learning/ethics
To demonstrate and practice ethical and professional responsibilities in the industry and society by
and large, through commitment and lifelong learning needed for successful professional career.





3


PROGRAMME OUTCOMES (POs)

a) To demonstrate and apply knowledge of Mathematics, Science and Engineering fundamentals in
Engineering physics
b) To determine the Moment of Inertia of given disc and Rigidity modulus of the given wire using
Torsional Pendulum
c) To determine Young?s modulus of a given bar using Non-Uniform bending
d) To utilize laser source and grating to estimate the wave length, particle size of given powder and
Numerical Aperture & acceptance angle of given optical fiber
e) To find the Thermal conductivity of a bad conductor using Lee?s Disc method
f) To Measure the velocity of ultrasonic wave in a liquid and compressibility of the liquid usingultrasonic
Interferometer
g) To determine the wavelength of Hg source using grating and spectrometer
h) To find the thickness of a thin wire using Air- wedge method
i) To participate and succeed in competitive exams and visualize and work on laboratory and
multidisciplinary tasks











4


BS 8161 ? PHYSICSLABORATORY
(Common to all branches of B.E. / B.TechProgrammes)
SYLLABUS


To introduce different experiments to test basic understanding of physics concepts applied in optics, thermal
physics, properties of matter and liquids.

LIST OF EXPERIMENTS: PHYSICS LABORATORY(Any 5 Experiments)
1. Determination of Rigidity modulus ? Torsion pendulum
2. Determination of Young? s modulus by Non uniform bending method
3. (a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
4. Determination of thermal conductivity of a bad conductor ? Lee?s Disc method.
5. Determination of velocity of sound and compressibility of liquid ? Ultrasonic interferometer
6. Determination of wavelength of mercury spectrum ? spectrometer grating
7. Determination of band gap of a semiconductor
8. Determination of thickness of a thin wire ? Air wedge method




Completion of the course, the students will be able to: apply physics principles of optics and thermal physics
to evaluate engineering properties of materials.


COURSE OUTCOMES
COURSE OBJECTIVES
5

BS 8161 ? PHYSICS LABORATORY
CONTENTS

Sl.No. Name of the Experiment (any 5 experiments)
Page
No.
1.
Determination of Rigidity modulus ? Torsion pendulum
6
2.
Determination of Young ?s modulus by Non uniform bending method
12
3.
(a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
18
4.
Determination of thermal conductivity of a bad conductor ? Lee ?s Disc method.
28
5.
Determination of velocity of sound and compressibility of liquid ? Ultrasonic
interferometer
37
6.
Determination of wavelength of mercury spectrum ? spectrometer grating
42
7.
Determination of thickness of a thin wire ? Air wedge method
48
MEASURING INSTRUMENTS
M1 Screw gauge 54
M2 Vernier Calipers 58
M3 Travelling Microscope 62
M4 Spectrometer 66








6

TORSIONAL PENDULUM










7

Expt. No.1 TORSIONAL PENDULUM

AIM:
To determine the moment of inertia of the given disc and hence to determine the rigidity modulus of
the material of the given suspension wire by torsional oscillations
APPARATUS REQUIRED:
Torsional pendulum, two equal masses, stop clock, screw gauge and meter scale

FORMULA:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
where
m ?mass of the cylinder placed on the disc (kg)
To ?period of the pendulum for a length of l without mass (s)
T1?period of the pendulum for the same length when mass m is placed at a distance d 1
from the center of the suspension wire (s)
T2?period of the pendulum for the same length when mass m is placed at a distance d 2
from the center of the suspension wire (s)
a ? radius of the suspension wire (m)




8

1. To determine the time period of the disc:
Length of the wire (l)= --------
2
10
?
? m
Position of the equal
masses
Time for 10 oscillations Time period
(one oscillation)
s
Trial-1
s
Trial-2
s
Mean
s
Without any masses T0
With masses at
d1 = x10
-2
m
T1
With masses at
d2 = x10
-2
m
T2

2. To determine the radius of the wire:
Least count =0 .01 mm. Zero Error ZE = --------- divisions
Zero Correction ZC = ---------- mm

Sl.No.
Pitch Scale
Reading
PSR
3
10
?
? m
Head Scale
Coincidence
HSC
div
Observed reading
OR = PSR + (HSCXLC)
3
10
?
? m
Correct reading
CR = OR ? ZC
3
10
?
? m




Mean = ----------------
3
10
?
? m



9

PROCEDURE:
Torsional pendulum is suspended from vertical chuck. The length of the suspension wire is measured
between the vertical chuck and the chuck attached to the uniform circular disc (i). The circular disc is twisted
slightly without masses on the disc. Now it executes torsional oscillations. Care is taken to see that the disc
oscillates without wobbling. Time taken for 20 oscillations is noted with the help of a stop clock. Two trials are
taken. The average of these two trial readings is calculated from which the period of oscillations is found out
as T0.
Two identical cylindrical masses each of mass m are symmetrically placed on the disc on either side
of the wire at a distance d from the center of the disc. As before the disc is gently twisted. Time taken for 20
oscillations is noted from which the period of oscillation is calculated as T1.
The cylindrical masses are placed at a distance d2 from the center and the experiment is repeated.
The mean time period of oscillations is calculated T2.
The diameter of the specimen wire is measured accurately with the help of the screw gauge, at
various places on the wire. The average diameter and hence the radius of the wire is calculated as r.
Moment of inertia and the rigidity modulus are determined by the substituting the value of m, T 0, T1, T2,
T3, and l in the formula.










10

CALCULATION:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2

Mass of cylindrical mass, m = ----------- ? 10
-3
kg
Closest distance of the mass from the centre of the suspension wire, d1 = ------------ ? 10
-2
m
Farthest distance of the mass from the centre of suspension wire, d2= ------------? 10
-2
m
Period of oscillation without mass, To = ------------- s
Period of oscillation with mass at d1, T1= ------------ s
Period of oscillation with mass at d2, T2 = ------------- s

Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
= --------------- kg m
2
= --------------- kg m
2

Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
Moment of inertia, I = ------------------ kg m
2
Length of the wire, l = ------------------- ? 10
-2
m
Time of oscillation, To = ------------------ s
Radius of the wire, a = ------------------- ? 10
-3
m
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
= ----------------------
Rigidity modulus, n = ------------------- Nm
-2
11









RESULT:
(i)
The moment of inertia of the given circular disc, I = --------------- kg m
2
(ii)
The rigidity modulus of the material of the given wire, n = -------------- Nm
-2




1. State Hooke?s law.
2. Define ?Rigidity modulus
3. Define ?Moment of inertia
4. What is meant by torsional oscillation?
5. What is period of oscillation?
6. What is meant by twisting couple?
7. Define ? Shearing stress
8. Define ? Shearing strain
9. What is the unit of rigidity modulus?
10. What are the applications of torsional pendulum?


Viva ? voce
12


Young?s Modulus ? Non Uniform Bending
To determine depression (y):
L.C =.001cm M = ___________
3
10
?
? kg

Sl.No

Load


3
10
?
?
k
g
Microscope reading
Mean

2
10
?
? m
Depression
y for M kg

2
10
?
? m
Loading Unloading
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
1 W
2 W+50
3 W+100
4 W+150
5 W+200
6 W+250

Mean (y) = ----------
2
10
?
? m





13

Expt. No.2 YOUNG?S MODULUS BY NON ? UNIFORM BENDING
AIM:
To determine the young?s modulus of the material of the given bar, by non-uniform bending method
APPARATUS REQUIRED:
Travelling microscope, wooden bar, knife- edge, weights hanger, slotted weight, vernier calipers,
screw gauge and pin
FORMULA:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Where,
g ? acceleration due to gravity (9.8 ms
-2
)
l ? length of the bar between two knife edges (m)
b ? breadth of the bar (m)
d ? thickness of the bar (m)
y ? depressiont in the scale reading due to the change of mass M (m)
PROCEDURE:
The given wooden bar, for which young?s modulus is to be determined, is paced symmetrically on the
two knife edges. The distance between the knife edges is measured as the length of the bar (l). It is adjusted
to be, say, 60 cm. the weight hanger is suspended at the centre of the bar. A pin is held vertically at the
centre of the bar with the help of wax.
The given bar is brought to elastic mood by loading and unloading the bar with slotted weights in steps
of 50 g. This is repeated for two or three times. With the hanger as dead load W, the microscope is focused on
to the tip of the pin. The tangential screw of the microscope is adjusted so that the image of the tip of the pin
just touches the horizontal cross wire of the eyepiece. The main scale reading and the vernier scale
coincidence corresponding to this position are noted.
14

To find the breadth using vernier calipers, b:
Least count = ---------- cm Zero error = --------- div.
= ---------- ?10
-2
m Zero correction = ?ZE ?LC= --------- ?10
-2
m
Sl. No.

MSR
x 10
-2
m

VSC
div.
Observed reading
OR = MSR+(VSC ? LC)
x 10
-2
m
Correct Reading
CR = OR ? ZC
x 10
-2
m
1.

2.

3.


Mean, b = ------------------------?10
-2
m
To find the thickness using screw gauge, d:
Least count = ---------- mm Zero error = --------- div.
= ---------- ?10
-3
m Zero correction =ZE ?LC= --------- ?10
-3
m
Sl. No.

PSR
x 10
-3
m

HSC
div.
Observed reading
OR = PSR+ (HSC ? LC)
x 10
-3
m
Correct Reading
CR = OR ? ZC
x 10
-3
m
1.

2.

3.


Mean, d = ---------------------------?10
-3
m
15


The experiment is repeated by adding weights in steps of 50 g and every time the microscope is
adjusted for coincidence. The corresponding readings are noted. The experiment is repeated by unloading the
weights in steps of 50 g and the corresponding readings are tabulated. From this table, the shift in the scale
reading, say y, for a change of mass M is found out.
The breadth of the bar is measured at various points with the help of vernier calipers. Similarly the
thickness of the bar is measured by screw gauge. Substituting the values of M, y, l, d, b and g in the formula,
the young?s modulus of the material of the given bar is calculated.

















16

CALCULATION:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Acceleration due to gravity, g = 9.8 ms
-2
Length of the bar between two knife edges, l = ------------ ?10
-2
m
Breadth of the bar, b = ----------- ?10
-2
m
Thickness of the bar, d = ----------- ?10
-3
m
y = -----------?10
-2
m
E =
???? ?? 2
4?? ?? 3
?? Nm
-2

= ---------------
Young?s modulus, E = ----------- Nm
-2












17








RESULT:
Young?s modulus of the material of the given bar, E = ---------- Nm
-2


1. Define ? Young?s modulus
2. What is meant by Non-uniform bending?
3. Define ? Stress and strain
4. State Hooke?s law.
5. Define ? Neutral axis
6. What is the SI unit of young?s modulus?
7. Define ? Elastic limit
8. Define ? Elasticity
9. What are the factors affecting elasticity?
10. Define ? Elastic fatigue

Viva ? voce
18


To find the wavelength of the laser beam, ?:
Distance between the screen and the grating, D = ------------?10
-2
m
Number of lines per meter length of the grating, N = --------------- Lines per meter
Sl. No.
Order of diffraction,
(m)
Reading of the diffracted image
(?10
-2
m)
?? ?? = ?????? ?1
(
?? ?? ?? )
(deg.)
? =
?????? ?? ?? ????
m

Left side
(xi)
Right side
(xr)
Mean
(xm)










Mean, ? = ---------------- m


19

Expt. No.3(a) WAVELENGTH OF LASER LIGHT AND PARTICLE SIZE


AIM:
(i) To determine the wavelength of the given laser light.
(ii) To determine size of the given particle.
APPARATUS REQUIRED:
Diode laser, grating, screen, given micro particles, scale and screen.
FORMULAE:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
(ii) Grain size or diameter of the grain, 2d =
?????? ?? ?? m
Where
?? ?? ?angle of diffraction (deg.)
M ?order of diffraction (No unit)
N ?number of lines per metre length of the grating (m
-3
)
n ? order of diffraction (no unit)
? ? wavelength of laser light used (m)
D ? distance between the glass plate and the screen (m)
?? ?? - distance between the central bright spot and the nth fringe (m)
PROCEDURE:
TO FIND THE WAVELENGTH OF THE GIVEN LASER LIGHT:
The laser source, grating and screen are placed properly as shown in figure. The diode laser is kept
horizontally and switched on. Extreme care should be taken to avoid direct exposure of laser light on eyes.
20











21

The grating is held normal to the laser beam by adjusting the grating in such a way that the reflected
laser beam from the grating coincides with incident laser beam. Now the diffracted laser spots of various
orders can be seen on the screen, placed on the other side of the grating.

The distance of the different orders on either side of the central spot are measured as x randxi and are
tabulated.The mean value of xrandxiare calculated as xm for the m
th
order diffracted light. The distance
between the grating and the screen is measured as D. Hence, the angle of diffraction for the m
th
order,
?? ?? = ?????? ?1
(
?? ?? ?? )
The experiment is repeated for different orders and the readings are tabulated. From the table, ? for
each order is calculated. Substituting the value of ?, the corresponding order of diffraction and the number of
lines per meter length of the grating, the wavelength is calculated.

TO FIND THE SIZE OF THE GIVEN MICRO PARTICLE:

The lycopodium powder having fine micro particles of nearly same size is sprinkled on a glass plate.
This glass plate is kept between laser source and screen.
Now the particles present in the glass plate diffract laser beam from the source. By adjusting the
distance between the glass plate and the screen, a circular fringe pattern is obtained on the screen with
different orders of fingers. Now distance between the screen and the glass plate (D) is measured.
The distance of the first order and the second order fringe from the centre of spot are also measured.
Using the formula, the particle size is found out. The experiment is repeated for different D values.
22

To find the size of the particle:

CALCULATION:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
Number of lines per metre in the grating, N = ------------ lines per metre.
First order, m1; ?? 1
= ------------
Wavelength, ? =
?????? ?? 1
????
= ------------
Second order, m2; ?? 2
= ------------
Wavelength, ? =
?????? ?? 2
????
= ------------
Third order, m3; ?? 3
= ------------
Wavelength, ? =
?????? ?? 3
????
= ------------
Fourth order, m4; ?? 4
= ------------
Wavelength, ? =
?????? ?? 4
????
= -------------
Fifth order, m5; ?? 5
= ------------

Sl.No



Distance between
screen and glass
plate(D)
2
10
?
? m
Order of
diffraction
(n)
Distance between the
central bright spot and n
th

fringe (xn )
2
10
?
? m
Particle size
2
n
nD
d
x
?
?
m






23

Wavelength, ? =
?????? ?? 4
????
= ------------
Mean wavelength of the given laser light, ? = -------------- m
(ii) Grain size or diameter of the grain. 2d =
?????? ?? ??
Order of differaction, n = --------------
Wavelength of laser light used, ? = ------------- m
Distance between glass plate and the screen, D = ------------ m
Distance between central bright spot and the n
th
fringe,?? ?? = ------------ m
2d =
?????? ?? ??
=
= ------------ m








RESULT:
(i) Wavelength of the laser beam, ? = -------------- m
(ii) Average size of the particle = --------------- m

24


Optical fiber

To find numerical aperture, NA:

Sl. No.
Diameter of the circular patch
D(m)
Distance between the tip of the
fiber and the screen X (m)
NA =
?? (4?? 2
+?? 2
)
1
2





Mean NA =
Therefore, the acceptance angle, ? = Sin
-1
(NA) = -------------------
= -------------------


25

Expt. No.3(b) NUMERICAL APERTURE AND ACCEPTANCE ANGLE
AIM:
To measure the numerical aperture and the acceptance angle of the given fiber cable
APPARATUS REQUIRED:
Optical fiber cable with source, NA jig and in-line adaptor
FORMULA:
The numerical aperture, NA =
?? (4?? 2
+?? 2
)
1
2

Acceptance angle, ? = Sin
-1
(NA)
where,
D ? diameter of the circular patch (m)
X ? distance between the tip of the fiber and the screen (m)
PROCEDURE:
One end of the one metre fiber cable is connected to the laser light source and the other end
to the NA jig as shown in figure. The AC main is plugged in and the laser light is adjusted so that it appears at
the end of the fiber on the NA jig, the intensity knob is adjusted to get maximum intensity.
The white screen with the four concentric circles (10 mm, 20 mm, 30 mm and 40 mm diameter) is held
vertically at a suitable distance to make the red spot from the emitting fiber coincides with the 10 mm circle,
the diameter (D) of the spot is noted. The distance (X) of the screen from the fiber end is recorded.
The procedure is repeated for 20 mm, 30 mm, 40 mm diameter circles and the readings are tabulated.




26

















RESULT:
The numerical aperture, NA = ----------------
Acceptance angle, ? = ----------------




27




1. What is semiconductor diode laser?
2. What is meant by active material in laser?
3. What is meant by LASER?
4. What is stimulated emission?
5. What are the characteristics of laser radiation?
6. What is homo?junction laser?
7. What is hetero?junction laser?
8. What are the applications of semiconductor laser?
9. What are the conditions required for laser action?
10. Define ? Numerical aperture







Viva ? voce
FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
2


PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science and fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems and use this knowledge to acquire
higher education.
2. Core competence
To train the students in Engineering Physics so as to apply their knowledge and training to compare,
and to analyze various engineering industrial problems for finding solutions.
3. Breadth
To provide relevant training and experience to bridge the gap between theoretical learning and
practice that enables them to find solutions for the real time problems in industry and to design products.
4. Professionalism
To inculcate professional and effective communication skills, leadership qualities and team spirit for
the students to make them multi-faceted personalities and develop their ability to relate engineering issues
to broader social context.
5. Lifelong learning/ethics
To demonstrate and practice ethical and professional responsibilities in the industry and society by
and large, through commitment and lifelong learning needed for successful professional career.





3


PROGRAMME OUTCOMES (POs)

a) To demonstrate and apply knowledge of Mathematics, Science and Engineering fundamentals in
Engineering physics
b) To determine the Moment of Inertia of given disc and Rigidity modulus of the given wire using
Torsional Pendulum
c) To determine Young?s modulus of a given bar using Non-Uniform bending
d) To utilize laser source and grating to estimate the wave length, particle size of given powder and
Numerical Aperture & acceptance angle of given optical fiber
e) To find the Thermal conductivity of a bad conductor using Lee?s Disc method
f) To Measure the velocity of ultrasonic wave in a liquid and compressibility of the liquid usingultrasonic
Interferometer
g) To determine the wavelength of Hg source using grating and spectrometer
h) To find the thickness of a thin wire using Air- wedge method
i) To participate and succeed in competitive exams and visualize and work on laboratory and
multidisciplinary tasks











4


BS 8161 ? PHYSICSLABORATORY
(Common to all branches of B.E. / B.TechProgrammes)
SYLLABUS


To introduce different experiments to test basic understanding of physics concepts applied in optics, thermal
physics, properties of matter and liquids.

LIST OF EXPERIMENTS: PHYSICS LABORATORY(Any 5 Experiments)
1. Determination of Rigidity modulus ? Torsion pendulum
2. Determination of Young? s modulus by Non uniform bending method
3. (a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
4. Determination of thermal conductivity of a bad conductor ? Lee?s Disc method.
5. Determination of velocity of sound and compressibility of liquid ? Ultrasonic interferometer
6. Determination of wavelength of mercury spectrum ? spectrometer grating
7. Determination of band gap of a semiconductor
8. Determination of thickness of a thin wire ? Air wedge method




Completion of the course, the students will be able to: apply physics principles of optics and thermal physics
to evaluate engineering properties of materials.


COURSE OUTCOMES
COURSE OBJECTIVES
5

BS 8161 ? PHYSICS LABORATORY
CONTENTS

Sl.No. Name of the Experiment (any 5 experiments)
Page
No.
1.
Determination of Rigidity modulus ? Torsion pendulum
6
2.
Determination of Young ?s modulus by Non uniform bending method
12
3.
(a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
18
4.
Determination of thermal conductivity of a bad conductor ? Lee ?s Disc method.
28
5.
Determination of velocity of sound and compressibility of liquid ? Ultrasonic
interferometer
37
6.
Determination of wavelength of mercury spectrum ? spectrometer grating
42
7.
Determination of thickness of a thin wire ? Air wedge method
48
MEASURING INSTRUMENTS
M1 Screw gauge 54
M2 Vernier Calipers 58
M3 Travelling Microscope 62
M4 Spectrometer 66








6

TORSIONAL PENDULUM










7

Expt. No.1 TORSIONAL PENDULUM

AIM:
To determine the moment of inertia of the given disc and hence to determine the rigidity modulus of
the material of the given suspension wire by torsional oscillations
APPARATUS REQUIRED:
Torsional pendulum, two equal masses, stop clock, screw gauge and meter scale

FORMULA:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
where
m ?mass of the cylinder placed on the disc (kg)
To ?period of the pendulum for a length of l without mass (s)
T1?period of the pendulum for the same length when mass m is placed at a distance d 1
from the center of the suspension wire (s)
T2?period of the pendulum for the same length when mass m is placed at a distance d 2
from the center of the suspension wire (s)
a ? radius of the suspension wire (m)




8

1. To determine the time period of the disc:
Length of the wire (l)= --------
2
10
?
? m
Position of the equal
masses
Time for 10 oscillations Time period
(one oscillation)
s
Trial-1
s
Trial-2
s
Mean
s
Without any masses T0
With masses at
d1 = x10
-2
m
T1
With masses at
d2 = x10
-2
m
T2

2. To determine the radius of the wire:
Least count =0 .01 mm. Zero Error ZE = --------- divisions
Zero Correction ZC = ---------- mm

Sl.No.
Pitch Scale
Reading
PSR
3
10
?
? m
Head Scale
Coincidence
HSC
div
Observed reading
OR = PSR + (HSCXLC)
3
10
?
? m
Correct reading
CR = OR ? ZC
3
10
?
? m




Mean = ----------------
3
10
?
? m



9

PROCEDURE:
Torsional pendulum is suspended from vertical chuck. The length of the suspension wire is measured
between the vertical chuck and the chuck attached to the uniform circular disc (i). The circular disc is twisted
slightly without masses on the disc. Now it executes torsional oscillations. Care is taken to see that the disc
oscillates without wobbling. Time taken for 20 oscillations is noted with the help of a stop clock. Two trials are
taken. The average of these two trial readings is calculated from which the period of oscillations is found out
as T0.
Two identical cylindrical masses each of mass m are symmetrically placed on the disc on either side
of the wire at a distance d from the center of the disc. As before the disc is gently twisted. Time taken for 20
oscillations is noted from which the period of oscillation is calculated as T1.
The cylindrical masses are placed at a distance d2 from the center and the experiment is repeated.
The mean time period of oscillations is calculated T2.
The diameter of the specimen wire is measured accurately with the help of the screw gauge, at
various places on the wire. The average diameter and hence the radius of the wire is calculated as r.
Moment of inertia and the rigidity modulus are determined by the substituting the value of m, T 0, T1, T2,
T3, and l in the formula.










10

CALCULATION:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2

Mass of cylindrical mass, m = ----------- ? 10
-3
kg
Closest distance of the mass from the centre of the suspension wire, d1 = ------------ ? 10
-2
m
Farthest distance of the mass from the centre of suspension wire, d2= ------------? 10
-2
m
Period of oscillation without mass, To = ------------- s
Period of oscillation with mass at d1, T1= ------------ s
Period of oscillation with mass at d2, T2 = ------------- s

Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
= --------------- kg m
2
= --------------- kg m
2

Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
Moment of inertia, I = ------------------ kg m
2
Length of the wire, l = ------------------- ? 10
-2
m
Time of oscillation, To = ------------------ s
Radius of the wire, a = ------------------- ? 10
-3
m
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
= ----------------------
Rigidity modulus, n = ------------------- Nm
-2
11









RESULT:
(i)
The moment of inertia of the given circular disc, I = --------------- kg m
2
(ii)
The rigidity modulus of the material of the given wire, n = -------------- Nm
-2




1. State Hooke?s law.
2. Define ?Rigidity modulus
3. Define ?Moment of inertia
4. What is meant by torsional oscillation?
5. What is period of oscillation?
6. What is meant by twisting couple?
7. Define ? Shearing stress
8. Define ? Shearing strain
9. What is the unit of rigidity modulus?
10. What are the applications of torsional pendulum?


Viva ? voce
12


Young?s Modulus ? Non Uniform Bending
To determine depression (y):
L.C =.001cm M = ___________
3
10
?
? kg

Sl.No

Load


3
10
?
?
k
g
Microscope reading
Mean

2
10
?
? m
Depression
y for M kg

2
10
?
? m
Loading Unloading
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
1 W
2 W+50
3 W+100
4 W+150
5 W+200
6 W+250

Mean (y) = ----------
2
10
?
? m





13

Expt. No.2 YOUNG?S MODULUS BY NON ? UNIFORM BENDING
AIM:
To determine the young?s modulus of the material of the given bar, by non-uniform bending method
APPARATUS REQUIRED:
Travelling microscope, wooden bar, knife- edge, weights hanger, slotted weight, vernier calipers,
screw gauge and pin
FORMULA:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Where,
g ? acceleration due to gravity (9.8 ms
-2
)
l ? length of the bar between two knife edges (m)
b ? breadth of the bar (m)
d ? thickness of the bar (m)
y ? depressiont in the scale reading due to the change of mass M (m)
PROCEDURE:
The given wooden bar, for which young?s modulus is to be determined, is paced symmetrically on the
two knife edges. The distance between the knife edges is measured as the length of the bar (l). It is adjusted
to be, say, 60 cm. the weight hanger is suspended at the centre of the bar. A pin is held vertically at the
centre of the bar with the help of wax.
The given bar is brought to elastic mood by loading and unloading the bar with slotted weights in steps
of 50 g. This is repeated for two or three times. With the hanger as dead load W, the microscope is focused on
to the tip of the pin. The tangential screw of the microscope is adjusted so that the image of the tip of the pin
just touches the horizontal cross wire of the eyepiece. The main scale reading and the vernier scale
coincidence corresponding to this position are noted.
14

To find the breadth using vernier calipers, b:
Least count = ---------- cm Zero error = --------- div.
= ---------- ?10
-2
m Zero correction = ?ZE ?LC= --------- ?10
-2
m
Sl. No.

MSR
x 10
-2
m

VSC
div.
Observed reading
OR = MSR+(VSC ? LC)
x 10
-2
m
Correct Reading
CR = OR ? ZC
x 10
-2
m
1.

2.

3.


Mean, b = ------------------------?10
-2
m
To find the thickness using screw gauge, d:
Least count = ---------- mm Zero error = --------- div.
= ---------- ?10
-3
m Zero correction =ZE ?LC= --------- ?10
-3
m
Sl. No.

PSR
x 10
-3
m

HSC
div.
Observed reading
OR = PSR+ (HSC ? LC)
x 10
-3
m
Correct Reading
CR = OR ? ZC
x 10
-3
m
1.

2.

3.


Mean, d = ---------------------------?10
-3
m
15


The experiment is repeated by adding weights in steps of 50 g and every time the microscope is
adjusted for coincidence. The corresponding readings are noted. The experiment is repeated by unloading the
weights in steps of 50 g and the corresponding readings are tabulated. From this table, the shift in the scale
reading, say y, for a change of mass M is found out.
The breadth of the bar is measured at various points with the help of vernier calipers. Similarly the
thickness of the bar is measured by screw gauge. Substituting the values of M, y, l, d, b and g in the formula,
the young?s modulus of the material of the given bar is calculated.

















16

CALCULATION:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Acceleration due to gravity, g = 9.8 ms
-2
Length of the bar between two knife edges, l = ------------ ?10
-2
m
Breadth of the bar, b = ----------- ?10
-2
m
Thickness of the bar, d = ----------- ?10
-3
m
y = -----------?10
-2
m
E =
???? ?? 2
4?? ?? 3
?? Nm
-2

= ---------------
Young?s modulus, E = ----------- Nm
-2












17








RESULT:
Young?s modulus of the material of the given bar, E = ---------- Nm
-2


1. Define ? Young?s modulus
2. What is meant by Non-uniform bending?
3. Define ? Stress and strain
4. State Hooke?s law.
5. Define ? Neutral axis
6. What is the SI unit of young?s modulus?
7. Define ? Elastic limit
8. Define ? Elasticity
9. What are the factors affecting elasticity?
10. Define ? Elastic fatigue

Viva ? voce
18


To find the wavelength of the laser beam, ?:
Distance between the screen and the grating, D = ------------?10
-2
m
Number of lines per meter length of the grating, N = --------------- Lines per meter
Sl. No.
Order of diffraction,
(m)
Reading of the diffracted image
(?10
-2
m)
?? ?? = ?????? ?1
(
?? ?? ?? )
(deg.)
? =
?????? ?? ?? ????
m

Left side
(xi)
Right side
(xr)
Mean
(xm)










Mean, ? = ---------------- m


19

Expt. No.3(a) WAVELENGTH OF LASER LIGHT AND PARTICLE SIZE


AIM:
(i) To determine the wavelength of the given laser light.
(ii) To determine size of the given particle.
APPARATUS REQUIRED:
Diode laser, grating, screen, given micro particles, scale and screen.
FORMULAE:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
(ii) Grain size or diameter of the grain, 2d =
?????? ?? ?? m
Where
?? ?? ?angle of diffraction (deg.)
M ?order of diffraction (No unit)
N ?number of lines per metre length of the grating (m
-3
)
n ? order of diffraction (no unit)
? ? wavelength of laser light used (m)
D ? distance between the glass plate and the screen (m)
?? ?? - distance between the central bright spot and the nth fringe (m)
PROCEDURE:
TO FIND THE WAVELENGTH OF THE GIVEN LASER LIGHT:
The laser source, grating and screen are placed properly as shown in figure. The diode laser is kept
horizontally and switched on. Extreme care should be taken to avoid direct exposure of laser light on eyes.
20











21

The grating is held normal to the laser beam by adjusting the grating in such a way that the reflected
laser beam from the grating coincides with incident laser beam. Now the diffracted laser spots of various
orders can be seen on the screen, placed on the other side of the grating.

The distance of the different orders on either side of the central spot are measured as x randxi and are
tabulated.The mean value of xrandxiare calculated as xm for the m
th
order diffracted light. The distance
between the grating and the screen is measured as D. Hence, the angle of diffraction for the m
th
order,
?? ?? = ?????? ?1
(
?? ?? ?? )
The experiment is repeated for different orders and the readings are tabulated. From the table, ? for
each order is calculated. Substituting the value of ?, the corresponding order of diffraction and the number of
lines per meter length of the grating, the wavelength is calculated.

TO FIND THE SIZE OF THE GIVEN MICRO PARTICLE:

The lycopodium powder having fine micro particles of nearly same size is sprinkled on a glass plate.
This glass plate is kept between laser source and screen.
Now the particles present in the glass plate diffract laser beam from the source. By adjusting the
distance between the glass plate and the screen, a circular fringe pattern is obtained on the screen with
different orders of fingers. Now distance between the screen and the glass plate (D) is measured.
The distance of the first order and the second order fringe from the centre of spot are also measured.
Using the formula, the particle size is found out. The experiment is repeated for different D values.
22

To find the size of the particle:

CALCULATION:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
Number of lines per metre in the grating, N = ------------ lines per metre.
First order, m1; ?? 1
= ------------
Wavelength, ? =
?????? ?? 1
????
= ------------
Second order, m2; ?? 2
= ------------
Wavelength, ? =
?????? ?? 2
????
= ------------
Third order, m3; ?? 3
= ------------
Wavelength, ? =
?????? ?? 3
????
= ------------
Fourth order, m4; ?? 4
= ------------
Wavelength, ? =
?????? ?? 4
????
= -------------
Fifth order, m5; ?? 5
= ------------

Sl.No



Distance between
screen and glass
plate(D)
2
10
?
? m
Order of
diffraction
(n)
Distance between the
central bright spot and n
th

fringe (xn )
2
10
?
? m
Particle size
2
n
nD
d
x
?
?
m






23

Wavelength, ? =
?????? ?? 4
????
= ------------
Mean wavelength of the given laser light, ? = -------------- m
(ii) Grain size or diameter of the grain. 2d =
?????? ?? ??
Order of differaction, n = --------------
Wavelength of laser light used, ? = ------------- m
Distance between glass plate and the screen, D = ------------ m
Distance between central bright spot and the n
th
fringe,?? ?? = ------------ m
2d =
?????? ?? ??
=
= ------------ m








RESULT:
(i) Wavelength of the laser beam, ? = -------------- m
(ii) Average size of the particle = --------------- m

24


Optical fiber

To find numerical aperture, NA:

Sl. No.
Diameter of the circular patch
D(m)
Distance between the tip of the
fiber and the screen X (m)
NA =
?? (4?? 2
+?? 2
)
1
2





Mean NA =
Therefore, the acceptance angle, ? = Sin
-1
(NA) = -------------------
= -------------------


25

Expt. No.3(b) NUMERICAL APERTURE AND ACCEPTANCE ANGLE
AIM:
To measure the numerical aperture and the acceptance angle of the given fiber cable
APPARATUS REQUIRED:
Optical fiber cable with source, NA jig and in-line adaptor
FORMULA:
The numerical aperture, NA =
?? (4?? 2
+?? 2
)
1
2

Acceptance angle, ? = Sin
-1
(NA)
where,
D ? diameter of the circular patch (m)
X ? distance between the tip of the fiber and the screen (m)
PROCEDURE:
One end of the one metre fiber cable is connected to the laser light source and the other end
to the NA jig as shown in figure. The AC main is plugged in and the laser light is adjusted so that it appears at
the end of the fiber on the NA jig, the intensity knob is adjusted to get maximum intensity.
The white screen with the four concentric circles (10 mm, 20 mm, 30 mm and 40 mm diameter) is held
vertically at a suitable distance to make the red spot from the emitting fiber coincides with the 10 mm circle,
the diameter (D) of the spot is noted. The distance (X) of the screen from the fiber end is recorded.
The procedure is repeated for 20 mm, 30 mm, 40 mm diameter circles and the readings are tabulated.




26

















RESULT:
The numerical aperture, NA = ----------------
Acceptance angle, ? = ----------------




27




1. What is semiconductor diode laser?
2. What is meant by active material in laser?
3. What is meant by LASER?
4. What is stimulated emission?
5. What are the characteristics of laser radiation?
6. What is homo?junction laser?
7. What is hetero?junction laser?
8. What are the applications of semiconductor laser?
9. What are the conditions required for laser action?
10. Define ? Numerical aperture







Viva ? voce
28


Lee?s disc setup


FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
2


PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science and fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems and use this knowledge to acquire
higher education.
2. Core competence
To train the students in Engineering Physics so as to apply their knowledge and training to compare,
and to analyze various engineering industrial problems for finding solutions.
3. Breadth
To provide relevant training and experience to bridge the gap between theoretical learning and
practice that enables them to find solutions for the real time problems in industry and to design products.
4. Professionalism
To inculcate professional and effective communication skills, leadership qualities and team spirit for
the students to make them multi-faceted personalities and develop their ability to relate engineering issues
to broader social context.
5. Lifelong learning/ethics
To demonstrate and practice ethical and professional responsibilities in the industry and society by
and large, through commitment and lifelong learning needed for successful professional career.





3


PROGRAMME OUTCOMES (POs)

a) To demonstrate and apply knowledge of Mathematics, Science and Engineering fundamentals in
Engineering physics
b) To determine the Moment of Inertia of given disc and Rigidity modulus of the given wire using
Torsional Pendulum
c) To determine Young?s modulus of a given bar using Non-Uniform bending
d) To utilize laser source and grating to estimate the wave length, particle size of given powder and
Numerical Aperture & acceptance angle of given optical fiber
e) To find the Thermal conductivity of a bad conductor using Lee?s Disc method
f) To Measure the velocity of ultrasonic wave in a liquid and compressibility of the liquid usingultrasonic
Interferometer
g) To determine the wavelength of Hg source using grating and spectrometer
h) To find the thickness of a thin wire using Air- wedge method
i) To participate and succeed in competitive exams and visualize and work on laboratory and
multidisciplinary tasks











4


BS 8161 ? PHYSICSLABORATORY
(Common to all branches of B.E. / B.TechProgrammes)
SYLLABUS


To introduce different experiments to test basic understanding of physics concepts applied in optics, thermal
physics, properties of matter and liquids.

LIST OF EXPERIMENTS: PHYSICS LABORATORY(Any 5 Experiments)
1. Determination of Rigidity modulus ? Torsion pendulum
2. Determination of Young? s modulus by Non uniform bending method
3. (a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
4. Determination of thermal conductivity of a bad conductor ? Lee?s Disc method.
5. Determination of velocity of sound and compressibility of liquid ? Ultrasonic interferometer
6. Determination of wavelength of mercury spectrum ? spectrometer grating
7. Determination of band gap of a semiconductor
8. Determination of thickness of a thin wire ? Air wedge method




Completion of the course, the students will be able to: apply physics principles of optics and thermal physics
to evaluate engineering properties of materials.


COURSE OUTCOMES
COURSE OBJECTIVES
5

BS 8161 ? PHYSICS LABORATORY
CONTENTS

Sl.No. Name of the Experiment (any 5 experiments)
Page
No.
1.
Determination of Rigidity modulus ? Torsion pendulum
6
2.
Determination of Young ?s modulus by Non uniform bending method
12
3.
(a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
18
4.
Determination of thermal conductivity of a bad conductor ? Lee ?s Disc method.
28
5.
Determination of velocity of sound and compressibility of liquid ? Ultrasonic
interferometer
37
6.
Determination of wavelength of mercury spectrum ? spectrometer grating
42
7.
Determination of thickness of a thin wire ? Air wedge method
48
MEASURING INSTRUMENTS
M1 Screw gauge 54
M2 Vernier Calipers 58
M3 Travelling Microscope 62
M4 Spectrometer 66








6

TORSIONAL PENDULUM










7

Expt. No.1 TORSIONAL PENDULUM

AIM:
To determine the moment of inertia of the given disc and hence to determine the rigidity modulus of
the material of the given suspension wire by torsional oscillations
APPARATUS REQUIRED:
Torsional pendulum, two equal masses, stop clock, screw gauge and meter scale

FORMULA:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
where
m ?mass of the cylinder placed on the disc (kg)
To ?period of the pendulum for a length of l without mass (s)
T1?period of the pendulum for the same length when mass m is placed at a distance d 1
from the center of the suspension wire (s)
T2?period of the pendulum for the same length when mass m is placed at a distance d 2
from the center of the suspension wire (s)
a ? radius of the suspension wire (m)




8

1. To determine the time period of the disc:
Length of the wire (l)= --------
2
10
?
? m
Position of the equal
masses
Time for 10 oscillations Time period
(one oscillation)
s
Trial-1
s
Trial-2
s
Mean
s
Without any masses T0
With masses at
d1 = x10
-2
m
T1
With masses at
d2 = x10
-2
m
T2

2. To determine the radius of the wire:
Least count =0 .01 mm. Zero Error ZE = --------- divisions
Zero Correction ZC = ---------- mm

Sl.No.
Pitch Scale
Reading
PSR
3
10
?
? m
Head Scale
Coincidence
HSC
div
Observed reading
OR = PSR + (HSCXLC)
3
10
?
? m
Correct reading
CR = OR ? ZC
3
10
?
? m




Mean = ----------------
3
10
?
? m



9

PROCEDURE:
Torsional pendulum is suspended from vertical chuck. The length of the suspension wire is measured
between the vertical chuck and the chuck attached to the uniform circular disc (i). The circular disc is twisted
slightly without masses on the disc. Now it executes torsional oscillations. Care is taken to see that the disc
oscillates without wobbling. Time taken for 20 oscillations is noted with the help of a stop clock. Two trials are
taken. The average of these two trial readings is calculated from which the period of oscillations is found out
as T0.
Two identical cylindrical masses each of mass m are symmetrically placed on the disc on either side
of the wire at a distance d from the center of the disc. As before the disc is gently twisted. Time taken for 20
oscillations is noted from which the period of oscillation is calculated as T1.
The cylindrical masses are placed at a distance d2 from the center and the experiment is repeated.
The mean time period of oscillations is calculated T2.
The diameter of the specimen wire is measured accurately with the help of the screw gauge, at
various places on the wire. The average diameter and hence the radius of the wire is calculated as r.
Moment of inertia and the rigidity modulus are determined by the substituting the value of m, T 0, T1, T2,
T3, and l in the formula.










10

CALCULATION:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2

Mass of cylindrical mass, m = ----------- ? 10
-3
kg
Closest distance of the mass from the centre of the suspension wire, d1 = ------------ ? 10
-2
m
Farthest distance of the mass from the centre of suspension wire, d2= ------------? 10
-2
m
Period of oscillation without mass, To = ------------- s
Period of oscillation with mass at d1, T1= ------------ s
Period of oscillation with mass at d2, T2 = ------------- s

Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
= --------------- kg m
2
= --------------- kg m
2

Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
Moment of inertia, I = ------------------ kg m
2
Length of the wire, l = ------------------- ? 10
-2
m
Time of oscillation, To = ------------------ s
Radius of the wire, a = ------------------- ? 10
-3
m
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
= ----------------------
Rigidity modulus, n = ------------------- Nm
-2
11









RESULT:
(i)
The moment of inertia of the given circular disc, I = --------------- kg m
2
(ii)
The rigidity modulus of the material of the given wire, n = -------------- Nm
-2




1. State Hooke?s law.
2. Define ?Rigidity modulus
3. Define ?Moment of inertia
4. What is meant by torsional oscillation?
5. What is period of oscillation?
6. What is meant by twisting couple?
7. Define ? Shearing stress
8. Define ? Shearing strain
9. What is the unit of rigidity modulus?
10. What are the applications of torsional pendulum?


Viva ? voce
12


Young?s Modulus ? Non Uniform Bending
To determine depression (y):
L.C =.001cm M = ___________
3
10
?
? kg

Sl.No

Load


3
10
?
?
k
g
Microscope reading
Mean

2
10
?
? m
Depression
y for M kg

2
10
?
? m
Loading Unloading
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
1 W
2 W+50
3 W+100
4 W+150
5 W+200
6 W+250

Mean (y) = ----------
2
10
?
? m





13

Expt. No.2 YOUNG?S MODULUS BY NON ? UNIFORM BENDING
AIM:
To determine the young?s modulus of the material of the given bar, by non-uniform bending method
APPARATUS REQUIRED:
Travelling microscope, wooden bar, knife- edge, weights hanger, slotted weight, vernier calipers,
screw gauge and pin
FORMULA:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Where,
g ? acceleration due to gravity (9.8 ms
-2
)
l ? length of the bar between two knife edges (m)
b ? breadth of the bar (m)
d ? thickness of the bar (m)
y ? depressiont in the scale reading due to the change of mass M (m)
PROCEDURE:
The given wooden bar, for which young?s modulus is to be determined, is paced symmetrically on the
two knife edges. The distance between the knife edges is measured as the length of the bar (l). It is adjusted
to be, say, 60 cm. the weight hanger is suspended at the centre of the bar. A pin is held vertically at the
centre of the bar with the help of wax.
The given bar is brought to elastic mood by loading and unloading the bar with slotted weights in steps
of 50 g. This is repeated for two or three times. With the hanger as dead load W, the microscope is focused on
to the tip of the pin. The tangential screw of the microscope is adjusted so that the image of the tip of the pin
just touches the horizontal cross wire of the eyepiece. The main scale reading and the vernier scale
coincidence corresponding to this position are noted.
14

To find the breadth using vernier calipers, b:
Least count = ---------- cm Zero error = --------- div.
= ---------- ?10
-2
m Zero correction = ?ZE ?LC= --------- ?10
-2
m
Sl. No.

MSR
x 10
-2
m

VSC
div.
Observed reading
OR = MSR+(VSC ? LC)
x 10
-2
m
Correct Reading
CR = OR ? ZC
x 10
-2
m
1.

2.

3.


Mean, b = ------------------------?10
-2
m
To find the thickness using screw gauge, d:
Least count = ---------- mm Zero error = --------- div.
= ---------- ?10
-3
m Zero correction =ZE ?LC= --------- ?10
-3
m
Sl. No.

PSR
x 10
-3
m

HSC
div.
Observed reading
OR = PSR+ (HSC ? LC)
x 10
-3
m
Correct Reading
CR = OR ? ZC
x 10
-3
m
1.

2.

3.


Mean, d = ---------------------------?10
-3
m
15


The experiment is repeated by adding weights in steps of 50 g and every time the microscope is
adjusted for coincidence. The corresponding readings are noted. The experiment is repeated by unloading the
weights in steps of 50 g and the corresponding readings are tabulated. From this table, the shift in the scale
reading, say y, for a change of mass M is found out.
The breadth of the bar is measured at various points with the help of vernier calipers. Similarly the
thickness of the bar is measured by screw gauge. Substituting the values of M, y, l, d, b and g in the formula,
the young?s modulus of the material of the given bar is calculated.

















16

CALCULATION:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Acceleration due to gravity, g = 9.8 ms
-2
Length of the bar between two knife edges, l = ------------ ?10
-2
m
Breadth of the bar, b = ----------- ?10
-2
m
Thickness of the bar, d = ----------- ?10
-3
m
y = -----------?10
-2
m
E =
???? ?? 2
4?? ?? 3
?? Nm
-2

= ---------------
Young?s modulus, E = ----------- Nm
-2












17








RESULT:
Young?s modulus of the material of the given bar, E = ---------- Nm
-2


1. Define ? Young?s modulus
2. What is meant by Non-uniform bending?
3. Define ? Stress and strain
4. State Hooke?s law.
5. Define ? Neutral axis
6. What is the SI unit of young?s modulus?
7. Define ? Elastic limit
8. Define ? Elasticity
9. What are the factors affecting elasticity?
10. Define ? Elastic fatigue

Viva ? voce
18


To find the wavelength of the laser beam, ?:
Distance between the screen and the grating, D = ------------?10
-2
m
Number of lines per meter length of the grating, N = --------------- Lines per meter
Sl. No.
Order of diffraction,
(m)
Reading of the diffracted image
(?10
-2
m)
?? ?? = ?????? ?1
(
?? ?? ?? )
(deg.)
? =
?????? ?? ?? ????
m

Left side
(xi)
Right side
(xr)
Mean
(xm)










Mean, ? = ---------------- m


19

Expt. No.3(a) WAVELENGTH OF LASER LIGHT AND PARTICLE SIZE


AIM:
(i) To determine the wavelength of the given laser light.
(ii) To determine size of the given particle.
APPARATUS REQUIRED:
Diode laser, grating, screen, given micro particles, scale and screen.
FORMULAE:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
(ii) Grain size or diameter of the grain, 2d =
?????? ?? ?? m
Where
?? ?? ?angle of diffraction (deg.)
M ?order of diffraction (No unit)
N ?number of lines per metre length of the grating (m
-3
)
n ? order of diffraction (no unit)
? ? wavelength of laser light used (m)
D ? distance between the glass plate and the screen (m)
?? ?? - distance between the central bright spot and the nth fringe (m)
PROCEDURE:
TO FIND THE WAVELENGTH OF THE GIVEN LASER LIGHT:
The laser source, grating and screen are placed properly as shown in figure. The diode laser is kept
horizontally and switched on. Extreme care should be taken to avoid direct exposure of laser light on eyes.
20











21

The grating is held normal to the laser beam by adjusting the grating in such a way that the reflected
laser beam from the grating coincides with incident laser beam. Now the diffracted laser spots of various
orders can be seen on the screen, placed on the other side of the grating.

The distance of the different orders on either side of the central spot are measured as x randxi and are
tabulated.The mean value of xrandxiare calculated as xm for the m
th
order diffracted light. The distance
between the grating and the screen is measured as D. Hence, the angle of diffraction for the m
th
order,
?? ?? = ?????? ?1
(
?? ?? ?? )
The experiment is repeated for different orders and the readings are tabulated. From the table, ? for
each order is calculated. Substituting the value of ?, the corresponding order of diffraction and the number of
lines per meter length of the grating, the wavelength is calculated.

TO FIND THE SIZE OF THE GIVEN MICRO PARTICLE:

The lycopodium powder having fine micro particles of nearly same size is sprinkled on a glass plate.
This glass plate is kept between laser source and screen.
Now the particles present in the glass plate diffract laser beam from the source. By adjusting the
distance between the glass plate and the screen, a circular fringe pattern is obtained on the screen with
different orders of fingers. Now distance between the screen and the glass plate (D) is measured.
The distance of the first order and the second order fringe from the centre of spot are also measured.
Using the formula, the particle size is found out. The experiment is repeated for different D values.
22

To find the size of the particle:

CALCULATION:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
Number of lines per metre in the grating, N = ------------ lines per metre.
First order, m1; ?? 1
= ------------
Wavelength, ? =
?????? ?? 1
????
= ------------
Second order, m2; ?? 2
= ------------
Wavelength, ? =
?????? ?? 2
????
= ------------
Third order, m3; ?? 3
= ------------
Wavelength, ? =
?????? ?? 3
????
= ------------
Fourth order, m4; ?? 4
= ------------
Wavelength, ? =
?????? ?? 4
????
= -------------
Fifth order, m5; ?? 5
= ------------

Sl.No



Distance between
screen and glass
plate(D)
2
10
?
? m
Order of
diffraction
(n)
Distance between the
central bright spot and n
th

fringe (xn )
2
10
?
? m
Particle size
2
n
nD
d
x
?
?
m






23

Wavelength, ? =
?????? ?? 4
????
= ------------
Mean wavelength of the given laser light, ? = -------------- m
(ii) Grain size or diameter of the grain. 2d =
?????? ?? ??
Order of differaction, n = --------------
Wavelength of laser light used, ? = ------------- m
Distance between glass plate and the screen, D = ------------ m
Distance between central bright spot and the n
th
fringe,?? ?? = ------------ m
2d =
?????? ?? ??
=
= ------------ m








RESULT:
(i) Wavelength of the laser beam, ? = -------------- m
(ii) Average size of the particle = --------------- m

24


Optical fiber

To find numerical aperture, NA:

Sl. No.
Diameter of the circular patch
D(m)
Distance between the tip of the
fiber and the screen X (m)
NA =
?? (4?? 2
+?? 2
)
1
2





Mean NA =
Therefore, the acceptance angle, ? = Sin
-1
(NA) = -------------------
= -------------------


25

Expt. No.3(b) NUMERICAL APERTURE AND ACCEPTANCE ANGLE
AIM:
To measure the numerical aperture and the acceptance angle of the given fiber cable
APPARATUS REQUIRED:
Optical fiber cable with source, NA jig and in-line adaptor
FORMULA:
The numerical aperture, NA =
?? (4?? 2
+?? 2
)
1
2

Acceptance angle, ? = Sin
-1
(NA)
where,
D ? diameter of the circular patch (m)
X ? distance between the tip of the fiber and the screen (m)
PROCEDURE:
One end of the one metre fiber cable is connected to the laser light source and the other end
to the NA jig as shown in figure. The AC main is plugged in and the laser light is adjusted so that it appears at
the end of the fiber on the NA jig, the intensity knob is adjusted to get maximum intensity.
The white screen with the four concentric circles (10 mm, 20 mm, 30 mm and 40 mm diameter) is held
vertically at a suitable distance to make the red spot from the emitting fiber coincides with the 10 mm circle,
the diameter (D) of the spot is noted. The distance (X) of the screen from the fiber end is recorded.
The procedure is repeated for 20 mm, 30 mm, 40 mm diameter circles and the readings are tabulated.




26

















RESULT:
The numerical aperture, NA = ----------------
Acceptance angle, ? = ----------------




27




1. What is semiconductor diode laser?
2. What is meant by active material in laser?
3. What is meant by LASER?
4. What is stimulated emission?
5. What are the characteristics of laser radiation?
6. What is homo?junction laser?
7. What is hetero?junction laser?
8. What are the applications of semiconductor laser?
9. What are the conditions required for laser action?
10. Define ? Numerical aperture







Viva ? voce
28


Lee?s disc setup


29

Expt. No. 4 THERMAL CONDUCTIVITY OF A BAD CONDUCTOR
BY LEE?S DISC METHOD

AIM:
To determine the coefficient of thermal conductivity of a bad conductor
APPARATUS REQUIRED:
Lee?s disc apparatus, bad conductors, stop-clock, thermometers, screw gauge, vernier calipers and
steam boiler
FORMULA:
Thermal conductivity of a bad conductor,
? ?
? ? ? ?
1 1
2 1
2
2 2
2
? ?
? ?
?
?
?
?
?
?
?
?
?
? k Wm
h r r
h r d
dt
d
MS
K
? ? ?
?

M ? Mass of the metallic disc (Kg)
S ? Specific heat capacity of the metallic disc ( J Kg
-1
K
-1
)
? rate of cooling at steady temperature (
o
C/s)
d ? thickness of the bad conductor (m)
h ? thickness of the metallic disc (m)
r?radius of the metallic disc (m)
1
? ? steady temperature of the steam chamber (
o
C)
2
? ? steady temperature of the Metallic disc (
o
C)

PROCEDURE:
The thickness of the bad conductor say card board and thickness of the metallic disc are determined
using a screw gauge. The radius of the metallic disc is found using a vernier caliper. The mass of a metallic
disc is also found using a common balance. The readings are tabulated.

FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
2


PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science and fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems and use this knowledge to acquire
higher education.
2. Core competence
To train the students in Engineering Physics so as to apply their knowledge and training to compare,
and to analyze various engineering industrial problems for finding solutions.
3. Breadth
To provide relevant training and experience to bridge the gap between theoretical learning and
practice that enables them to find solutions for the real time problems in industry and to design products.
4. Professionalism
To inculcate professional and effective communication skills, leadership qualities and team spirit for
the students to make them multi-faceted personalities and develop their ability to relate engineering issues
to broader social context.
5. Lifelong learning/ethics
To demonstrate and practice ethical and professional responsibilities in the industry and society by
and large, through commitment and lifelong learning needed for successful professional career.





3


PROGRAMME OUTCOMES (POs)

a) To demonstrate and apply knowledge of Mathematics, Science and Engineering fundamentals in
Engineering physics
b) To determine the Moment of Inertia of given disc and Rigidity modulus of the given wire using
Torsional Pendulum
c) To determine Young?s modulus of a given bar using Non-Uniform bending
d) To utilize laser source and grating to estimate the wave length, particle size of given powder and
Numerical Aperture & acceptance angle of given optical fiber
e) To find the Thermal conductivity of a bad conductor using Lee?s Disc method
f) To Measure the velocity of ultrasonic wave in a liquid and compressibility of the liquid usingultrasonic
Interferometer
g) To determine the wavelength of Hg source using grating and spectrometer
h) To find the thickness of a thin wire using Air- wedge method
i) To participate and succeed in competitive exams and visualize and work on laboratory and
multidisciplinary tasks











4


BS 8161 ? PHYSICSLABORATORY
(Common to all branches of B.E. / B.TechProgrammes)
SYLLABUS


To introduce different experiments to test basic understanding of physics concepts applied in optics, thermal
physics, properties of matter and liquids.

LIST OF EXPERIMENTS: PHYSICS LABORATORY(Any 5 Experiments)
1. Determination of Rigidity modulus ? Torsion pendulum
2. Determination of Young? s modulus by Non uniform bending method
3. (a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
4. Determination of thermal conductivity of a bad conductor ? Lee?s Disc method.
5. Determination of velocity of sound and compressibility of liquid ? Ultrasonic interferometer
6. Determination of wavelength of mercury spectrum ? spectrometer grating
7. Determination of band gap of a semiconductor
8. Determination of thickness of a thin wire ? Air wedge method




Completion of the course, the students will be able to: apply physics principles of optics and thermal physics
to evaluate engineering properties of materials.


COURSE OUTCOMES
COURSE OBJECTIVES
5

BS 8161 ? PHYSICS LABORATORY
CONTENTS

Sl.No. Name of the Experiment (any 5 experiments)
Page
No.
1.
Determination of Rigidity modulus ? Torsion pendulum
6
2.
Determination of Young ?s modulus by Non uniform bending method
12
3.
(a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
18
4.
Determination of thermal conductivity of a bad conductor ? Lee ?s Disc method.
28
5.
Determination of velocity of sound and compressibility of liquid ? Ultrasonic
interferometer
37
6.
Determination of wavelength of mercury spectrum ? spectrometer grating
42
7.
Determination of thickness of a thin wire ? Air wedge method
48
MEASURING INSTRUMENTS
M1 Screw gauge 54
M2 Vernier Calipers 58
M3 Travelling Microscope 62
M4 Spectrometer 66








6

TORSIONAL PENDULUM










7

Expt. No.1 TORSIONAL PENDULUM

AIM:
To determine the moment of inertia of the given disc and hence to determine the rigidity modulus of
the material of the given suspension wire by torsional oscillations
APPARATUS REQUIRED:
Torsional pendulum, two equal masses, stop clock, screw gauge and meter scale

FORMULA:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
where
m ?mass of the cylinder placed on the disc (kg)
To ?period of the pendulum for a length of l without mass (s)
T1?period of the pendulum for the same length when mass m is placed at a distance d 1
from the center of the suspension wire (s)
T2?period of the pendulum for the same length when mass m is placed at a distance d 2
from the center of the suspension wire (s)
a ? radius of the suspension wire (m)




8

1. To determine the time period of the disc:
Length of the wire (l)= --------
2
10
?
? m
Position of the equal
masses
Time for 10 oscillations Time period
(one oscillation)
s
Trial-1
s
Trial-2
s
Mean
s
Without any masses T0
With masses at
d1 = x10
-2
m
T1
With masses at
d2 = x10
-2
m
T2

2. To determine the radius of the wire:
Least count =0 .01 mm. Zero Error ZE = --------- divisions
Zero Correction ZC = ---------- mm

Sl.No.
Pitch Scale
Reading
PSR
3
10
?
? m
Head Scale
Coincidence
HSC
div
Observed reading
OR = PSR + (HSCXLC)
3
10
?
? m
Correct reading
CR = OR ? ZC
3
10
?
? m




Mean = ----------------
3
10
?
? m



9

PROCEDURE:
Torsional pendulum is suspended from vertical chuck. The length of the suspension wire is measured
between the vertical chuck and the chuck attached to the uniform circular disc (i). The circular disc is twisted
slightly without masses on the disc. Now it executes torsional oscillations. Care is taken to see that the disc
oscillates without wobbling. Time taken for 20 oscillations is noted with the help of a stop clock. Two trials are
taken. The average of these two trial readings is calculated from which the period of oscillations is found out
as T0.
Two identical cylindrical masses each of mass m are symmetrically placed on the disc on either side
of the wire at a distance d from the center of the disc. As before the disc is gently twisted. Time taken for 20
oscillations is noted from which the period of oscillation is calculated as T1.
The cylindrical masses are placed at a distance d2 from the center and the experiment is repeated.
The mean time period of oscillations is calculated T2.
The diameter of the specimen wire is measured accurately with the help of the screw gauge, at
various places on the wire. The average diameter and hence the radius of the wire is calculated as r.
Moment of inertia and the rigidity modulus are determined by the substituting the value of m, T 0, T1, T2,
T3, and l in the formula.










10

CALCULATION:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2

Mass of cylindrical mass, m = ----------- ? 10
-3
kg
Closest distance of the mass from the centre of the suspension wire, d1 = ------------ ? 10
-2
m
Farthest distance of the mass from the centre of suspension wire, d2= ------------? 10
-2
m
Period of oscillation without mass, To = ------------- s
Period of oscillation with mass at d1, T1= ------------ s
Period of oscillation with mass at d2, T2 = ------------- s

Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
= --------------- kg m
2
= --------------- kg m
2

Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
Moment of inertia, I = ------------------ kg m
2
Length of the wire, l = ------------------- ? 10
-2
m
Time of oscillation, To = ------------------ s
Radius of the wire, a = ------------------- ? 10
-3
m
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
= ----------------------
Rigidity modulus, n = ------------------- Nm
-2
11









RESULT:
(i)
The moment of inertia of the given circular disc, I = --------------- kg m
2
(ii)
The rigidity modulus of the material of the given wire, n = -------------- Nm
-2




1. State Hooke?s law.
2. Define ?Rigidity modulus
3. Define ?Moment of inertia
4. What is meant by torsional oscillation?
5. What is period of oscillation?
6. What is meant by twisting couple?
7. Define ? Shearing stress
8. Define ? Shearing strain
9. What is the unit of rigidity modulus?
10. What are the applications of torsional pendulum?


Viva ? voce
12


Young?s Modulus ? Non Uniform Bending
To determine depression (y):
L.C =.001cm M = ___________
3
10
?
? kg

Sl.No

Load


3
10
?
?
k
g
Microscope reading
Mean

2
10
?
? m
Depression
y for M kg

2
10
?
? m
Loading Unloading
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
1 W
2 W+50
3 W+100
4 W+150
5 W+200
6 W+250

Mean (y) = ----------
2
10
?
? m





13

Expt. No.2 YOUNG?S MODULUS BY NON ? UNIFORM BENDING
AIM:
To determine the young?s modulus of the material of the given bar, by non-uniform bending method
APPARATUS REQUIRED:
Travelling microscope, wooden bar, knife- edge, weights hanger, slotted weight, vernier calipers,
screw gauge and pin
FORMULA:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Where,
g ? acceleration due to gravity (9.8 ms
-2
)
l ? length of the bar between two knife edges (m)
b ? breadth of the bar (m)
d ? thickness of the bar (m)
y ? depressiont in the scale reading due to the change of mass M (m)
PROCEDURE:
The given wooden bar, for which young?s modulus is to be determined, is paced symmetrically on the
two knife edges. The distance between the knife edges is measured as the length of the bar (l). It is adjusted
to be, say, 60 cm. the weight hanger is suspended at the centre of the bar. A pin is held vertically at the
centre of the bar with the help of wax.
The given bar is brought to elastic mood by loading and unloading the bar with slotted weights in steps
of 50 g. This is repeated for two or three times. With the hanger as dead load W, the microscope is focused on
to the tip of the pin. The tangential screw of the microscope is adjusted so that the image of the tip of the pin
just touches the horizontal cross wire of the eyepiece. The main scale reading and the vernier scale
coincidence corresponding to this position are noted.
14

To find the breadth using vernier calipers, b:
Least count = ---------- cm Zero error = --------- div.
= ---------- ?10
-2
m Zero correction = ?ZE ?LC= --------- ?10
-2
m
Sl. No.

MSR
x 10
-2
m

VSC
div.
Observed reading
OR = MSR+(VSC ? LC)
x 10
-2
m
Correct Reading
CR = OR ? ZC
x 10
-2
m
1.

2.

3.


Mean, b = ------------------------?10
-2
m
To find the thickness using screw gauge, d:
Least count = ---------- mm Zero error = --------- div.
= ---------- ?10
-3
m Zero correction =ZE ?LC= --------- ?10
-3
m
Sl. No.

PSR
x 10
-3
m

HSC
div.
Observed reading
OR = PSR+ (HSC ? LC)
x 10
-3
m
Correct Reading
CR = OR ? ZC
x 10
-3
m
1.

2.

3.


Mean, d = ---------------------------?10
-3
m
15


The experiment is repeated by adding weights in steps of 50 g and every time the microscope is
adjusted for coincidence. The corresponding readings are noted. The experiment is repeated by unloading the
weights in steps of 50 g and the corresponding readings are tabulated. From this table, the shift in the scale
reading, say y, for a change of mass M is found out.
The breadth of the bar is measured at various points with the help of vernier calipers. Similarly the
thickness of the bar is measured by screw gauge. Substituting the values of M, y, l, d, b and g in the formula,
the young?s modulus of the material of the given bar is calculated.

















16

CALCULATION:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Acceleration due to gravity, g = 9.8 ms
-2
Length of the bar between two knife edges, l = ------------ ?10
-2
m
Breadth of the bar, b = ----------- ?10
-2
m
Thickness of the bar, d = ----------- ?10
-3
m
y = -----------?10
-2
m
E =
???? ?? 2
4?? ?? 3
?? Nm
-2

= ---------------
Young?s modulus, E = ----------- Nm
-2












17








RESULT:
Young?s modulus of the material of the given bar, E = ---------- Nm
-2


1. Define ? Young?s modulus
2. What is meant by Non-uniform bending?
3. Define ? Stress and strain
4. State Hooke?s law.
5. Define ? Neutral axis
6. What is the SI unit of young?s modulus?
7. Define ? Elastic limit
8. Define ? Elasticity
9. What are the factors affecting elasticity?
10. Define ? Elastic fatigue

Viva ? voce
18


To find the wavelength of the laser beam, ?:
Distance between the screen and the grating, D = ------------?10
-2
m
Number of lines per meter length of the grating, N = --------------- Lines per meter
Sl. No.
Order of diffraction,
(m)
Reading of the diffracted image
(?10
-2
m)
?? ?? = ?????? ?1
(
?? ?? ?? )
(deg.)
? =
?????? ?? ?? ????
m

Left side
(xi)
Right side
(xr)
Mean
(xm)










Mean, ? = ---------------- m


19

Expt. No.3(a) WAVELENGTH OF LASER LIGHT AND PARTICLE SIZE


AIM:
(i) To determine the wavelength of the given laser light.
(ii) To determine size of the given particle.
APPARATUS REQUIRED:
Diode laser, grating, screen, given micro particles, scale and screen.
FORMULAE:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
(ii) Grain size or diameter of the grain, 2d =
?????? ?? ?? m
Where
?? ?? ?angle of diffraction (deg.)
M ?order of diffraction (No unit)
N ?number of lines per metre length of the grating (m
-3
)
n ? order of diffraction (no unit)
? ? wavelength of laser light used (m)
D ? distance between the glass plate and the screen (m)
?? ?? - distance between the central bright spot and the nth fringe (m)
PROCEDURE:
TO FIND THE WAVELENGTH OF THE GIVEN LASER LIGHT:
The laser source, grating and screen are placed properly as shown in figure. The diode laser is kept
horizontally and switched on. Extreme care should be taken to avoid direct exposure of laser light on eyes.
20











21

The grating is held normal to the laser beam by adjusting the grating in such a way that the reflected
laser beam from the grating coincides with incident laser beam. Now the diffracted laser spots of various
orders can be seen on the screen, placed on the other side of the grating.

The distance of the different orders on either side of the central spot are measured as x randxi and are
tabulated.The mean value of xrandxiare calculated as xm for the m
th
order diffracted light. The distance
between the grating and the screen is measured as D. Hence, the angle of diffraction for the m
th
order,
?? ?? = ?????? ?1
(
?? ?? ?? )
The experiment is repeated for different orders and the readings are tabulated. From the table, ? for
each order is calculated. Substituting the value of ?, the corresponding order of diffraction and the number of
lines per meter length of the grating, the wavelength is calculated.

TO FIND THE SIZE OF THE GIVEN MICRO PARTICLE:

The lycopodium powder having fine micro particles of nearly same size is sprinkled on a glass plate.
This glass plate is kept between laser source and screen.
Now the particles present in the glass plate diffract laser beam from the source. By adjusting the
distance between the glass plate and the screen, a circular fringe pattern is obtained on the screen with
different orders of fingers. Now distance between the screen and the glass plate (D) is measured.
The distance of the first order and the second order fringe from the centre of spot are also measured.
Using the formula, the particle size is found out. The experiment is repeated for different D values.
22

To find the size of the particle:

CALCULATION:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
Number of lines per metre in the grating, N = ------------ lines per metre.
First order, m1; ?? 1
= ------------
Wavelength, ? =
?????? ?? 1
????
= ------------
Second order, m2; ?? 2
= ------------
Wavelength, ? =
?????? ?? 2
????
= ------------
Third order, m3; ?? 3
= ------------
Wavelength, ? =
?????? ?? 3
????
= ------------
Fourth order, m4; ?? 4
= ------------
Wavelength, ? =
?????? ?? 4
????
= -------------
Fifth order, m5; ?? 5
= ------------

Sl.No



Distance between
screen and glass
plate(D)
2
10
?
? m
Order of
diffraction
(n)
Distance between the
central bright spot and n
th

fringe (xn )
2
10
?
? m
Particle size
2
n
nD
d
x
?
?
m






23

Wavelength, ? =
?????? ?? 4
????
= ------------
Mean wavelength of the given laser light, ? = -------------- m
(ii) Grain size or diameter of the grain. 2d =
?????? ?? ??
Order of differaction, n = --------------
Wavelength of laser light used, ? = ------------- m
Distance between glass plate and the screen, D = ------------ m
Distance between central bright spot and the n
th
fringe,?? ?? = ------------ m
2d =
?????? ?? ??
=
= ------------ m








RESULT:
(i) Wavelength of the laser beam, ? = -------------- m
(ii) Average size of the particle = --------------- m

24


Optical fiber

To find numerical aperture, NA:

Sl. No.
Diameter of the circular patch
D(m)
Distance between the tip of the
fiber and the screen X (m)
NA =
?? (4?? 2
+?? 2
)
1
2





Mean NA =
Therefore, the acceptance angle, ? = Sin
-1
(NA) = -------------------
= -------------------


25

Expt. No.3(b) NUMERICAL APERTURE AND ACCEPTANCE ANGLE
AIM:
To measure the numerical aperture and the acceptance angle of the given fiber cable
APPARATUS REQUIRED:
Optical fiber cable with source, NA jig and in-line adaptor
FORMULA:
The numerical aperture, NA =
?? (4?? 2
+?? 2
)
1
2

Acceptance angle, ? = Sin
-1
(NA)
where,
D ? diameter of the circular patch (m)
X ? distance between the tip of the fiber and the screen (m)
PROCEDURE:
One end of the one metre fiber cable is connected to the laser light source and the other end
to the NA jig as shown in figure. The AC main is plugged in and the laser light is adjusted so that it appears at
the end of the fiber on the NA jig, the intensity knob is adjusted to get maximum intensity.
The white screen with the four concentric circles (10 mm, 20 mm, 30 mm and 40 mm diameter) is held
vertically at a suitable distance to make the red spot from the emitting fiber coincides with the 10 mm circle,
the diameter (D) of the spot is noted. The distance (X) of the screen from the fiber end is recorded.
The procedure is repeated for 20 mm, 30 mm, 40 mm diameter circles and the readings are tabulated.




26

















RESULT:
The numerical aperture, NA = ----------------
Acceptance angle, ? = ----------------




27




1. What is semiconductor diode laser?
2. What is meant by active material in laser?
3. What is meant by LASER?
4. What is stimulated emission?
5. What are the characteristics of laser radiation?
6. What is homo?junction laser?
7. What is hetero?junction laser?
8. What are the applications of semiconductor laser?
9. What are the conditions required for laser action?
10. Define ? Numerical aperture







Viva ? voce
28


Lee?s disc setup


29

Expt. No. 4 THERMAL CONDUCTIVITY OF A BAD CONDUCTOR
BY LEE?S DISC METHOD

AIM:
To determine the coefficient of thermal conductivity of a bad conductor
APPARATUS REQUIRED:
Lee?s disc apparatus, bad conductors, stop-clock, thermometers, screw gauge, vernier calipers and
steam boiler
FORMULA:
Thermal conductivity of a bad conductor,
? ?
? ? ? ?
1 1
2 1
2
2 2
2
? ?
? ?
?
?
?
?
?
?
?
?
?
? k Wm
h r r
h r d
dt
d
MS
K
? ? ?
?

M ? Mass of the metallic disc (Kg)
S ? Specific heat capacity of the metallic disc ( J Kg
-1
K
-1
)
? rate of cooling at steady temperature (
o
C/s)
d ? thickness of the bad conductor (m)
h ? thickness of the metallic disc (m)
r?radius of the metallic disc (m)
1
? ? steady temperature of the steam chamber (
o
C)
2
? ? steady temperature of the Metallic disc (
o
C)

PROCEDURE:
The thickness of the bad conductor say card board and thickness of the metallic disc are determined
using a screw gauge. The radius of the metallic disc is found using a vernier caliper. The mass of a metallic
disc is also found using a common balance. The readings are tabulated.

30

To find the radius of the metallic disc (r) using Vernier Calipers
Least count = 0.01cm Zero error = ? ???div
Zero correction = ? ???cm
= --------- ?10
-2
m
Sl.No.
MSR
(x10
-2
m)
VSC
(div.)
OR = MSR +(VSC x LC)
(x10
-2
m)
CR = OR ? ZC
(x10
-2
m)
1
2
3
4

Mean radius, r = --------------------------------- x10
-2
m
To find the thickness of the bad conductor (d) using Screw gauge
Least count = 0.01mm Zero error = ? ???div
Zero correction = ? ???mm
Sl.No.
PSR
(x10
-3
m)
HSC
(div.)
OR = PSR + (HSC x LC)
(x10
-3
m)
CR = OR ? ZC
(x10
-3
m)
1.
2.
3.
4.

Mean, d = -------------------------------- x10
-3
m
FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
2


PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science and fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems and use this knowledge to acquire
higher education.
2. Core competence
To train the students in Engineering Physics so as to apply their knowledge and training to compare,
and to analyze various engineering industrial problems for finding solutions.
3. Breadth
To provide relevant training and experience to bridge the gap between theoretical learning and
practice that enables them to find solutions for the real time problems in industry and to design products.
4. Professionalism
To inculcate professional and effective communication skills, leadership qualities and team spirit for
the students to make them multi-faceted personalities and develop their ability to relate engineering issues
to broader social context.
5. Lifelong learning/ethics
To demonstrate and practice ethical and professional responsibilities in the industry and society by
and large, through commitment and lifelong learning needed for successful professional career.





3


PROGRAMME OUTCOMES (POs)

a) To demonstrate and apply knowledge of Mathematics, Science and Engineering fundamentals in
Engineering physics
b) To determine the Moment of Inertia of given disc and Rigidity modulus of the given wire using
Torsional Pendulum
c) To determine Young?s modulus of a given bar using Non-Uniform bending
d) To utilize laser source and grating to estimate the wave length, particle size of given powder and
Numerical Aperture & acceptance angle of given optical fiber
e) To find the Thermal conductivity of a bad conductor using Lee?s Disc method
f) To Measure the velocity of ultrasonic wave in a liquid and compressibility of the liquid usingultrasonic
Interferometer
g) To determine the wavelength of Hg source using grating and spectrometer
h) To find the thickness of a thin wire using Air- wedge method
i) To participate and succeed in competitive exams and visualize and work on laboratory and
multidisciplinary tasks











4


BS 8161 ? PHYSICSLABORATORY
(Common to all branches of B.E. / B.TechProgrammes)
SYLLABUS


To introduce different experiments to test basic understanding of physics concepts applied in optics, thermal
physics, properties of matter and liquids.

LIST OF EXPERIMENTS: PHYSICS LABORATORY(Any 5 Experiments)
1. Determination of Rigidity modulus ? Torsion pendulum
2. Determination of Young? s modulus by Non uniform bending method
3. (a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
4. Determination of thermal conductivity of a bad conductor ? Lee?s Disc method.
5. Determination of velocity of sound and compressibility of liquid ? Ultrasonic interferometer
6. Determination of wavelength of mercury spectrum ? spectrometer grating
7. Determination of band gap of a semiconductor
8. Determination of thickness of a thin wire ? Air wedge method




Completion of the course, the students will be able to: apply physics principles of optics and thermal physics
to evaluate engineering properties of materials.


COURSE OUTCOMES
COURSE OBJECTIVES
5

BS 8161 ? PHYSICS LABORATORY
CONTENTS

Sl.No. Name of the Experiment (any 5 experiments)
Page
No.
1.
Determination of Rigidity modulus ? Torsion pendulum
6
2.
Determination of Young ?s modulus by Non uniform bending method
12
3.
(a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
18
4.
Determination of thermal conductivity of a bad conductor ? Lee ?s Disc method.
28
5.
Determination of velocity of sound and compressibility of liquid ? Ultrasonic
interferometer
37
6.
Determination of wavelength of mercury spectrum ? spectrometer grating
42
7.
Determination of thickness of a thin wire ? Air wedge method
48
MEASURING INSTRUMENTS
M1 Screw gauge 54
M2 Vernier Calipers 58
M3 Travelling Microscope 62
M4 Spectrometer 66








6

TORSIONAL PENDULUM










7

Expt. No.1 TORSIONAL PENDULUM

AIM:
To determine the moment of inertia of the given disc and hence to determine the rigidity modulus of
the material of the given suspension wire by torsional oscillations
APPARATUS REQUIRED:
Torsional pendulum, two equal masses, stop clock, screw gauge and meter scale

FORMULA:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
where
m ?mass of the cylinder placed on the disc (kg)
To ?period of the pendulum for a length of l without mass (s)
T1?period of the pendulum for the same length when mass m is placed at a distance d 1
from the center of the suspension wire (s)
T2?period of the pendulum for the same length when mass m is placed at a distance d 2
from the center of the suspension wire (s)
a ? radius of the suspension wire (m)




8

1. To determine the time period of the disc:
Length of the wire (l)= --------
2
10
?
? m
Position of the equal
masses
Time for 10 oscillations Time period
(one oscillation)
s
Trial-1
s
Trial-2
s
Mean
s
Without any masses T0
With masses at
d1 = x10
-2
m
T1
With masses at
d2 = x10
-2
m
T2

2. To determine the radius of the wire:
Least count =0 .01 mm. Zero Error ZE = --------- divisions
Zero Correction ZC = ---------- mm

Sl.No.
Pitch Scale
Reading
PSR
3
10
?
? m
Head Scale
Coincidence
HSC
div
Observed reading
OR = PSR + (HSCXLC)
3
10
?
? m
Correct reading
CR = OR ? ZC
3
10
?
? m




Mean = ----------------
3
10
?
? m



9

PROCEDURE:
Torsional pendulum is suspended from vertical chuck. The length of the suspension wire is measured
between the vertical chuck and the chuck attached to the uniform circular disc (i). The circular disc is twisted
slightly without masses on the disc. Now it executes torsional oscillations. Care is taken to see that the disc
oscillates without wobbling. Time taken for 20 oscillations is noted with the help of a stop clock. Two trials are
taken. The average of these two trial readings is calculated from which the period of oscillations is found out
as T0.
Two identical cylindrical masses each of mass m are symmetrically placed on the disc on either side
of the wire at a distance d from the center of the disc. As before the disc is gently twisted. Time taken for 20
oscillations is noted from which the period of oscillation is calculated as T1.
The cylindrical masses are placed at a distance d2 from the center and the experiment is repeated.
The mean time period of oscillations is calculated T2.
The diameter of the specimen wire is measured accurately with the help of the screw gauge, at
various places on the wire. The average diameter and hence the radius of the wire is calculated as r.
Moment of inertia and the rigidity modulus are determined by the substituting the value of m, T 0, T1, T2,
T3, and l in the formula.










10

CALCULATION:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2

Mass of cylindrical mass, m = ----------- ? 10
-3
kg
Closest distance of the mass from the centre of the suspension wire, d1 = ------------ ? 10
-2
m
Farthest distance of the mass from the centre of suspension wire, d2= ------------? 10
-2
m
Period of oscillation without mass, To = ------------- s
Period of oscillation with mass at d1, T1= ------------ s
Period of oscillation with mass at d2, T2 = ------------- s

Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
= --------------- kg m
2
= --------------- kg m
2

Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
Moment of inertia, I = ------------------ kg m
2
Length of the wire, l = ------------------- ? 10
-2
m
Time of oscillation, To = ------------------ s
Radius of the wire, a = ------------------- ? 10
-3
m
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
= ----------------------
Rigidity modulus, n = ------------------- Nm
-2
11









RESULT:
(i)
The moment of inertia of the given circular disc, I = --------------- kg m
2
(ii)
The rigidity modulus of the material of the given wire, n = -------------- Nm
-2




1. State Hooke?s law.
2. Define ?Rigidity modulus
3. Define ?Moment of inertia
4. What is meant by torsional oscillation?
5. What is period of oscillation?
6. What is meant by twisting couple?
7. Define ? Shearing stress
8. Define ? Shearing strain
9. What is the unit of rigidity modulus?
10. What are the applications of torsional pendulum?


Viva ? voce
12


Young?s Modulus ? Non Uniform Bending
To determine depression (y):
L.C =.001cm M = ___________
3
10
?
? kg

Sl.No

Load


3
10
?
?
k
g
Microscope reading
Mean

2
10
?
? m
Depression
y for M kg

2
10
?
? m
Loading Unloading
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
1 W
2 W+50
3 W+100
4 W+150
5 W+200
6 W+250

Mean (y) = ----------
2
10
?
? m





13

Expt. No.2 YOUNG?S MODULUS BY NON ? UNIFORM BENDING
AIM:
To determine the young?s modulus of the material of the given bar, by non-uniform bending method
APPARATUS REQUIRED:
Travelling microscope, wooden bar, knife- edge, weights hanger, slotted weight, vernier calipers,
screw gauge and pin
FORMULA:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Where,
g ? acceleration due to gravity (9.8 ms
-2
)
l ? length of the bar between two knife edges (m)
b ? breadth of the bar (m)
d ? thickness of the bar (m)
y ? depressiont in the scale reading due to the change of mass M (m)
PROCEDURE:
The given wooden bar, for which young?s modulus is to be determined, is paced symmetrically on the
two knife edges. The distance between the knife edges is measured as the length of the bar (l). It is adjusted
to be, say, 60 cm. the weight hanger is suspended at the centre of the bar. A pin is held vertically at the
centre of the bar with the help of wax.
The given bar is brought to elastic mood by loading and unloading the bar with slotted weights in steps
of 50 g. This is repeated for two or three times. With the hanger as dead load W, the microscope is focused on
to the tip of the pin. The tangential screw of the microscope is adjusted so that the image of the tip of the pin
just touches the horizontal cross wire of the eyepiece. The main scale reading and the vernier scale
coincidence corresponding to this position are noted.
14

To find the breadth using vernier calipers, b:
Least count = ---------- cm Zero error = --------- div.
= ---------- ?10
-2
m Zero correction = ?ZE ?LC= --------- ?10
-2
m
Sl. No.

MSR
x 10
-2
m

VSC
div.
Observed reading
OR = MSR+(VSC ? LC)
x 10
-2
m
Correct Reading
CR = OR ? ZC
x 10
-2
m
1.

2.

3.


Mean, b = ------------------------?10
-2
m
To find the thickness using screw gauge, d:
Least count = ---------- mm Zero error = --------- div.
= ---------- ?10
-3
m Zero correction =ZE ?LC= --------- ?10
-3
m
Sl. No.

PSR
x 10
-3
m

HSC
div.
Observed reading
OR = PSR+ (HSC ? LC)
x 10
-3
m
Correct Reading
CR = OR ? ZC
x 10
-3
m
1.

2.

3.


Mean, d = ---------------------------?10
-3
m
15


The experiment is repeated by adding weights in steps of 50 g and every time the microscope is
adjusted for coincidence. The corresponding readings are noted. The experiment is repeated by unloading the
weights in steps of 50 g and the corresponding readings are tabulated. From this table, the shift in the scale
reading, say y, for a change of mass M is found out.
The breadth of the bar is measured at various points with the help of vernier calipers. Similarly the
thickness of the bar is measured by screw gauge. Substituting the values of M, y, l, d, b and g in the formula,
the young?s modulus of the material of the given bar is calculated.

















16

CALCULATION:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Acceleration due to gravity, g = 9.8 ms
-2
Length of the bar between two knife edges, l = ------------ ?10
-2
m
Breadth of the bar, b = ----------- ?10
-2
m
Thickness of the bar, d = ----------- ?10
-3
m
y = -----------?10
-2
m
E =
???? ?? 2
4?? ?? 3
?? Nm
-2

= ---------------
Young?s modulus, E = ----------- Nm
-2












17








RESULT:
Young?s modulus of the material of the given bar, E = ---------- Nm
-2


1. Define ? Young?s modulus
2. What is meant by Non-uniform bending?
3. Define ? Stress and strain
4. State Hooke?s law.
5. Define ? Neutral axis
6. What is the SI unit of young?s modulus?
7. Define ? Elastic limit
8. Define ? Elasticity
9. What are the factors affecting elasticity?
10. Define ? Elastic fatigue

Viva ? voce
18


To find the wavelength of the laser beam, ?:
Distance between the screen and the grating, D = ------------?10
-2
m
Number of lines per meter length of the grating, N = --------------- Lines per meter
Sl. No.
Order of diffraction,
(m)
Reading of the diffracted image
(?10
-2
m)
?? ?? = ?????? ?1
(
?? ?? ?? )
(deg.)
? =
?????? ?? ?? ????
m

Left side
(xi)
Right side
(xr)
Mean
(xm)










Mean, ? = ---------------- m


19

Expt. No.3(a) WAVELENGTH OF LASER LIGHT AND PARTICLE SIZE


AIM:
(i) To determine the wavelength of the given laser light.
(ii) To determine size of the given particle.
APPARATUS REQUIRED:
Diode laser, grating, screen, given micro particles, scale and screen.
FORMULAE:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
(ii) Grain size or diameter of the grain, 2d =
?????? ?? ?? m
Where
?? ?? ?angle of diffraction (deg.)
M ?order of diffraction (No unit)
N ?number of lines per metre length of the grating (m
-3
)
n ? order of diffraction (no unit)
? ? wavelength of laser light used (m)
D ? distance between the glass plate and the screen (m)
?? ?? - distance between the central bright spot and the nth fringe (m)
PROCEDURE:
TO FIND THE WAVELENGTH OF THE GIVEN LASER LIGHT:
The laser source, grating and screen are placed properly as shown in figure. The diode laser is kept
horizontally and switched on. Extreme care should be taken to avoid direct exposure of laser light on eyes.
20











21

The grating is held normal to the laser beam by adjusting the grating in such a way that the reflected
laser beam from the grating coincides with incident laser beam. Now the diffracted laser spots of various
orders can be seen on the screen, placed on the other side of the grating.

The distance of the different orders on either side of the central spot are measured as x randxi and are
tabulated.The mean value of xrandxiare calculated as xm for the m
th
order diffracted light. The distance
between the grating and the screen is measured as D. Hence, the angle of diffraction for the m
th
order,
?? ?? = ?????? ?1
(
?? ?? ?? )
The experiment is repeated for different orders and the readings are tabulated. From the table, ? for
each order is calculated. Substituting the value of ?, the corresponding order of diffraction and the number of
lines per meter length of the grating, the wavelength is calculated.

TO FIND THE SIZE OF THE GIVEN MICRO PARTICLE:

The lycopodium powder having fine micro particles of nearly same size is sprinkled on a glass plate.
This glass plate is kept between laser source and screen.
Now the particles present in the glass plate diffract laser beam from the source. By adjusting the
distance between the glass plate and the screen, a circular fringe pattern is obtained on the screen with
different orders of fingers. Now distance between the screen and the glass plate (D) is measured.
The distance of the first order and the second order fringe from the centre of spot are also measured.
Using the formula, the particle size is found out. The experiment is repeated for different D values.
22

To find the size of the particle:

CALCULATION:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
Number of lines per metre in the grating, N = ------------ lines per metre.
First order, m1; ?? 1
= ------------
Wavelength, ? =
?????? ?? 1
????
= ------------
Second order, m2; ?? 2
= ------------
Wavelength, ? =
?????? ?? 2
????
= ------------
Third order, m3; ?? 3
= ------------
Wavelength, ? =
?????? ?? 3
????
= ------------
Fourth order, m4; ?? 4
= ------------
Wavelength, ? =
?????? ?? 4
????
= -------------
Fifth order, m5; ?? 5
= ------------

Sl.No



Distance between
screen and glass
plate(D)
2
10
?
? m
Order of
diffraction
(n)
Distance between the
central bright spot and n
th

fringe (xn )
2
10
?
? m
Particle size
2
n
nD
d
x
?
?
m






23

Wavelength, ? =
?????? ?? 4
????
= ------------
Mean wavelength of the given laser light, ? = -------------- m
(ii) Grain size or diameter of the grain. 2d =
?????? ?? ??
Order of differaction, n = --------------
Wavelength of laser light used, ? = ------------- m
Distance between glass plate and the screen, D = ------------ m
Distance between central bright spot and the n
th
fringe,?? ?? = ------------ m
2d =
?????? ?? ??
=
= ------------ m








RESULT:
(i) Wavelength of the laser beam, ? = -------------- m
(ii) Average size of the particle = --------------- m

24


Optical fiber

To find numerical aperture, NA:

Sl. No.
Diameter of the circular patch
D(m)
Distance between the tip of the
fiber and the screen X (m)
NA =
?? (4?? 2
+?? 2
)
1
2





Mean NA =
Therefore, the acceptance angle, ? = Sin
-1
(NA) = -------------------
= -------------------


25

Expt. No.3(b) NUMERICAL APERTURE AND ACCEPTANCE ANGLE
AIM:
To measure the numerical aperture and the acceptance angle of the given fiber cable
APPARATUS REQUIRED:
Optical fiber cable with source, NA jig and in-line adaptor
FORMULA:
The numerical aperture, NA =
?? (4?? 2
+?? 2
)
1
2

Acceptance angle, ? = Sin
-1
(NA)
where,
D ? diameter of the circular patch (m)
X ? distance between the tip of the fiber and the screen (m)
PROCEDURE:
One end of the one metre fiber cable is connected to the laser light source and the other end
to the NA jig as shown in figure. The AC main is plugged in and the laser light is adjusted so that it appears at
the end of the fiber on the NA jig, the intensity knob is adjusted to get maximum intensity.
The white screen with the four concentric circles (10 mm, 20 mm, 30 mm and 40 mm diameter) is held
vertically at a suitable distance to make the red spot from the emitting fiber coincides with the 10 mm circle,
the diameter (D) of the spot is noted. The distance (X) of the screen from the fiber end is recorded.
The procedure is repeated for 20 mm, 30 mm, 40 mm diameter circles and the readings are tabulated.




26

















RESULT:
The numerical aperture, NA = ----------------
Acceptance angle, ? = ----------------




27




1. What is semiconductor diode laser?
2. What is meant by active material in laser?
3. What is meant by LASER?
4. What is stimulated emission?
5. What are the characteristics of laser radiation?
6. What is homo?junction laser?
7. What is hetero?junction laser?
8. What are the applications of semiconductor laser?
9. What are the conditions required for laser action?
10. Define ? Numerical aperture







Viva ? voce
28


Lee?s disc setup


29

Expt. No. 4 THERMAL CONDUCTIVITY OF A BAD CONDUCTOR
BY LEE?S DISC METHOD

AIM:
To determine the coefficient of thermal conductivity of a bad conductor
APPARATUS REQUIRED:
Lee?s disc apparatus, bad conductors, stop-clock, thermometers, screw gauge, vernier calipers and
steam boiler
FORMULA:
Thermal conductivity of a bad conductor,
? ?
? ? ? ?
1 1
2 1
2
2 2
2
? ?
? ?
?
?
?
?
?
?
?
?
?
? k Wm
h r r
h r d
dt
d
MS
K
? ? ?
?

M ? Mass of the metallic disc (Kg)
S ? Specific heat capacity of the metallic disc ( J Kg
-1
K
-1
)
? rate of cooling at steady temperature (
o
C/s)
d ? thickness of the bad conductor (m)
h ? thickness of the metallic disc (m)
r?radius of the metallic disc (m)
1
? ? steady temperature of the steam chamber (
o
C)
2
? ? steady temperature of the Metallic disc (
o
C)

PROCEDURE:
The thickness of the bad conductor say card board and thickness of the metallic disc are determined
using a screw gauge. The radius of the metallic disc is found using a vernier caliper. The mass of a metallic
disc is also found using a common balance. The readings are tabulated.

30

To find the radius of the metallic disc (r) using Vernier Calipers
Least count = 0.01cm Zero error = ? ???div
Zero correction = ? ???cm
= --------- ?10
-2
m
Sl.No.
MSR
(x10
-2
m)
VSC
(div.)
OR = MSR +(VSC x LC)
(x10
-2
m)
CR = OR ? ZC
(x10
-2
m)
1
2
3
4

Mean radius, r = --------------------------------- x10
-2
m
To find the thickness of the bad conductor (d) using Screw gauge
Least count = 0.01mm Zero error = ? ???div
Zero correction = ? ???mm
Sl.No.
PSR
(x10
-3
m)
HSC
(div.)
OR = PSR + (HSC x LC)
(x10
-3
m)
CR = OR ? ZC
(x10
-3
m)
1.
2.
3.
4.

Mean, d = -------------------------------- x10
-3
m
31

The whole Lee?s disc apparatus is suspended from a stand as shown in the figure. The given bad
conductor is placed in between the metallic disc and the steam chamber. Two thermometers T1 and T2 are
inserted into the respective holes.
Steam from the steam boiler is passed into the steam chamber until the temperature of the steam
chamber and the metallic disc are steady. The Steady temperature (?1) of the steam chamber and (?2) of the
metallic disc recorded by the thermometers are noted.
Now the bad conductor is removed and the steam chamber is placed in direct contact with the metallic
disc. The temperature of the disc rapidly rises. When the temperature of the disc rises about 10
o
Cabove
?2
o
C, the steam chamber is carefully removed after cutting of the steam supply.
When the temperature of the disc reaches 10
o
C above the steady temperature of the disc i.e. (?2+
10)
o
C , stop clock is started. Time for every one degree celsius fall of temperature is noted until the metallic
disc attains a temperature (?2 - 10)
o
C.
A graph is drawn taking time along the x-axis and temperature along the y-axis. The cooling curve is
obtained .To obtain the rate of the cooling (
????
????
)
?? 2
from this graph, a triangle is drawn by taking 1
o
C above
and 1
o
Cbelow the steady temperature ?2. Then the slope AB / BC gives the rate of cooling at(
????
????
)
?? 2
. From
these readings and using the given formula thermal conductivity of the given bad conductor is calculated.










FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
2


PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science and fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems and use this knowledge to acquire
higher education.
2. Core competence
To train the students in Engineering Physics so as to apply their knowledge and training to compare,
and to analyze various engineering industrial problems for finding solutions.
3. Breadth
To provide relevant training and experience to bridge the gap between theoretical learning and
practice that enables them to find solutions for the real time problems in industry and to design products.
4. Professionalism
To inculcate professional and effective communication skills, leadership qualities and team spirit for
the students to make them multi-faceted personalities and develop their ability to relate engineering issues
to broader social context.
5. Lifelong learning/ethics
To demonstrate and practice ethical and professional responsibilities in the industry and society by
and large, through commitment and lifelong learning needed for successful professional career.





3


PROGRAMME OUTCOMES (POs)

a) To demonstrate and apply knowledge of Mathematics, Science and Engineering fundamentals in
Engineering physics
b) To determine the Moment of Inertia of given disc and Rigidity modulus of the given wire using
Torsional Pendulum
c) To determine Young?s modulus of a given bar using Non-Uniform bending
d) To utilize laser source and grating to estimate the wave length, particle size of given powder and
Numerical Aperture & acceptance angle of given optical fiber
e) To find the Thermal conductivity of a bad conductor using Lee?s Disc method
f) To Measure the velocity of ultrasonic wave in a liquid and compressibility of the liquid usingultrasonic
Interferometer
g) To determine the wavelength of Hg source using grating and spectrometer
h) To find the thickness of a thin wire using Air- wedge method
i) To participate and succeed in competitive exams and visualize and work on laboratory and
multidisciplinary tasks











4


BS 8161 ? PHYSICSLABORATORY
(Common to all branches of B.E. / B.TechProgrammes)
SYLLABUS


To introduce different experiments to test basic understanding of physics concepts applied in optics, thermal
physics, properties of matter and liquids.

LIST OF EXPERIMENTS: PHYSICS LABORATORY(Any 5 Experiments)
1. Determination of Rigidity modulus ? Torsion pendulum
2. Determination of Young? s modulus by Non uniform bending method
3. (a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
4. Determination of thermal conductivity of a bad conductor ? Lee?s Disc method.
5. Determination of velocity of sound and compressibility of liquid ? Ultrasonic interferometer
6. Determination of wavelength of mercury spectrum ? spectrometer grating
7. Determination of band gap of a semiconductor
8. Determination of thickness of a thin wire ? Air wedge method




Completion of the course, the students will be able to: apply physics principles of optics and thermal physics
to evaluate engineering properties of materials.


COURSE OUTCOMES
COURSE OBJECTIVES
5

BS 8161 ? PHYSICS LABORATORY
CONTENTS

Sl.No. Name of the Experiment (any 5 experiments)
Page
No.
1.
Determination of Rigidity modulus ? Torsion pendulum
6
2.
Determination of Young ?s modulus by Non uniform bending method
12
3.
(a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
18
4.
Determination of thermal conductivity of a bad conductor ? Lee ?s Disc method.
28
5.
Determination of velocity of sound and compressibility of liquid ? Ultrasonic
interferometer
37
6.
Determination of wavelength of mercury spectrum ? spectrometer grating
42
7.
Determination of thickness of a thin wire ? Air wedge method
48
MEASURING INSTRUMENTS
M1 Screw gauge 54
M2 Vernier Calipers 58
M3 Travelling Microscope 62
M4 Spectrometer 66








6

TORSIONAL PENDULUM










7

Expt. No.1 TORSIONAL PENDULUM

AIM:
To determine the moment of inertia of the given disc and hence to determine the rigidity modulus of
the material of the given suspension wire by torsional oscillations
APPARATUS REQUIRED:
Torsional pendulum, two equal masses, stop clock, screw gauge and meter scale

FORMULA:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
where
m ?mass of the cylinder placed on the disc (kg)
To ?period of the pendulum for a length of l without mass (s)
T1?period of the pendulum for the same length when mass m is placed at a distance d 1
from the center of the suspension wire (s)
T2?period of the pendulum for the same length when mass m is placed at a distance d 2
from the center of the suspension wire (s)
a ? radius of the suspension wire (m)




8

1. To determine the time period of the disc:
Length of the wire (l)= --------
2
10
?
? m
Position of the equal
masses
Time for 10 oscillations Time period
(one oscillation)
s
Trial-1
s
Trial-2
s
Mean
s
Without any masses T0
With masses at
d1 = x10
-2
m
T1
With masses at
d2 = x10
-2
m
T2

2. To determine the radius of the wire:
Least count =0 .01 mm. Zero Error ZE = --------- divisions
Zero Correction ZC = ---------- mm

Sl.No.
Pitch Scale
Reading
PSR
3
10
?
? m
Head Scale
Coincidence
HSC
div
Observed reading
OR = PSR + (HSCXLC)
3
10
?
? m
Correct reading
CR = OR ? ZC
3
10
?
? m




Mean = ----------------
3
10
?
? m



9

PROCEDURE:
Torsional pendulum is suspended from vertical chuck. The length of the suspension wire is measured
between the vertical chuck and the chuck attached to the uniform circular disc (i). The circular disc is twisted
slightly without masses on the disc. Now it executes torsional oscillations. Care is taken to see that the disc
oscillates without wobbling. Time taken for 20 oscillations is noted with the help of a stop clock. Two trials are
taken. The average of these two trial readings is calculated from which the period of oscillations is found out
as T0.
Two identical cylindrical masses each of mass m are symmetrically placed on the disc on either side
of the wire at a distance d from the center of the disc. As before the disc is gently twisted. Time taken for 20
oscillations is noted from which the period of oscillation is calculated as T1.
The cylindrical masses are placed at a distance d2 from the center and the experiment is repeated.
The mean time period of oscillations is calculated T2.
The diameter of the specimen wire is measured accurately with the help of the screw gauge, at
various places on the wire. The average diameter and hence the radius of the wire is calculated as r.
Moment of inertia and the rigidity modulus are determined by the substituting the value of m, T 0, T1, T2,
T3, and l in the formula.










10

CALCULATION:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2

Mass of cylindrical mass, m = ----------- ? 10
-3
kg
Closest distance of the mass from the centre of the suspension wire, d1 = ------------ ? 10
-2
m
Farthest distance of the mass from the centre of suspension wire, d2= ------------? 10
-2
m
Period of oscillation without mass, To = ------------- s
Period of oscillation with mass at d1, T1= ------------ s
Period of oscillation with mass at d2, T2 = ------------- s

Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
= --------------- kg m
2
= --------------- kg m
2

Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
Moment of inertia, I = ------------------ kg m
2
Length of the wire, l = ------------------- ? 10
-2
m
Time of oscillation, To = ------------------ s
Radius of the wire, a = ------------------- ? 10
-3
m
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
= ----------------------
Rigidity modulus, n = ------------------- Nm
-2
11









RESULT:
(i)
The moment of inertia of the given circular disc, I = --------------- kg m
2
(ii)
The rigidity modulus of the material of the given wire, n = -------------- Nm
-2




1. State Hooke?s law.
2. Define ?Rigidity modulus
3. Define ?Moment of inertia
4. What is meant by torsional oscillation?
5. What is period of oscillation?
6. What is meant by twisting couple?
7. Define ? Shearing stress
8. Define ? Shearing strain
9. What is the unit of rigidity modulus?
10. What are the applications of torsional pendulum?


Viva ? voce
12


Young?s Modulus ? Non Uniform Bending
To determine depression (y):
L.C =.001cm M = ___________
3
10
?
? kg

Sl.No

Load


3
10
?
?
k
g
Microscope reading
Mean

2
10
?
? m
Depression
y for M kg

2
10
?
? m
Loading Unloading
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
1 W
2 W+50
3 W+100
4 W+150
5 W+200
6 W+250

Mean (y) = ----------
2
10
?
? m





13

Expt. No.2 YOUNG?S MODULUS BY NON ? UNIFORM BENDING
AIM:
To determine the young?s modulus of the material of the given bar, by non-uniform bending method
APPARATUS REQUIRED:
Travelling microscope, wooden bar, knife- edge, weights hanger, slotted weight, vernier calipers,
screw gauge and pin
FORMULA:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Where,
g ? acceleration due to gravity (9.8 ms
-2
)
l ? length of the bar between two knife edges (m)
b ? breadth of the bar (m)
d ? thickness of the bar (m)
y ? depressiont in the scale reading due to the change of mass M (m)
PROCEDURE:
The given wooden bar, for which young?s modulus is to be determined, is paced symmetrically on the
two knife edges. The distance between the knife edges is measured as the length of the bar (l). It is adjusted
to be, say, 60 cm. the weight hanger is suspended at the centre of the bar. A pin is held vertically at the
centre of the bar with the help of wax.
The given bar is brought to elastic mood by loading and unloading the bar with slotted weights in steps
of 50 g. This is repeated for two or three times. With the hanger as dead load W, the microscope is focused on
to the tip of the pin. The tangential screw of the microscope is adjusted so that the image of the tip of the pin
just touches the horizontal cross wire of the eyepiece. The main scale reading and the vernier scale
coincidence corresponding to this position are noted.
14

To find the breadth using vernier calipers, b:
Least count = ---------- cm Zero error = --------- div.
= ---------- ?10
-2
m Zero correction = ?ZE ?LC= --------- ?10
-2
m
Sl. No.

MSR
x 10
-2
m

VSC
div.
Observed reading
OR = MSR+(VSC ? LC)
x 10
-2
m
Correct Reading
CR = OR ? ZC
x 10
-2
m
1.

2.

3.


Mean, b = ------------------------?10
-2
m
To find the thickness using screw gauge, d:
Least count = ---------- mm Zero error = --------- div.
= ---------- ?10
-3
m Zero correction =ZE ?LC= --------- ?10
-3
m
Sl. No.

PSR
x 10
-3
m

HSC
div.
Observed reading
OR = PSR+ (HSC ? LC)
x 10
-3
m
Correct Reading
CR = OR ? ZC
x 10
-3
m
1.

2.

3.


Mean, d = ---------------------------?10
-3
m
15


The experiment is repeated by adding weights in steps of 50 g and every time the microscope is
adjusted for coincidence. The corresponding readings are noted. The experiment is repeated by unloading the
weights in steps of 50 g and the corresponding readings are tabulated. From this table, the shift in the scale
reading, say y, for a change of mass M is found out.
The breadth of the bar is measured at various points with the help of vernier calipers. Similarly the
thickness of the bar is measured by screw gauge. Substituting the values of M, y, l, d, b and g in the formula,
the young?s modulus of the material of the given bar is calculated.

















16

CALCULATION:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Acceleration due to gravity, g = 9.8 ms
-2
Length of the bar between two knife edges, l = ------------ ?10
-2
m
Breadth of the bar, b = ----------- ?10
-2
m
Thickness of the bar, d = ----------- ?10
-3
m
y = -----------?10
-2
m
E =
???? ?? 2
4?? ?? 3
?? Nm
-2

= ---------------
Young?s modulus, E = ----------- Nm
-2












17








RESULT:
Young?s modulus of the material of the given bar, E = ---------- Nm
-2


1. Define ? Young?s modulus
2. What is meant by Non-uniform bending?
3. Define ? Stress and strain
4. State Hooke?s law.
5. Define ? Neutral axis
6. What is the SI unit of young?s modulus?
7. Define ? Elastic limit
8. Define ? Elasticity
9. What are the factors affecting elasticity?
10. Define ? Elastic fatigue

Viva ? voce
18


To find the wavelength of the laser beam, ?:
Distance between the screen and the grating, D = ------------?10
-2
m
Number of lines per meter length of the grating, N = --------------- Lines per meter
Sl. No.
Order of diffraction,
(m)
Reading of the diffracted image
(?10
-2
m)
?? ?? = ?????? ?1
(
?? ?? ?? )
(deg.)
? =
?????? ?? ?? ????
m

Left side
(xi)
Right side
(xr)
Mean
(xm)










Mean, ? = ---------------- m


19

Expt. No.3(a) WAVELENGTH OF LASER LIGHT AND PARTICLE SIZE


AIM:
(i) To determine the wavelength of the given laser light.
(ii) To determine size of the given particle.
APPARATUS REQUIRED:
Diode laser, grating, screen, given micro particles, scale and screen.
FORMULAE:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
(ii) Grain size or diameter of the grain, 2d =
?????? ?? ?? m
Where
?? ?? ?angle of diffraction (deg.)
M ?order of diffraction (No unit)
N ?number of lines per metre length of the grating (m
-3
)
n ? order of diffraction (no unit)
? ? wavelength of laser light used (m)
D ? distance between the glass plate and the screen (m)
?? ?? - distance between the central bright spot and the nth fringe (m)
PROCEDURE:
TO FIND THE WAVELENGTH OF THE GIVEN LASER LIGHT:
The laser source, grating and screen are placed properly as shown in figure. The diode laser is kept
horizontally and switched on. Extreme care should be taken to avoid direct exposure of laser light on eyes.
20











21

The grating is held normal to the laser beam by adjusting the grating in such a way that the reflected
laser beam from the grating coincides with incident laser beam. Now the diffracted laser spots of various
orders can be seen on the screen, placed on the other side of the grating.

The distance of the different orders on either side of the central spot are measured as x randxi and are
tabulated.The mean value of xrandxiare calculated as xm for the m
th
order diffracted light. The distance
between the grating and the screen is measured as D. Hence, the angle of diffraction for the m
th
order,
?? ?? = ?????? ?1
(
?? ?? ?? )
The experiment is repeated for different orders and the readings are tabulated. From the table, ? for
each order is calculated. Substituting the value of ?, the corresponding order of diffraction and the number of
lines per meter length of the grating, the wavelength is calculated.

TO FIND THE SIZE OF THE GIVEN MICRO PARTICLE:

The lycopodium powder having fine micro particles of nearly same size is sprinkled on a glass plate.
This glass plate is kept between laser source and screen.
Now the particles present in the glass plate diffract laser beam from the source. By adjusting the
distance between the glass plate and the screen, a circular fringe pattern is obtained on the screen with
different orders of fingers. Now distance between the screen and the glass plate (D) is measured.
The distance of the first order and the second order fringe from the centre of spot are also measured.
Using the formula, the particle size is found out. The experiment is repeated for different D values.
22

To find the size of the particle:

CALCULATION:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
Number of lines per metre in the grating, N = ------------ lines per metre.
First order, m1; ?? 1
= ------------
Wavelength, ? =
?????? ?? 1
????
= ------------
Second order, m2; ?? 2
= ------------
Wavelength, ? =
?????? ?? 2
????
= ------------
Third order, m3; ?? 3
= ------------
Wavelength, ? =
?????? ?? 3
????
= ------------
Fourth order, m4; ?? 4
= ------------
Wavelength, ? =
?????? ?? 4
????
= -------------
Fifth order, m5; ?? 5
= ------------

Sl.No



Distance between
screen and glass
plate(D)
2
10
?
? m
Order of
diffraction
(n)
Distance between the
central bright spot and n
th

fringe (xn )
2
10
?
? m
Particle size
2
n
nD
d
x
?
?
m






23

Wavelength, ? =
?????? ?? 4
????
= ------------
Mean wavelength of the given laser light, ? = -------------- m
(ii) Grain size or diameter of the grain. 2d =
?????? ?? ??
Order of differaction, n = --------------
Wavelength of laser light used, ? = ------------- m
Distance between glass plate and the screen, D = ------------ m
Distance between central bright spot and the n
th
fringe,?? ?? = ------------ m
2d =
?????? ?? ??
=
= ------------ m








RESULT:
(i) Wavelength of the laser beam, ? = -------------- m
(ii) Average size of the particle = --------------- m

24


Optical fiber

To find numerical aperture, NA:

Sl. No.
Diameter of the circular patch
D(m)
Distance between the tip of the
fiber and the screen X (m)
NA =
?? (4?? 2
+?? 2
)
1
2





Mean NA =
Therefore, the acceptance angle, ? = Sin
-1
(NA) = -------------------
= -------------------


25

Expt. No.3(b) NUMERICAL APERTURE AND ACCEPTANCE ANGLE
AIM:
To measure the numerical aperture and the acceptance angle of the given fiber cable
APPARATUS REQUIRED:
Optical fiber cable with source, NA jig and in-line adaptor
FORMULA:
The numerical aperture, NA =
?? (4?? 2
+?? 2
)
1
2

Acceptance angle, ? = Sin
-1
(NA)
where,
D ? diameter of the circular patch (m)
X ? distance between the tip of the fiber and the screen (m)
PROCEDURE:
One end of the one metre fiber cable is connected to the laser light source and the other end
to the NA jig as shown in figure. The AC main is plugged in and the laser light is adjusted so that it appears at
the end of the fiber on the NA jig, the intensity knob is adjusted to get maximum intensity.
The white screen with the four concentric circles (10 mm, 20 mm, 30 mm and 40 mm diameter) is held
vertically at a suitable distance to make the red spot from the emitting fiber coincides with the 10 mm circle,
the diameter (D) of the spot is noted. The distance (X) of the screen from the fiber end is recorded.
The procedure is repeated for 20 mm, 30 mm, 40 mm diameter circles and the readings are tabulated.




26

















RESULT:
The numerical aperture, NA = ----------------
Acceptance angle, ? = ----------------




27




1. What is semiconductor diode laser?
2. What is meant by active material in laser?
3. What is meant by LASER?
4. What is stimulated emission?
5. What are the characteristics of laser radiation?
6. What is homo?junction laser?
7. What is hetero?junction laser?
8. What are the applications of semiconductor laser?
9. What are the conditions required for laser action?
10. Define ? Numerical aperture







Viva ? voce
28


Lee?s disc setup


29

Expt. No. 4 THERMAL CONDUCTIVITY OF A BAD CONDUCTOR
BY LEE?S DISC METHOD

AIM:
To determine the coefficient of thermal conductivity of a bad conductor
APPARATUS REQUIRED:
Lee?s disc apparatus, bad conductors, stop-clock, thermometers, screw gauge, vernier calipers and
steam boiler
FORMULA:
Thermal conductivity of a bad conductor,
? ?
? ? ? ?
1 1
2 1
2
2 2
2
? ?
? ?
?
?
?
?
?
?
?
?
?
? k Wm
h r r
h r d
dt
d
MS
K
? ? ?
?

M ? Mass of the metallic disc (Kg)
S ? Specific heat capacity of the metallic disc ( J Kg
-1
K
-1
)
? rate of cooling at steady temperature (
o
C/s)
d ? thickness of the bad conductor (m)
h ? thickness of the metallic disc (m)
r?radius of the metallic disc (m)
1
? ? steady temperature of the steam chamber (
o
C)
2
? ? steady temperature of the Metallic disc (
o
C)

PROCEDURE:
The thickness of the bad conductor say card board and thickness of the metallic disc are determined
using a screw gauge. The radius of the metallic disc is found using a vernier caliper. The mass of a metallic
disc is also found using a common balance. The readings are tabulated.

30

To find the radius of the metallic disc (r) using Vernier Calipers
Least count = 0.01cm Zero error = ? ???div
Zero correction = ? ???cm
= --------- ?10
-2
m
Sl.No.
MSR
(x10
-2
m)
VSC
(div.)
OR = MSR +(VSC x LC)
(x10
-2
m)
CR = OR ? ZC
(x10
-2
m)
1
2
3
4

Mean radius, r = --------------------------------- x10
-2
m
To find the thickness of the bad conductor (d) using Screw gauge
Least count = 0.01mm Zero error = ? ???div
Zero correction = ? ???mm
Sl.No.
PSR
(x10
-3
m)
HSC
(div.)
OR = PSR + (HSC x LC)
(x10
-3
m)
CR = OR ? ZC
(x10
-3
m)
1.
2.
3.
4.

Mean, d = -------------------------------- x10
-3
m
31

The whole Lee?s disc apparatus is suspended from a stand as shown in the figure. The given bad
conductor is placed in between the metallic disc and the steam chamber. Two thermometers T1 and T2 are
inserted into the respective holes.
Steam from the steam boiler is passed into the steam chamber until the temperature of the steam
chamber and the metallic disc are steady. The Steady temperature (?1) of the steam chamber and (?2) of the
metallic disc recorded by the thermometers are noted.
Now the bad conductor is removed and the steam chamber is placed in direct contact with the metallic
disc. The temperature of the disc rapidly rises. When the temperature of the disc rises about 10
o
Cabove
?2
o
C, the steam chamber is carefully removed after cutting of the steam supply.
When the temperature of the disc reaches 10
o
C above the steady temperature of the disc i.e. (?2+
10)
o
C , stop clock is started. Time for every one degree celsius fall of temperature is noted until the metallic
disc attains a temperature (?2 - 10)
o
C.
A graph is drawn taking time along the x-axis and temperature along the y-axis. The cooling curve is
obtained .To obtain the rate of the cooling (
????
????
)
?? 2
from this graph, a triangle is drawn by taking 1
o
C above
and 1
o
Cbelow the steady temperature ?2. Then the slope AB / BC gives the rate of cooling at(
????
????
)
?? 2
. From
these readings and using the given formula thermal conductivity of the given bad conductor is calculated.










32

To find the thickness of the metallic disc (h) using screw gauge
Least count = 0.01mm Zero error = ? ???div
Zero correction = ? ???mm
Sl.No.
PSR
(x10
-3
m)
HSC
(div.)
TR = PSR + (HSC x LC)
(x10
-3
m)
Corrected reading
CR = TR ? ZC
(x10
-3
m)
1
2
3
4
5

Mean, h = ------------------------------ x10
-3
m
To determine the rate of cooling of metallic disc:
Time
s
Temperature
o
C
Time
s
Temperature
o
C







FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
2


PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science and fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems and use this knowledge to acquire
higher education.
2. Core competence
To train the students in Engineering Physics so as to apply their knowledge and training to compare,
and to analyze various engineering industrial problems for finding solutions.
3. Breadth
To provide relevant training and experience to bridge the gap between theoretical learning and
practice that enables them to find solutions for the real time problems in industry and to design products.
4. Professionalism
To inculcate professional and effective communication skills, leadership qualities and team spirit for
the students to make them multi-faceted personalities and develop their ability to relate engineering issues
to broader social context.
5. Lifelong learning/ethics
To demonstrate and practice ethical and professional responsibilities in the industry and society by
and large, through commitment and lifelong learning needed for successful professional career.





3


PROGRAMME OUTCOMES (POs)

a) To demonstrate and apply knowledge of Mathematics, Science and Engineering fundamentals in
Engineering physics
b) To determine the Moment of Inertia of given disc and Rigidity modulus of the given wire using
Torsional Pendulum
c) To determine Young?s modulus of a given bar using Non-Uniform bending
d) To utilize laser source and grating to estimate the wave length, particle size of given powder and
Numerical Aperture & acceptance angle of given optical fiber
e) To find the Thermal conductivity of a bad conductor using Lee?s Disc method
f) To Measure the velocity of ultrasonic wave in a liquid and compressibility of the liquid usingultrasonic
Interferometer
g) To determine the wavelength of Hg source using grating and spectrometer
h) To find the thickness of a thin wire using Air- wedge method
i) To participate and succeed in competitive exams and visualize and work on laboratory and
multidisciplinary tasks











4


BS 8161 ? PHYSICSLABORATORY
(Common to all branches of B.E. / B.TechProgrammes)
SYLLABUS


To introduce different experiments to test basic understanding of physics concepts applied in optics, thermal
physics, properties of matter and liquids.

LIST OF EXPERIMENTS: PHYSICS LABORATORY(Any 5 Experiments)
1. Determination of Rigidity modulus ? Torsion pendulum
2. Determination of Young? s modulus by Non uniform bending method
3. (a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
4. Determination of thermal conductivity of a bad conductor ? Lee?s Disc method.
5. Determination of velocity of sound and compressibility of liquid ? Ultrasonic interferometer
6. Determination of wavelength of mercury spectrum ? spectrometer grating
7. Determination of band gap of a semiconductor
8. Determination of thickness of a thin wire ? Air wedge method




Completion of the course, the students will be able to: apply physics principles of optics and thermal physics
to evaluate engineering properties of materials.


COURSE OUTCOMES
COURSE OBJECTIVES
5

BS 8161 ? PHYSICS LABORATORY
CONTENTS

Sl.No. Name of the Experiment (any 5 experiments)
Page
No.
1.
Determination of Rigidity modulus ? Torsion pendulum
6
2.
Determination of Young ?s modulus by Non uniform bending method
12
3.
(a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
18
4.
Determination of thermal conductivity of a bad conductor ? Lee ?s Disc method.
28
5.
Determination of velocity of sound and compressibility of liquid ? Ultrasonic
interferometer
37
6.
Determination of wavelength of mercury spectrum ? spectrometer grating
42
7.
Determination of thickness of a thin wire ? Air wedge method
48
MEASURING INSTRUMENTS
M1 Screw gauge 54
M2 Vernier Calipers 58
M3 Travelling Microscope 62
M4 Spectrometer 66








6

TORSIONAL PENDULUM










7

Expt. No.1 TORSIONAL PENDULUM

AIM:
To determine the moment of inertia of the given disc and hence to determine the rigidity modulus of
the material of the given suspension wire by torsional oscillations
APPARATUS REQUIRED:
Torsional pendulum, two equal masses, stop clock, screw gauge and meter scale

FORMULA:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
where
m ?mass of the cylinder placed on the disc (kg)
To ?period of the pendulum for a length of l without mass (s)
T1?period of the pendulum for the same length when mass m is placed at a distance d 1
from the center of the suspension wire (s)
T2?period of the pendulum for the same length when mass m is placed at a distance d 2
from the center of the suspension wire (s)
a ? radius of the suspension wire (m)




8

1. To determine the time period of the disc:
Length of the wire (l)= --------
2
10
?
? m
Position of the equal
masses
Time for 10 oscillations Time period
(one oscillation)
s
Trial-1
s
Trial-2
s
Mean
s
Without any masses T0
With masses at
d1 = x10
-2
m
T1
With masses at
d2 = x10
-2
m
T2

2. To determine the radius of the wire:
Least count =0 .01 mm. Zero Error ZE = --------- divisions
Zero Correction ZC = ---------- mm

Sl.No.
Pitch Scale
Reading
PSR
3
10
?
? m
Head Scale
Coincidence
HSC
div
Observed reading
OR = PSR + (HSCXLC)
3
10
?
? m
Correct reading
CR = OR ? ZC
3
10
?
? m




Mean = ----------------
3
10
?
? m



9

PROCEDURE:
Torsional pendulum is suspended from vertical chuck. The length of the suspension wire is measured
between the vertical chuck and the chuck attached to the uniform circular disc (i). The circular disc is twisted
slightly without masses on the disc. Now it executes torsional oscillations. Care is taken to see that the disc
oscillates without wobbling. Time taken for 20 oscillations is noted with the help of a stop clock. Two trials are
taken. The average of these two trial readings is calculated from which the period of oscillations is found out
as T0.
Two identical cylindrical masses each of mass m are symmetrically placed on the disc on either side
of the wire at a distance d from the center of the disc. As before the disc is gently twisted. Time taken for 20
oscillations is noted from which the period of oscillation is calculated as T1.
The cylindrical masses are placed at a distance d2 from the center and the experiment is repeated.
The mean time period of oscillations is calculated T2.
The diameter of the specimen wire is measured accurately with the help of the screw gauge, at
various places on the wire. The average diameter and hence the radius of the wire is calculated as r.
Moment of inertia and the rigidity modulus are determined by the substituting the value of m, T 0, T1, T2,
T3, and l in the formula.










10

CALCULATION:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2

Mass of cylindrical mass, m = ----------- ? 10
-3
kg
Closest distance of the mass from the centre of the suspension wire, d1 = ------------ ? 10
-2
m
Farthest distance of the mass from the centre of suspension wire, d2= ------------? 10
-2
m
Period of oscillation without mass, To = ------------- s
Period of oscillation with mass at d1, T1= ------------ s
Period of oscillation with mass at d2, T2 = ------------- s

Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
= --------------- kg m
2
= --------------- kg m
2

Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
Moment of inertia, I = ------------------ kg m
2
Length of the wire, l = ------------------- ? 10
-2
m
Time of oscillation, To = ------------------ s
Radius of the wire, a = ------------------- ? 10
-3
m
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
= ----------------------
Rigidity modulus, n = ------------------- Nm
-2
11









RESULT:
(i)
The moment of inertia of the given circular disc, I = --------------- kg m
2
(ii)
The rigidity modulus of the material of the given wire, n = -------------- Nm
-2




1. State Hooke?s law.
2. Define ?Rigidity modulus
3. Define ?Moment of inertia
4. What is meant by torsional oscillation?
5. What is period of oscillation?
6. What is meant by twisting couple?
7. Define ? Shearing stress
8. Define ? Shearing strain
9. What is the unit of rigidity modulus?
10. What are the applications of torsional pendulum?


Viva ? voce
12


Young?s Modulus ? Non Uniform Bending
To determine depression (y):
L.C =.001cm M = ___________
3
10
?
? kg

Sl.No

Load


3
10
?
?
k
g
Microscope reading
Mean

2
10
?
? m
Depression
y for M kg

2
10
?
? m
Loading Unloading
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
1 W
2 W+50
3 W+100
4 W+150
5 W+200
6 W+250

Mean (y) = ----------
2
10
?
? m





13

Expt. No.2 YOUNG?S MODULUS BY NON ? UNIFORM BENDING
AIM:
To determine the young?s modulus of the material of the given bar, by non-uniform bending method
APPARATUS REQUIRED:
Travelling microscope, wooden bar, knife- edge, weights hanger, slotted weight, vernier calipers,
screw gauge and pin
FORMULA:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Where,
g ? acceleration due to gravity (9.8 ms
-2
)
l ? length of the bar between two knife edges (m)
b ? breadth of the bar (m)
d ? thickness of the bar (m)
y ? depressiont in the scale reading due to the change of mass M (m)
PROCEDURE:
The given wooden bar, for which young?s modulus is to be determined, is paced symmetrically on the
two knife edges. The distance between the knife edges is measured as the length of the bar (l). It is adjusted
to be, say, 60 cm. the weight hanger is suspended at the centre of the bar. A pin is held vertically at the
centre of the bar with the help of wax.
The given bar is brought to elastic mood by loading and unloading the bar with slotted weights in steps
of 50 g. This is repeated for two or three times. With the hanger as dead load W, the microscope is focused on
to the tip of the pin. The tangential screw of the microscope is adjusted so that the image of the tip of the pin
just touches the horizontal cross wire of the eyepiece. The main scale reading and the vernier scale
coincidence corresponding to this position are noted.
14

To find the breadth using vernier calipers, b:
Least count = ---------- cm Zero error = --------- div.
= ---------- ?10
-2
m Zero correction = ?ZE ?LC= --------- ?10
-2
m
Sl. No.

MSR
x 10
-2
m

VSC
div.
Observed reading
OR = MSR+(VSC ? LC)
x 10
-2
m
Correct Reading
CR = OR ? ZC
x 10
-2
m
1.

2.

3.


Mean, b = ------------------------?10
-2
m
To find the thickness using screw gauge, d:
Least count = ---------- mm Zero error = --------- div.
= ---------- ?10
-3
m Zero correction =ZE ?LC= --------- ?10
-3
m
Sl. No.

PSR
x 10
-3
m

HSC
div.
Observed reading
OR = PSR+ (HSC ? LC)
x 10
-3
m
Correct Reading
CR = OR ? ZC
x 10
-3
m
1.

2.

3.


Mean, d = ---------------------------?10
-3
m
15


The experiment is repeated by adding weights in steps of 50 g and every time the microscope is
adjusted for coincidence. The corresponding readings are noted. The experiment is repeated by unloading the
weights in steps of 50 g and the corresponding readings are tabulated. From this table, the shift in the scale
reading, say y, for a change of mass M is found out.
The breadth of the bar is measured at various points with the help of vernier calipers. Similarly the
thickness of the bar is measured by screw gauge. Substituting the values of M, y, l, d, b and g in the formula,
the young?s modulus of the material of the given bar is calculated.

















16

CALCULATION:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Acceleration due to gravity, g = 9.8 ms
-2
Length of the bar between two knife edges, l = ------------ ?10
-2
m
Breadth of the bar, b = ----------- ?10
-2
m
Thickness of the bar, d = ----------- ?10
-3
m
y = -----------?10
-2
m
E =
???? ?? 2
4?? ?? 3
?? Nm
-2

= ---------------
Young?s modulus, E = ----------- Nm
-2












17








RESULT:
Young?s modulus of the material of the given bar, E = ---------- Nm
-2


1. Define ? Young?s modulus
2. What is meant by Non-uniform bending?
3. Define ? Stress and strain
4. State Hooke?s law.
5. Define ? Neutral axis
6. What is the SI unit of young?s modulus?
7. Define ? Elastic limit
8. Define ? Elasticity
9. What are the factors affecting elasticity?
10. Define ? Elastic fatigue

Viva ? voce
18


To find the wavelength of the laser beam, ?:
Distance between the screen and the grating, D = ------------?10
-2
m
Number of lines per meter length of the grating, N = --------------- Lines per meter
Sl. No.
Order of diffraction,
(m)
Reading of the diffracted image
(?10
-2
m)
?? ?? = ?????? ?1
(
?? ?? ?? )
(deg.)
? =
?????? ?? ?? ????
m

Left side
(xi)
Right side
(xr)
Mean
(xm)










Mean, ? = ---------------- m


19

Expt. No.3(a) WAVELENGTH OF LASER LIGHT AND PARTICLE SIZE


AIM:
(i) To determine the wavelength of the given laser light.
(ii) To determine size of the given particle.
APPARATUS REQUIRED:
Diode laser, grating, screen, given micro particles, scale and screen.
FORMULAE:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
(ii) Grain size or diameter of the grain, 2d =
?????? ?? ?? m
Where
?? ?? ?angle of diffraction (deg.)
M ?order of diffraction (No unit)
N ?number of lines per metre length of the grating (m
-3
)
n ? order of diffraction (no unit)
? ? wavelength of laser light used (m)
D ? distance between the glass plate and the screen (m)
?? ?? - distance between the central bright spot and the nth fringe (m)
PROCEDURE:
TO FIND THE WAVELENGTH OF THE GIVEN LASER LIGHT:
The laser source, grating and screen are placed properly as shown in figure. The diode laser is kept
horizontally and switched on. Extreme care should be taken to avoid direct exposure of laser light on eyes.
20











21

The grating is held normal to the laser beam by adjusting the grating in such a way that the reflected
laser beam from the grating coincides with incident laser beam. Now the diffracted laser spots of various
orders can be seen on the screen, placed on the other side of the grating.

The distance of the different orders on either side of the central spot are measured as x randxi and are
tabulated.The mean value of xrandxiare calculated as xm for the m
th
order diffracted light. The distance
between the grating and the screen is measured as D. Hence, the angle of diffraction for the m
th
order,
?? ?? = ?????? ?1
(
?? ?? ?? )
The experiment is repeated for different orders and the readings are tabulated. From the table, ? for
each order is calculated. Substituting the value of ?, the corresponding order of diffraction and the number of
lines per meter length of the grating, the wavelength is calculated.

TO FIND THE SIZE OF THE GIVEN MICRO PARTICLE:

The lycopodium powder having fine micro particles of nearly same size is sprinkled on a glass plate.
This glass plate is kept between laser source and screen.
Now the particles present in the glass plate diffract laser beam from the source. By adjusting the
distance between the glass plate and the screen, a circular fringe pattern is obtained on the screen with
different orders of fingers. Now distance between the screen and the glass plate (D) is measured.
The distance of the first order and the second order fringe from the centre of spot are also measured.
Using the formula, the particle size is found out. The experiment is repeated for different D values.
22

To find the size of the particle:

CALCULATION:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
Number of lines per metre in the grating, N = ------------ lines per metre.
First order, m1; ?? 1
= ------------
Wavelength, ? =
?????? ?? 1
????
= ------------
Second order, m2; ?? 2
= ------------
Wavelength, ? =
?????? ?? 2
????
= ------------
Third order, m3; ?? 3
= ------------
Wavelength, ? =
?????? ?? 3
????
= ------------
Fourth order, m4; ?? 4
= ------------
Wavelength, ? =
?????? ?? 4
????
= -------------
Fifth order, m5; ?? 5
= ------------

Sl.No



Distance between
screen and glass
plate(D)
2
10
?
? m
Order of
diffraction
(n)
Distance between the
central bright spot and n
th

fringe (xn )
2
10
?
? m
Particle size
2
n
nD
d
x
?
?
m






23

Wavelength, ? =
?????? ?? 4
????
= ------------
Mean wavelength of the given laser light, ? = -------------- m
(ii) Grain size or diameter of the grain. 2d =
?????? ?? ??
Order of differaction, n = --------------
Wavelength of laser light used, ? = ------------- m
Distance between glass plate and the screen, D = ------------ m
Distance between central bright spot and the n
th
fringe,?? ?? = ------------ m
2d =
?????? ?? ??
=
= ------------ m








RESULT:
(i) Wavelength of the laser beam, ? = -------------- m
(ii) Average size of the particle = --------------- m

24


Optical fiber

To find numerical aperture, NA:

Sl. No.
Diameter of the circular patch
D(m)
Distance between the tip of the
fiber and the screen X (m)
NA =
?? (4?? 2
+?? 2
)
1
2





Mean NA =
Therefore, the acceptance angle, ? = Sin
-1
(NA) = -------------------
= -------------------


25

Expt. No.3(b) NUMERICAL APERTURE AND ACCEPTANCE ANGLE
AIM:
To measure the numerical aperture and the acceptance angle of the given fiber cable
APPARATUS REQUIRED:
Optical fiber cable with source, NA jig and in-line adaptor
FORMULA:
The numerical aperture, NA =
?? (4?? 2
+?? 2
)
1
2

Acceptance angle, ? = Sin
-1
(NA)
where,
D ? diameter of the circular patch (m)
X ? distance between the tip of the fiber and the screen (m)
PROCEDURE:
One end of the one metre fiber cable is connected to the laser light source and the other end
to the NA jig as shown in figure. The AC main is plugged in and the laser light is adjusted so that it appears at
the end of the fiber on the NA jig, the intensity knob is adjusted to get maximum intensity.
The white screen with the four concentric circles (10 mm, 20 mm, 30 mm and 40 mm diameter) is held
vertically at a suitable distance to make the red spot from the emitting fiber coincides with the 10 mm circle,
the diameter (D) of the spot is noted. The distance (X) of the screen from the fiber end is recorded.
The procedure is repeated for 20 mm, 30 mm, 40 mm diameter circles and the readings are tabulated.




26

















RESULT:
The numerical aperture, NA = ----------------
Acceptance angle, ? = ----------------




27




1. What is semiconductor diode laser?
2. What is meant by active material in laser?
3. What is meant by LASER?
4. What is stimulated emission?
5. What are the characteristics of laser radiation?
6. What is homo?junction laser?
7. What is hetero?junction laser?
8. What are the applications of semiconductor laser?
9. What are the conditions required for laser action?
10. Define ? Numerical aperture







Viva ? voce
28


Lee?s disc setup


29

Expt. No. 4 THERMAL CONDUCTIVITY OF A BAD CONDUCTOR
BY LEE?S DISC METHOD

AIM:
To determine the coefficient of thermal conductivity of a bad conductor
APPARATUS REQUIRED:
Lee?s disc apparatus, bad conductors, stop-clock, thermometers, screw gauge, vernier calipers and
steam boiler
FORMULA:
Thermal conductivity of a bad conductor,
? ?
? ? ? ?
1 1
2 1
2
2 2
2
? ?
? ?
?
?
?
?
?
?
?
?
?
? k Wm
h r r
h r d
dt
d
MS
K
? ? ?
?

M ? Mass of the metallic disc (Kg)
S ? Specific heat capacity of the metallic disc ( J Kg
-1
K
-1
)
? rate of cooling at steady temperature (
o
C/s)
d ? thickness of the bad conductor (m)
h ? thickness of the metallic disc (m)
r?radius of the metallic disc (m)
1
? ? steady temperature of the steam chamber (
o
C)
2
? ? steady temperature of the Metallic disc (
o
C)

PROCEDURE:
The thickness of the bad conductor say card board and thickness of the metallic disc are determined
using a screw gauge. The radius of the metallic disc is found using a vernier caliper. The mass of a metallic
disc is also found using a common balance. The readings are tabulated.

30

To find the radius of the metallic disc (r) using Vernier Calipers
Least count = 0.01cm Zero error = ? ???div
Zero correction = ? ???cm
= --------- ?10
-2
m
Sl.No.
MSR
(x10
-2
m)
VSC
(div.)
OR = MSR +(VSC x LC)
(x10
-2
m)
CR = OR ? ZC
(x10
-2
m)
1
2
3
4

Mean radius, r = --------------------------------- x10
-2
m
To find the thickness of the bad conductor (d) using Screw gauge
Least count = 0.01mm Zero error = ? ???div
Zero correction = ? ???mm
Sl.No.
PSR
(x10
-3
m)
HSC
(div.)
OR = PSR + (HSC x LC)
(x10
-3
m)
CR = OR ? ZC
(x10
-3
m)
1.
2.
3.
4.

Mean, d = -------------------------------- x10
-3
m
31

The whole Lee?s disc apparatus is suspended from a stand as shown in the figure. The given bad
conductor is placed in between the metallic disc and the steam chamber. Two thermometers T1 and T2 are
inserted into the respective holes.
Steam from the steam boiler is passed into the steam chamber until the temperature of the steam
chamber and the metallic disc are steady. The Steady temperature (?1) of the steam chamber and (?2) of the
metallic disc recorded by the thermometers are noted.
Now the bad conductor is removed and the steam chamber is placed in direct contact with the metallic
disc. The temperature of the disc rapidly rises. When the temperature of the disc rises about 10
o
Cabove
?2
o
C, the steam chamber is carefully removed after cutting of the steam supply.
When the temperature of the disc reaches 10
o
C above the steady temperature of the disc i.e. (?2+
10)
o
C , stop clock is started. Time for every one degree celsius fall of temperature is noted until the metallic
disc attains a temperature (?2 - 10)
o
C.
A graph is drawn taking time along the x-axis and temperature along the y-axis. The cooling curve is
obtained .To obtain the rate of the cooling (
????
????
)
?? 2
from this graph, a triangle is drawn by taking 1
o
C above
and 1
o
Cbelow the steady temperature ?2. Then the slope AB / BC gives the rate of cooling at(
????
????
)
?? 2
. From
these readings and using the given formula thermal conductivity of the given bad conductor is calculated.










32

To find the thickness of the metallic disc (h) using screw gauge
Least count = 0.01mm Zero error = ? ???div
Zero correction = ? ???mm
Sl.No.
PSR
(x10
-3
m)
HSC
(div.)
TR = PSR + (HSC x LC)
(x10
-3
m)
Corrected reading
CR = TR ? ZC
(x10
-3
m)
1
2
3
4
5

Mean, h = ------------------------------ x10
-3
m
To determine the rate of cooling of metallic disc:
Time
s
Temperature
o
C
Time
s
Temperature
o
C







33

CALCULATION:
Mass of the disc, m= ---------- x10
-3
kg
Specific heat capacity of the disc,c = 385 J kg
-1
K
-1
Rate of cooling at ?2,
????
????
= -------------- deg s
-1
Radius of the disc, r = ---------- x10
-2
m
Height of the disc, h = ---------- x10
-2
m
Thickness of the bad conductor, d = ---------- x10
-3 m
Temperature of steam, ?1 = ---------
o
C
Steady temperature of the disc, ?2 = -------------
o
C
Thermal conductivity,
? ?
? ? ? ?
1 1
2 1
2
2 2
2
? ?
? ?
?
?
?
?
?
?
?
?
?
? k Wm
h r r
h r d
dt
d
MS
K
? ? ?
?


= --------------------

= -------------------- Wm
-1
K
-1








FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
2


PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science and fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems and use this knowledge to acquire
higher education.
2. Core competence
To train the students in Engineering Physics so as to apply their knowledge and training to compare,
and to analyze various engineering industrial problems for finding solutions.
3. Breadth
To provide relevant training and experience to bridge the gap between theoretical learning and
practice that enables them to find solutions for the real time problems in industry and to design products.
4. Professionalism
To inculcate professional and effective communication skills, leadership qualities and team spirit for
the students to make them multi-faceted personalities and develop their ability to relate engineering issues
to broader social context.
5. Lifelong learning/ethics
To demonstrate and practice ethical and professional responsibilities in the industry and society by
and large, through commitment and lifelong learning needed for successful professional career.





3


PROGRAMME OUTCOMES (POs)

a) To demonstrate and apply knowledge of Mathematics, Science and Engineering fundamentals in
Engineering physics
b) To determine the Moment of Inertia of given disc and Rigidity modulus of the given wire using
Torsional Pendulum
c) To determine Young?s modulus of a given bar using Non-Uniform bending
d) To utilize laser source and grating to estimate the wave length, particle size of given powder and
Numerical Aperture & acceptance angle of given optical fiber
e) To find the Thermal conductivity of a bad conductor using Lee?s Disc method
f) To Measure the velocity of ultrasonic wave in a liquid and compressibility of the liquid usingultrasonic
Interferometer
g) To determine the wavelength of Hg source using grating and spectrometer
h) To find the thickness of a thin wire using Air- wedge method
i) To participate and succeed in competitive exams and visualize and work on laboratory and
multidisciplinary tasks











4


BS 8161 ? PHYSICSLABORATORY
(Common to all branches of B.E. / B.TechProgrammes)
SYLLABUS


To introduce different experiments to test basic understanding of physics concepts applied in optics, thermal
physics, properties of matter and liquids.

LIST OF EXPERIMENTS: PHYSICS LABORATORY(Any 5 Experiments)
1. Determination of Rigidity modulus ? Torsion pendulum
2. Determination of Young? s modulus by Non uniform bending method
3. (a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
4. Determination of thermal conductivity of a bad conductor ? Lee?s Disc method.
5. Determination of velocity of sound and compressibility of liquid ? Ultrasonic interferometer
6. Determination of wavelength of mercury spectrum ? spectrometer grating
7. Determination of band gap of a semiconductor
8. Determination of thickness of a thin wire ? Air wedge method




Completion of the course, the students will be able to: apply physics principles of optics and thermal physics
to evaluate engineering properties of materials.


COURSE OUTCOMES
COURSE OBJECTIVES
5

BS 8161 ? PHYSICS LABORATORY
CONTENTS

Sl.No. Name of the Experiment (any 5 experiments)
Page
No.
1.
Determination of Rigidity modulus ? Torsion pendulum
6
2.
Determination of Young ?s modulus by Non uniform bending method
12
3.
(a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
18
4.
Determination of thermal conductivity of a bad conductor ? Lee ?s Disc method.
28
5.
Determination of velocity of sound and compressibility of liquid ? Ultrasonic
interferometer
37
6.
Determination of wavelength of mercury spectrum ? spectrometer grating
42
7.
Determination of thickness of a thin wire ? Air wedge method
48
MEASURING INSTRUMENTS
M1 Screw gauge 54
M2 Vernier Calipers 58
M3 Travelling Microscope 62
M4 Spectrometer 66








6

TORSIONAL PENDULUM










7

Expt. No.1 TORSIONAL PENDULUM

AIM:
To determine the moment of inertia of the given disc and hence to determine the rigidity modulus of
the material of the given suspension wire by torsional oscillations
APPARATUS REQUIRED:
Torsional pendulum, two equal masses, stop clock, screw gauge and meter scale

FORMULA:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
where
m ?mass of the cylinder placed on the disc (kg)
To ?period of the pendulum for a length of l without mass (s)
T1?period of the pendulum for the same length when mass m is placed at a distance d 1
from the center of the suspension wire (s)
T2?period of the pendulum for the same length when mass m is placed at a distance d 2
from the center of the suspension wire (s)
a ? radius of the suspension wire (m)




8

1. To determine the time period of the disc:
Length of the wire (l)= --------
2
10
?
? m
Position of the equal
masses
Time for 10 oscillations Time period
(one oscillation)
s
Trial-1
s
Trial-2
s
Mean
s
Without any masses T0
With masses at
d1 = x10
-2
m
T1
With masses at
d2 = x10
-2
m
T2

2. To determine the radius of the wire:
Least count =0 .01 mm. Zero Error ZE = --------- divisions
Zero Correction ZC = ---------- mm

Sl.No.
Pitch Scale
Reading
PSR
3
10
?
? m
Head Scale
Coincidence
HSC
div
Observed reading
OR = PSR + (HSCXLC)
3
10
?
? m
Correct reading
CR = OR ? ZC
3
10
?
? m




Mean = ----------------
3
10
?
? m



9

PROCEDURE:
Torsional pendulum is suspended from vertical chuck. The length of the suspension wire is measured
between the vertical chuck and the chuck attached to the uniform circular disc (i). The circular disc is twisted
slightly without masses on the disc. Now it executes torsional oscillations. Care is taken to see that the disc
oscillates without wobbling. Time taken for 20 oscillations is noted with the help of a stop clock. Two trials are
taken. The average of these two trial readings is calculated from which the period of oscillations is found out
as T0.
Two identical cylindrical masses each of mass m are symmetrically placed on the disc on either side
of the wire at a distance d from the center of the disc. As before the disc is gently twisted. Time taken for 20
oscillations is noted from which the period of oscillation is calculated as T1.
The cylindrical masses are placed at a distance d2 from the center and the experiment is repeated.
The mean time period of oscillations is calculated T2.
The diameter of the specimen wire is measured accurately with the help of the screw gauge, at
various places on the wire. The average diameter and hence the radius of the wire is calculated as r.
Moment of inertia and the rigidity modulus are determined by the substituting the value of m, T 0, T1, T2,
T3, and l in the formula.










10

CALCULATION:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2

Mass of cylindrical mass, m = ----------- ? 10
-3
kg
Closest distance of the mass from the centre of the suspension wire, d1 = ------------ ? 10
-2
m
Farthest distance of the mass from the centre of suspension wire, d2= ------------? 10
-2
m
Period of oscillation without mass, To = ------------- s
Period of oscillation with mass at d1, T1= ------------ s
Period of oscillation with mass at d2, T2 = ------------- s

Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
= --------------- kg m
2
= --------------- kg m
2

Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
Moment of inertia, I = ------------------ kg m
2
Length of the wire, l = ------------------- ? 10
-2
m
Time of oscillation, To = ------------------ s
Radius of the wire, a = ------------------- ? 10
-3
m
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
= ----------------------
Rigidity modulus, n = ------------------- Nm
-2
11









RESULT:
(i)
The moment of inertia of the given circular disc, I = --------------- kg m
2
(ii)
The rigidity modulus of the material of the given wire, n = -------------- Nm
-2




1. State Hooke?s law.
2. Define ?Rigidity modulus
3. Define ?Moment of inertia
4. What is meant by torsional oscillation?
5. What is period of oscillation?
6. What is meant by twisting couple?
7. Define ? Shearing stress
8. Define ? Shearing strain
9. What is the unit of rigidity modulus?
10. What are the applications of torsional pendulum?


Viva ? voce
12


Young?s Modulus ? Non Uniform Bending
To determine depression (y):
L.C =.001cm M = ___________
3
10
?
? kg

Sl.No

Load


3
10
?
?
k
g
Microscope reading
Mean

2
10
?
? m
Depression
y for M kg

2
10
?
? m
Loading Unloading
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
1 W
2 W+50
3 W+100
4 W+150
5 W+200
6 W+250

Mean (y) = ----------
2
10
?
? m





13

Expt. No.2 YOUNG?S MODULUS BY NON ? UNIFORM BENDING
AIM:
To determine the young?s modulus of the material of the given bar, by non-uniform bending method
APPARATUS REQUIRED:
Travelling microscope, wooden bar, knife- edge, weights hanger, slotted weight, vernier calipers,
screw gauge and pin
FORMULA:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Where,
g ? acceleration due to gravity (9.8 ms
-2
)
l ? length of the bar between two knife edges (m)
b ? breadth of the bar (m)
d ? thickness of the bar (m)
y ? depressiont in the scale reading due to the change of mass M (m)
PROCEDURE:
The given wooden bar, for which young?s modulus is to be determined, is paced symmetrically on the
two knife edges. The distance between the knife edges is measured as the length of the bar (l). It is adjusted
to be, say, 60 cm. the weight hanger is suspended at the centre of the bar. A pin is held vertically at the
centre of the bar with the help of wax.
The given bar is brought to elastic mood by loading and unloading the bar with slotted weights in steps
of 50 g. This is repeated for two or three times. With the hanger as dead load W, the microscope is focused on
to the tip of the pin. The tangential screw of the microscope is adjusted so that the image of the tip of the pin
just touches the horizontal cross wire of the eyepiece. The main scale reading and the vernier scale
coincidence corresponding to this position are noted.
14

To find the breadth using vernier calipers, b:
Least count = ---------- cm Zero error = --------- div.
= ---------- ?10
-2
m Zero correction = ?ZE ?LC= --------- ?10
-2
m
Sl. No.

MSR
x 10
-2
m

VSC
div.
Observed reading
OR = MSR+(VSC ? LC)
x 10
-2
m
Correct Reading
CR = OR ? ZC
x 10
-2
m
1.

2.

3.


Mean, b = ------------------------?10
-2
m
To find the thickness using screw gauge, d:
Least count = ---------- mm Zero error = --------- div.
= ---------- ?10
-3
m Zero correction =ZE ?LC= --------- ?10
-3
m
Sl. No.

PSR
x 10
-3
m

HSC
div.
Observed reading
OR = PSR+ (HSC ? LC)
x 10
-3
m
Correct Reading
CR = OR ? ZC
x 10
-3
m
1.

2.

3.


Mean, d = ---------------------------?10
-3
m
15


The experiment is repeated by adding weights in steps of 50 g and every time the microscope is
adjusted for coincidence. The corresponding readings are noted. The experiment is repeated by unloading the
weights in steps of 50 g and the corresponding readings are tabulated. From this table, the shift in the scale
reading, say y, for a change of mass M is found out.
The breadth of the bar is measured at various points with the help of vernier calipers. Similarly the
thickness of the bar is measured by screw gauge. Substituting the values of M, y, l, d, b and g in the formula,
the young?s modulus of the material of the given bar is calculated.

















16

CALCULATION:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Acceleration due to gravity, g = 9.8 ms
-2
Length of the bar between two knife edges, l = ------------ ?10
-2
m
Breadth of the bar, b = ----------- ?10
-2
m
Thickness of the bar, d = ----------- ?10
-3
m
y = -----------?10
-2
m
E =
???? ?? 2
4?? ?? 3
?? Nm
-2

= ---------------
Young?s modulus, E = ----------- Nm
-2












17








RESULT:
Young?s modulus of the material of the given bar, E = ---------- Nm
-2


1. Define ? Young?s modulus
2. What is meant by Non-uniform bending?
3. Define ? Stress and strain
4. State Hooke?s law.
5. Define ? Neutral axis
6. What is the SI unit of young?s modulus?
7. Define ? Elastic limit
8. Define ? Elasticity
9. What are the factors affecting elasticity?
10. Define ? Elastic fatigue

Viva ? voce
18


To find the wavelength of the laser beam, ?:
Distance between the screen and the grating, D = ------------?10
-2
m
Number of lines per meter length of the grating, N = --------------- Lines per meter
Sl. No.
Order of diffraction,
(m)
Reading of the diffracted image
(?10
-2
m)
?? ?? = ?????? ?1
(
?? ?? ?? )
(deg.)
? =
?????? ?? ?? ????
m

Left side
(xi)
Right side
(xr)
Mean
(xm)










Mean, ? = ---------------- m


19

Expt. No.3(a) WAVELENGTH OF LASER LIGHT AND PARTICLE SIZE


AIM:
(i) To determine the wavelength of the given laser light.
(ii) To determine size of the given particle.
APPARATUS REQUIRED:
Diode laser, grating, screen, given micro particles, scale and screen.
FORMULAE:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
(ii) Grain size or diameter of the grain, 2d =
?????? ?? ?? m
Where
?? ?? ?angle of diffraction (deg.)
M ?order of diffraction (No unit)
N ?number of lines per metre length of the grating (m
-3
)
n ? order of diffraction (no unit)
? ? wavelength of laser light used (m)
D ? distance between the glass plate and the screen (m)
?? ?? - distance between the central bright spot and the nth fringe (m)
PROCEDURE:
TO FIND THE WAVELENGTH OF THE GIVEN LASER LIGHT:
The laser source, grating and screen are placed properly as shown in figure. The diode laser is kept
horizontally and switched on. Extreme care should be taken to avoid direct exposure of laser light on eyes.
20











21

The grating is held normal to the laser beam by adjusting the grating in such a way that the reflected
laser beam from the grating coincides with incident laser beam. Now the diffracted laser spots of various
orders can be seen on the screen, placed on the other side of the grating.

The distance of the different orders on either side of the central spot are measured as x randxi and are
tabulated.The mean value of xrandxiare calculated as xm for the m
th
order diffracted light. The distance
between the grating and the screen is measured as D. Hence, the angle of diffraction for the m
th
order,
?? ?? = ?????? ?1
(
?? ?? ?? )
The experiment is repeated for different orders and the readings are tabulated. From the table, ? for
each order is calculated. Substituting the value of ?, the corresponding order of diffraction and the number of
lines per meter length of the grating, the wavelength is calculated.

TO FIND THE SIZE OF THE GIVEN MICRO PARTICLE:

The lycopodium powder having fine micro particles of nearly same size is sprinkled on a glass plate.
This glass plate is kept between laser source and screen.
Now the particles present in the glass plate diffract laser beam from the source. By adjusting the
distance between the glass plate and the screen, a circular fringe pattern is obtained on the screen with
different orders of fingers. Now distance between the screen and the glass plate (D) is measured.
The distance of the first order and the second order fringe from the centre of spot are also measured.
Using the formula, the particle size is found out. The experiment is repeated for different D values.
22

To find the size of the particle:

CALCULATION:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
Number of lines per metre in the grating, N = ------------ lines per metre.
First order, m1; ?? 1
= ------------
Wavelength, ? =
?????? ?? 1
????
= ------------
Second order, m2; ?? 2
= ------------
Wavelength, ? =
?????? ?? 2
????
= ------------
Third order, m3; ?? 3
= ------------
Wavelength, ? =
?????? ?? 3
????
= ------------
Fourth order, m4; ?? 4
= ------------
Wavelength, ? =
?????? ?? 4
????
= -------------
Fifth order, m5; ?? 5
= ------------

Sl.No



Distance between
screen and glass
plate(D)
2
10
?
? m
Order of
diffraction
(n)
Distance between the
central bright spot and n
th

fringe (xn )
2
10
?
? m
Particle size
2
n
nD
d
x
?
?
m






23

Wavelength, ? =
?????? ?? 4
????
= ------------
Mean wavelength of the given laser light, ? = -------------- m
(ii) Grain size or diameter of the grain. 2d =
?????? ?? ??
Order of differaction, n = --------------
Wavelength of laser light used, ? = ------------- m
Distance between glass plate and the screen, D = ------------ m
Distance between central bright spot and the n
th
fringe,?? ?? = ------------ m
2d =
?????? ?? ??
=
= ------------ m








RESULT:
(i) Wavelength of the laser beam, ? = -------------- m
(ii) Average size of the particle = --------------- m

24


Optical fiber

To find numerical aperture, NA:

Sl. No.
Diameter of the circular patch
D(m)
Distance between the tip of the
fiber and the screen X (m)
NA =
?? (4?? 2
+?? 2
)
1
2





Mean NA =
Therefore, the acceptance angle, ? = Sin
-1
(NA) = -------------------
= -------------------


25

Expt. No.3(b) NUMERICAL APERTURE AND ACCEPTANCE ANGLE
AIM:
To measure the numerical aperture and the acceptance angle of the given fiber cable
APPARATUS REQUIRED:
Optical fiber cable with source, NA jig and in-line adaptor
FORMULA:
The numerical aperture, NA =
?? (4?? 2
+?? 2
)
1
2

Acceptance angle, ? = Sin
-1
(NA)
where,
D ? diameter of the circular patch (m)
X ? distance between the tip of the fiber and the screen (m)
PROCEDURE:
One end of the one metre fiber cable is connected to the laser light source and the other end
to the NA jig as shown in figure. The AC main is plugged in and the laser light is adjusted so that it appears at
the end of the fiber on the NA jig, the intensity knob is adjusted to get maximum intensity.
The white screen with the four concentric circles (10 mm, 20 mm, 30 mm and 40 mm diameter) is held
vertically at a suitable distance to make the red spot from the emitting fiber coincides with the 10 mm circle,
the diameter (D) of the spot is noted. The distance (X) of the screen from the fiber end is recorded.
The procedure is repeated for 20 mm, 30 mm, 40 mm diameter circles and the readings are tabulated.




26

















RESULT:
The numerical aperture, NA = ----------------
Acceptance angle, ? = ----------------




27




1. What is semiconductor diode laser?
2. What is meant by active material in laser?
3. What is meant by LASER?
4. What is stimulated emission?
5. What are the characteristics of laser radiation?
6. What is homo?junction laser?
7. What is hetero?junction laser?
8. What are the applications of semiconductor laser?
9. What are the conditions required for laser action?
10. Define ? Numerical aperture







Viva ? voce
28


Lee?s disc setup


29

Expt. No. 4 THERMAL CONDUCTIVITY OF A BAD CONDUCTOR
BY LEE?S DISC METHOD

AIM:
To determine the coefficient of thermal conductivity of a bad conductor
APPARATUS REQUIRED:
Lee?s disc apparatus, bad conductors, stop-clock, thermometers, screw gauge, vernier calipers and
steam boiler
FORMULA:
Thermal conductivity of a bad conductor,
? ?
? ? ? ?
1 1
2 1
2
2 2
2
? ?
? ?
?
?
?
?
?
?
?
?
?
? k Wm
h r r
h r d
dt
d
MS
K
? ? ?
?

M ? Mass of the metallic disc (Kg)
S ? Specific heat capacity of the metallic disc ( J Kg
-1
K
-1
)
? rate of cooling at steady temperature (
o
C/s)
d ? thickness of the bad conductor (m)
h ? thickness of the metallic disc (m)
r?radius of the metallic disc (m)
1
? ? steady temperature of the steam chamber (
o
C)
2
? ? steady temperature of the Metallic disc (
o
C)

PROCEDURE:
The thickness of the bad conductor say card board and thickness of the metallic disc are determined
using a screw gauge. The radius of the metallic disc is found using a vernier caliper. The mass of a metallic
disc is also found using a common balance. The readings are tabulated.

30

To find the radius of the metallic disc (r) using Vernier Calipers
Least count = 0.01cm Zero error = ? ???div
Zero correction = ? ???cm
= --------- ?10
-2
m
Sl.No.
MSR
(x10
-2
m)
VSC
(div.)
OR = MSR +(VSC x LC)
(x10
-2
m)
CR = OR ? ZC
(x10
-2
m)
1
2
3
4

Mean radius, r = --------------------------------- x10
-2
m
To find the thickness of the bad conductor (d) using Screw gauge
Least count = 0.01mm Zero error = ? ???div
Zero correction = ? ???mm
Sl.No.
PSR
(x10
-3
m)
HSC
(div.)
OR = PSR + (HSC x LC)
(x10
-3
m)
CR = OR ? ZC
(x10
-3
m)
1.
2.
3.
4.

Mean, d = -------------------------------- x10
-3
m
31

The whole Lee?s disc apparatus is suspended from a stand as shown in the figure. The given bad
conductor is placed in between the metallic disc and the steam chamber. Two thermometers T1 and T2 are
inserted into the respective holes.
Steam from the steam boiler is passed into the steam chamber until the temperature of the steam
chamber and the metallic disc are steady. The Steady temperature (?1) of the steam chamber and (?2) of the
metallic disc recorded by the thermometers are noted.
Now the bad conductor is removed and the steam chamber is placed in direct contact with the metallic
disc. The temperature of the disc rapidly rises. When the temperature of the disc rises about 10
o
Cabove
?2
o
C, the steam chamber is carefully removed after cutting of the steam supply.
When the temperature of the disc reaches 10
o
C above the steady temperature of the disc i.e. (?2+
10)
o
C , stop clock is started. Time for every one degree celsius fall of temperature is noted until the metallic
disc attains a temperature (?2 - 10)
o
C.
A graph is drawn taking time along the x-axis and temperature along the y-axis. The cooling curve is
obtained .To obtain the rate of the cooling (
????
????
)
?? 2
from this graph, a triangle is drawn by taking 1
o
C above
and 1
o
Cbelow the steady temperature ?2. Then the slope AB / BC gives the rate of cooling at(
????
????
)
?? 2
. From
these readings and using the given formula thermal conductivity of the given bad conductor is calculated.










32

To find the thickness of the metallic disc (h) using screw gauge
Least count = 0.01mm Zero error = ? ???div
Zero correction = ? ???mm
Sl.No.
PSR
(x10
-3
m)
HSC
(div.)
TR = PSR + (HSC x LC)
(x10
-3
m)
Corrected reading
CR = TR ? ZC
(x10
-3
m)
1
2
3
4
5

Mean, h = ------------------------------ x10
-3
m
To determine the rate of cooling of metallic disc:
Time
s
Temperature
o
C
Time
s
Temperature
o
C







33

CALCULATION:
Mass of the disc, m= ---------- x10
-3
kg
Specific heat capacity of the disc,c = 385 J kg
-1
K
-1
Rate of cooling at ?2,
????
????
= -------------- deg s
-1
Radius of the disc, r = ---------- x10
-2
m
Height of the disc, h = ---------- x10
-2
m
Thickness of the bad conductor, d = ---------- x10
-3 m
Temperature of steam, ?1 = ---------
o
C
Steady temperature of the disc, ?2 = -------------
o
C
Thermal conductivity,
? ?
? ? ? ?
1 1
2 1
2
2 2
2
? ?
? ?
?
?
?
?
?
?
?
?
?
? k Wm
h r r
h r d
dt
d
MS
K
? ? ?
?


= --------------------

= -------------------- Wm
-1
K
-1








34
















RESULT:
The thermal conductivity of the given bad conductor by Lee?s disc method, K = -------------- Wm
-1
K
-1







FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
2


PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science and fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems and use this knowledge to acquire
higher education.
2. Core competence
To train the students in Engineering Physics so as to apply their knowledge and training to compare,
and to analyze various engineering industrial problems for finding solutions.
3. Breadth
To provide relevant training and experience to bridge the gap between theoretical learning and
practice that enables them to find solutions for the real time problems in industry and to design products.
4. Professionalism
To inculcate professional and effective communication skills, leadership qualities and team spirit for
the students to make them multi-faceted personalities and develop their ability to relate engineering issues
to broader social context.
5. Lifelong learning/ethics
To demonstrate and practice ethical and professional responsibilities in the industry and society by
and large, through commitment and lifelong learning needed for successful professional career.





3


PROGRAMME OUTCOMES (POs)

a) To demonstrate and apply knowledge of Mathematics, Science and Engineering fundamentals in
Engineering physics
b) To determine the Moment of Inertia of given disc and Rigidity modulus of the given wire using
Torsional Pendulum
c) To determine Young?s modulus of a given bar using Non-Uniform bending
d) To utilize laser source and grating to estimate the wave length, particle size of given powder and
Numerical Aperture & acceptance angle of given optical fiber
e) To find the Thermal conductivity of a bad conductor using Lee?s Disc method
f) To Measure the velocity of ultrasonic wave in a liquid and compressibility of the liquid usingultrasonic
Interferometer
g) To determine the wavelength of Hg source using grating and spectrometer
h) To find the thickness of a thin wire using Air- wedge method
i) To participate and succeed in competitive exams and visualize and work on laboratory and
multidisciplinary tasks











4


BS 8161 ? PHYSICSLABORATORY
(Common to all branches of B.E. / B.TechProgrammes)
SYLLABUS


To introduce different experiments to test basic understanding of physics concepts applied in optics, thermal
physics, properties of matter and liquids.

LIST OF EXPERIMENTS: PHYSICS LABORATORY(Any 5 Experiments)
1. Determination of Rigidity modulus ? Torsion pendulum
2. Determination of Young? s modulus by Non uniform bending method
3. (a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
4. Determination of thermal conductivity of a bad conductor ? Lee?s Disc method.
5. Determination of velocity of sound and compressibility of liquid ? Ultrasonic interferometer
6. Determination of wavelength of mercury spectrum ? spectrometer grating
7. Determination of band gap of a semiconductor
8. Determination of thickness of a thin wire ? Air wedge method




Completion of the course, the students will be able to: apply physics principles of optics and thermal physics
to evaluate engineering properties of materials.


COURSE OUTCOMES
COURSE OBJECTIVES
5

BS 8161 ? PHYSICS LABORATORY
CONTENTS

Sl.No. Name of the Experiment (any 5 experiments)
Page
No.
1.
Determination of Rigidity modulus ? Torsion pendulum
6
2.
Determination of Young ?s modulus by Non uniform bending method
12
3.
(a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
18
4.
Determination of thermal conductivity of a bad conductor ? Lee ?s Disc method.
28
5.
Determination of velocity of sound and compressibility of liquid ? Ultrasonic
interferometer
37
6.
Determination of wavelength of mercury spectrum ? spectrometer grating
42
7.
Determination of thickness of a thin wire ? Air wedge method
48
MEASURING INSTRUMENTS
M1 Screw gauge 54
M2 Vernier Calipers 58
M3 Travelling Microscope 62
M4 Spectrometer 66








6

TORSIONAL PENDULUM










7

Expt. No.1 TORSIONAL PENDULUM

AIM:
To determine the moment of inertia of the given disc and hence to determine the rigidity modulus of
the material of the given suspension wire by torsional oscillations
APPARATUS REQUIRED:
Torsional pendulum, two equal masses, stop clock, screw gauge and meter scale

FORMULA:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
where
m ?mass of the cylinder placed on the disc (kg)
To ?period of the pendulum for a length of l without mass (s)
T1?period of the pendulum for the same length when mass m is placed at a distance d 1
from the center of the suspension wire (s)
T2?period of the pendulum for the same length when mass m is placed at a distance d 2
from the center of the suspension wire (s)
a ? radius of the suspension wire (m)




8

1. To determine the time period of the disc:
Length of the wire (l)= --------
2
10
?
? m
Position of the equal
masses
Time for 10 oscillations Time period
(one oscillation)
s
Trial-1
s
Trial-2
s
Mean
s
Without any masses T0
With masses at
d1 = x10
-2
m
T1
With masses at
d2 = x10
-2
m
T2

2. To determine the radius of the wire:
Least count =0 .01 mm. Zero Error ZE = --------- divisions
Zero Correction ZC = ---------- mm

Sl.No.
Pitch Scale
Reading
PSR
3
10
?
? m
Head Scale
Coincidence
HSC
div
Observed reading
OR = PSR + (HSCXLC)
3
10
?
? m
Correct reading
CR = OR ? ZC
3
10
?
? m




Mean = ----------------
3
10
?
? m



9

PROCEDURE:
Torsional pendulum is suspended from vertical chuck. The length of the suspension wire is measured
between the vertical chuck and the chuck attached to the uniform circular disc (i). The circular disc is twisted
slightly without masses on the disc. Now it executes torsional oscillations. Care is taken to see that the disc
oscillates without wobbling. Time taken for 20 oscillations is noted with the help of a stop clock. Two trials are
taken. The average of these two trial readings is calculated from which the period of oscillations is found out
as T0.
Two identical cylindrical masses each of mass m are symmetrically placed on the disc on either side
of the wire at a distance d from the center of the disc. As before the disc is gently twisted. Time taken for 20
oscillations is noted from which the period of oscillation is calculated as T1.
The cylindrical masses are placed at a distance d2 from the center and the experiment is repeated.
The mean time period of oscillations is calculated T2.
The diameter of the specimen wire is measured accurately with the help of the screw gauge, at
various places on the wire. The average diameter and hence the radius of the wire is calculated as r.
Moment of inertia and the rigidity modulus are determined by the substituting the value of m, T 0, T1, T2,
T3, and l in the formula.










10

CALCULATION:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2

Mass of cylindrical mass, m = ----------- ? 10
-3
kg
Closest distance of the mass from the centre of the suspension wire, d1 = ------------ ? 10
-2
m
Farthest distance of the mass from the centre of suspension wire, d2= ------------? 10
-2
m
Period of oscillation without mass, To = ------------- s
Period of oscillation with mass at d1, T1= ------------ s
Period of oscillation with mass at d2, T2 = ------------- s

Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
= --------------- kg m
2
= --------------- kg m
2

Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
Moment of inertia, I = ------------------ kg m
2
Length of the wire, l = ------------------- ? 10
-2
m
Time of oscillation, To = ------------------ s
Radius of the wire, a = ------------------- ? 10
-3
m
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
= ----------------------
Rigidity modulus, n = ------------------- Nm
-2
11









RESULT:
(i)
The moment of inertia of the given circular disc, I = --------------- kg m
2
(ii)
The rigidity modulus of the material of the given wire, n = -------------- Nm
-2




1. State Hooke?s law.
2. Define ?Rigidity modulus
3. Define ?Moment of inertia
4. What is meant by torsional oscillation?
5. What is period of oscillation?
6. What is meant by twisting couple?
7. Define ? Shearing stress
8. Define ? Shearing strain
9. What is the unit of rigidity modulus?
10. What are the applications of torsional pendulum?


Viva ? voce
12


Young?s Modulus ? Non Uniform Bending
To determine depression (y):
L.C =.001cm M = ___________
3
10
?
? kg

Sl.No

Load


3
10
?
?
k
g
Microscope reading
Mean

2
10
?
? m
Depression
y for M kg

2
10
?
? m
Loading Unloading
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
1 W
2 W+50
3 W+100
4 W+150
5 W+200
6 W+250

Mean (y) = ----------
2
10
?
? m





13

Expt. No.2 YOUNG?S MODULUS BY NON ? UNIFORM BENDING
AIM:
To determine the young?s modulus of the material of the given bar, by non-uniform bending method
APPARATUS REQUIRED:
Travelling microscope, wooden bar, knife- edge, weights hanger, slotted weight, vernier calipers,
screw gauge and pin
FORMULA:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Where,
g ? acceleration due to gravity (9.8 ms
-2
)
l ? length of the bar between two knife edges (m)
b ? breadth of the bar (m)
d ? thickness of the bar (m)
y ? depressiont in the scale reading due to the change of mass M (m)
PROCEDURE:
The given wooden bar, for which young?s modulus is to be determined, is paced symmetrically on the
two knife edges. The distance between the knife edges is measured as the length of the bar (l). It is adjusted
to be, say, 60 cm. the weight hanger is suspended at the centre of the bar. A pin is held vertically at the
centre of the bar with the help of wax.
The given bar is brought to elastic mood by loading and unloading the bar with slotted weights in steps
of 50 g. This is repeated for two or three times. With the hanger as dead load W, the microscope is focused on
to the tip of the pin. The tangential screw of the microscope is adjusted so that the image of the tip of the pin
just touches the horizontal cross wire of the eyepiece. The main scale reading and the vernier scale
coincidence corresponding to this position are noted.
14

To find the breadth using vernier calipers, b:
Least count = ---------- cm Zero error = --------- div.
= ---------- ?10
-2
m Zero correction = ?ZE ?LC= --------- ?10
-2
m
Sl. No.

MSR
x 10
-2
m

VSC
div.
Observed reading
OR = MSR+(VSC ? LC)
x 10
-2
m
Correct Reading
CR = OR ? ZC
x 10
-2
m
1.

2.

3.


Mean, b = ------------------------?10
-2
m
To find the thickness using screw gauge, d:
Least count = ---------- mm Zero error = --------- div.
= ---------- ?10
-3
m Zero correction =ZE ?LC= --------- ?10
-3
m
Sl. No.

PSR
x 10
-3
m

HSC
div.
Observed reading
OR = PSR+ (HSC ? LC)
x 10
-3
m
Correct Reading
CR = OR ? ZC
x 10
-3
m
1.

2.

3.


Mean, d = ---------------------------?10
-3
m
15


The experiment is repeated by adding weights in steps of 50 g and every time the microscope is
adjusted for coincidence. The corresponding readings are noted. The experiment is repeated by unloading the
weights in steps of 50 g and the corresponding readings are tabulated. From this table, the shift in the scale
reading, say y, for a change of mass M is found out.
The breadth of the bar is measured at various points with the help of vernier calipers. Similarly the
thickness of the bar is measured by screw gauge. Substituting the values of M, y, l, d, b and g in the formula,
the young?s modulus of the material of the given bar is calculated.

















16

CALCULATION:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Acceleration due to gravity, g = 9.8 ms
-2
Length of the bar between two knife edges, l = ------------ ?10
-2
m
Breadth of the bar, b = ----------- ?10
-2
m
Thickness of the bar, d = ----------- ?10
-3
m
y = -----------?10
-2
m
E =
???? ?? 2
4?? ?? 3
?? Nm
-2

= ---------------
Young?s modulus, E = ----------- Nm
-2












17








RESULT:
Young?s modulus of the material of the given bar, E = ---------- Nm
-2


1. Define ? Young?s modulus
2. What is meant by Non-uniform bending?
3. Define ? Stress and strain
4. State Hooke?s law.
5. Define ? Neutral axis
6. What is the SI unit of young?s modulus?
7. Define ? Elastic limit
8. Define ? Elasticity
9. What are the factors affecting elasticity?
10. Define ? Elastic fatigue

Viva ? voce
18


To find the wavelength of the laser beam, ?:
Distance between the screen and the grating, D = ------------?10
-2
m
Number of lines per meter length of the grating, N = --------------- Lines per meter
Sl. No.
Order of diffraction,
(m)
Reading of the diffracted image
(?10
-2
m)
?? ?? = ?????? ?1
(
?? ?? ?? )
(deg.)
? =
?????? ?? ?? ????
m

Left side
(xi)
Right side
(xr)
Mean
(xm)










Mean, ? = ---------------- m


19

Expt. No.3(a) WAVELENGTH OF LASER LIGHT AND PARTICLE SIZE


AIM:
(i) To determine the wavelength of the given laser light.
(ii) To determine size of the given particle.
APPARATUS REQUIRED:
Diode laser, grating, screen, given micro particles, scale and screen.
FORMULAE:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
(ii) Grain size or diameter of the grain, 2d =
?????? ?? ?? m
Where
?? ?? ?angle of diffraction (deg.)
M ?order of diffraction (No unit)
N ?number of lines per metre length of the grating (m
-3
)
n ? order of diffraction (no unit)
? ? wavelength of laser light used (m)
D ? distance between the glass plate and the screen (m)
?? ?? - distance between the central bright spot and the nth fringe (m)
PROCEDURE:
TO FIND THE WAVELENGTH OF THE GIVEN LASER LIGHT:
The laser source, grating and screen are placed properly as shown in figure. The diode laser is kept
horizontally and switched on. Extreme care should be taken to avoid direct exposure of laser light on eyes.
20











21

The grating is held normal to the laser beam by adjusting the grating in such a way that the reflected
laser beam from the grating coincides with incident laser beam. Now the diffracted laser spots of various
orders can be seen on the screen, placed on the other side of the grating.

The distance of the different orders on either side of the central spot are measured as x randxi and are
tabulated.The mean value of xrandxiare calculated as xm for the m
th
order diffracted light. The distance
between the grating and the screen is measured as D. Hence, the angle of diffraction for the m
th
order,
?? ?? = ?????? ?1
(
?? ?? ?? )
The experiment is repeated for different orders and the readings are tabulated. From the table, ? for
each order is calculated. Substituting the value of ?, the corresponding order of diffraction and the number of
lines per meter length of the grating, the wavelength is calculated.

TO FIND THE SIZE OF THE GIVEN MICRO PARTICLE:

The lycopodium powder having fine micro particles of nearly same size is sprinkled on a glass plate.
This glass plate is kept between laser source and screen.
Now the particles present in the glass plate diffract laser beam from the source. By adjusting the
distance between the glass plate and the screen, a circular fringe pattern is obtained on the screen with
different orders of fingers. Now distance between the screen and the glass plate (D) is measured.
The distance of the first order and the second order fringe from the centre of spot are also measured.
Using the formula, the particle size is found out. The experiment is repeated for different D values.
22

To find the size of the particle:

CALCULATION:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
Number of lines per metre in the grating, N = ------------ lines per metre.
First order, m1; ?? 1
= ------------
Wavelength, ? =
?????? ?? 1
????
= ------------
Second order, m2; ?? 2
= ------------
Wavelength, ? =
?????? ?? 2
????
= ------------
Third order, m3; ?? 3
= ------------
Wavelength, ? =
?????? ?? 3
????
= ------------
Fourth order, m4; ?? 4
= ------------
Wavelength, ? =
?????? ?? 4
????
= -------------
Fifth order, m5; ?? 5
= ------------

Sl.No



Distance between
screen and glass
plate(D)
2
10
?
? m
Order of
diffraction
(n)
Distance between the
central bright spot and n
th

fringe (xn )
2
10
?
? m
Particle size
2
n
nD
d
x
?
?
m






23

Wavelength, ? =
?????? ?? 4
????
= ------------
Mean wavelength of the given laser light, ? = -------------- m
(ii) Grain size or diameter of the grain. 2d =
?????? ?? ??
Order of differaction, n = --------------
Wavelength of laser light used, ? = ------------- m
Distance between glass plate and the screen, D = ------------ m
Distance between central bright spot and the n
th
fringe,?? ?? = ------------ m
2d =
?????? ?? ??
=
= ------------ m








RESULT:
(i) Wavelength of the laser beam, ? = -------------- m
(ii) Average size of the particle = --------------- m

24


Optical fiber

To find numerical aperture, NA:

Sl. No.
Diameter of the circular patch
D(m)
Distance between the tip of the
fiber and the screen X (m)
NA =
?? (4?? 2
+?? 2
)
1
2





Mean NA =
Therefore, the acceptance angle, ? = Sin
-1
(NA) = -------------------
= -------------------


25

Expt. No.3(b) NUMERICAL APERTURE AND ACCEPTANCE ANGLE
AIM:
To measure the numerical aperture and the acceptance angle of the given fiber cable
APPARATUS REQUIRED:
Optical fiber cable with source, NA jig and in-line adaptor
FORMULA:
The numerical aperture, NA =
?? (4?? 2
+?? 2
)
1
2

Acceptance angle, ? = Sin
-1
(NA)
where,
D ? diameter of the circular patch (m)
X ? distance between the tip of the fiber and the screen (m)
PROCEDURE:
One end of the one metre fiber cable is connected to the laser light source and the other end
to the NA jig as shown in figure. The AC main is plugged in and the laser light is adjusted so that it appears at
the end of the fiber on the NA jig, the intensity knob is adjusted to get maximum intensity.
The white screen with the four concentric circles (10 mm, 20 mm, 30 mm and 40 mm diameter) is held
vertically at a suitable distance to make the red spot from the emitting fiber coincides with the 10 mm circle,
the diameter (D) of the spot is noted. The distance (X) of the screen from the fiber end is recorded.
The procedure is repeated for 20 mm, 30 mm, 40 mm diameter circles and the readings are tabulated.




26

















RESULT:
The numerical aperture, NA = ----------------
Acceptance angle, ? = ----------------




27




1. What is semiconductor diode laser?
2. What is meant by active material in laser?
3. What is meant by LASER?
4. What is stimulated emission?
5. What are the characteristics of laser radiation?
6. What is homo?junction laser?
7. What is hetero?junction laser?
8. What are the applications of semiconductor laser?
9. What are the conditions required for laser action?
10. Define ? Numerical aperture







Viva ? voce
28


Lee?s disc setup


29

Expt. No. 4 THERMAL CONDUCTIVITY OF A BAD CONDUCTOR
BY LEE?S DISC METHOD

AIM:
To determine the coefficient of thermal conductivity of a bad conductor
APPARATUS REQUIRED:
Lee?s disc apparatus, bad conductors, stop-clock, thermometers, screw gauge, vernier calipers and
steam boiler
FORMULA:
Thermal conductivity of a bad conductor,
? ?
? ? ? ?
1 1
2 1
2
2 2
2
? ?
? ?
?
?
?
?
?
?
?
?
?
? k Wm
h r r
h r d
dt
d
MS
K
? ? ?
?

M ? Mass of the metallic disc (Kg)
S ? Specific heat capacity of the metallic disc ( J Kg
-1
K
-1
)
? rate of cooling at steady temperature (
o
C/s)
d ? thickness of the bad conductor (m)
h ? thickness of the metallic disc (m)
r?radius of the metallic disc (m)
1
? ? steady temperature of the steam chamber (
o
C)
2
? ? steady temperature of the Metallic disc (
o
C)

PROCEDURE:
The thickness of the bad conductor say card board and thickness of the metallic disc are determined
using a screw gauge. The radius of the metallic disc is found using a vernier caliper. The mass of a metallic
disc is also found using a common balance. The readings are tabulated.

30

To find the radius of the metallic disc (r) using Vernier Calipers
Least count = 0.01cm Zero error = ? ???div
Zero correction = ? ???cm
= --------- ?10
-2
m
Sl.No.
MSR
(x10
-2
m)
VSC
(div.)
OR = MSR +(VSC x LC)
(x10
-2
m)
CR = OR ? ZC
(x10
-2
m)
1
2
3
4

Mean radius, r = --------------------------------- x10
-2
m
To find the thickness of the bad conductor (d) using Screw gauge
Least count = 0.01mm Zero error = ? ???div
Zero correction = ? ???mm
Sl.No.
PSR
(x10
-3
m)
HSC
(div.)
OR = PSR + (HSC x LC)
(x10
-3
m)
CR = OR ? ZC
(x10
-3
m)
1.
2.
3.
4.

Mean, d = -------------------------------- x10
-3
m
31

The whole Lee?s disc apparatus is suspended from a stand as shown in the figure. The given bad
conductor is placed in between the metallic disc and the steam chamber. Two thermometers T1 and T2 are
inserted into the respective holes.
Steam from the steam boiler is passed into the steam chamber until the temperature of the steam
chamber and the metallic disc are steady. The Steady temperature (?1) of the steam chamber and (?2) of the
metallic disc recorded by the thermometers are noted.
Now the bad conductor is removed and the steam chamber is placed in direct contact with the metallic
disc. The temperature of the disc rapidly rises. When the temperature of the disc rises about 10
o
Cabove
?2
o
C, the steam chamber is carefully removed after cutting of the steam supply.
When the temperature of the disc reaches 10
o
C above the steady temperature of the disc i.e. (?2+
10)
o
C , stop clock is started. Time for every one degree celsius fall of temperature is noted until the metallic
disc attains a temperature (?2 - 10)
o
C.
A graph is drawn taking time along the x-axis and temperature along the y-axis. The cooling curve is
obtained .To obtain the rate of the cooling (
????
????
)
?? 2
from this graph, a triangle is drawn by taking 1
o
C above
and 1
o
Cbelow the steady temperature ?2. Then the slope AB / BC gives the rate of cooling at(
????
????
)
?? 2
. From
these readings and using the given formula thermal conductivity of the given bad conductor is calculated.










32

To find the thickness of the metallic disc (h) using screw gauge
Least count = 0.01mm Zero error = ? ???div
Zero correction = ? ???mm
Sl.No.
PSR
(x10
-3
m)
HSC
(div.)
TR = PSR + (HSC x LC)
(x10
-3
m)
Corrected reading
CR = TR ? ZC
(x10
-3
m)
1
2
3
4
5

Mean, h = ------------------------------ x10
-3
m
To determine the rate of cooling of metallic disc:
Time
s
Temperature
o
C
Time
s
Temperature
o
C







33

CALCULATION:
Mass of the disc, m= ---------- x10
-3
kg
Specific heat capacity of the disc,c = 385 J kg
-1
K
-1
Rate of cooling at ?2,
????
????
= -------------- deg s
-1
Radius of the disc, r = ---------- x10
-2
m
Height of the disc, h = ---------- x10
-2
m
Thickness of the bad conductor, d = ---------- x10
-3 m
Temperature of steam, ?1 = ---------
o
C
Steady temperature of the disc, ?2 = -------------
o
C
Thermal conductivity,
? ?
? ? ? ?
1 1
2 1
2
2 2
2
? ?
? ?
?
?
?
?
?
?
?
?
?
? k Wm
h r r
h r d
dt
d
MS
K
? ? ?
?


= --------------------

= -------------------- Wm
-1
K
-1








34
















RESULT:
The thermal conductivity of the given bad conductor by Lee?s disc method, K = -------------- Wm
-1
K
-1







35





1. What is meant by thermal conductivity?
2. What is meant by Rate of cooling?
3. Does the value of thermal conductivity depend on the dimension of the specimen?
4. Is there any reason to take the specimen in the form of a disc?
5. Can this method be used for good conductors?
6. What is lee's disc method?
7. What are the differences between good conductor and bad conductor?
8. What are the methods used to determine thermal conductivity of bad conductor?
9. What is meant by steady temperature?
10. What is meant by specific heat capacity?

Viva ? voce
FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
2


PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science and fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems and use this knowledge to acquire
higher education.
2. Core competence
To train the students in Engineering Physics so as to apply their knowledge and training to compare,
and to analyze various engineering industrial problems for finding solutions.
3. Breadth
To provide relevant training and experience to bridge the gap between theoretical learning and
practice that enables them to find solutions for the real time problems in industry and to design products.
4. Professionalism
To inculcate professional and effective communication skills, leadership qualities and team spirit for
the students to make them multi-faceted personalities and develop their ability to relate engineering issues
to broader social context.
5. Lifelong learning/ethics
To demonstrate and practice ethical and professional responsibilities in the industry and society by
and large, through commitment and lifelong learning needed for successful professional career.





3


PROGRAMME OUTCOMES (POs)

a) To demonstrate and apply knowledge of Mathematics, Science and Engineering fundamentals in
Engineering physics
b) To determine the Moment of Inertia of given disc and Rigidity modulus of the given wire using
Torsional Pendulum
c) To determine Young?s modulus of a given bar using Non-Uniform bending
d) To utilize laser source and grating to estimate the wave length, particle size of given powder and
Numerical Aperture & acceptance angle of given optical fiber
e) To find the Thermal conductivity of a bad conductor using Lee?s Disc method
f) To Measure the velocity of ultrasonic wave in a liquid and compressibility of the liquid usingultrasonic
Interferometer
g) To determine the wavelength of Hg source using grating and spectrometer
h) To find the thickness of a thin wire using Air- wedge method
i) To participate and succeed in competitive exams and visualize and work on laboratory and
multidisciplinary tasks











4


BS 8161 ? PHYSICSLABORATORY
(Common to all branches of B.E. / B.TechProgrammes)
SYLLABUS


To introduce different experiments to test basic understanding of physics concepts applied in optics, thermal
physics, properties of matter and liquids.

LIST OF EXPERIMENTS: PHYSICS LABORATORY(Any 5 Experiments)
1. Determination of Rigidity modulus ? Torsion pendulum
2. Determination of Young? s modulus by Non uniform bending method
3. (a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
4. Determination of thermal conductivity of a bad conductor ? Lee?s Disc method.
5. Determination of velocity of sound and compressibility of liquid ? Ultrasonic interferometer
6. Determination of wavelength of mercury spectrum ? spectrometer grating
7. Determination of band gap of a semiconductor
8. Determination of thickness of a thin wire ? Air wedge method




Completion of the course, the students will be able to: apply physics principles of optics and thermal physics
to evaluate engineering properties of materials.


COURSE OUTCOMES
COURSE OBJECTIVES
5

BS 8161 ? PHYSICS LABORATORY
CONTENTS

Sl.No. Name of the Experiment (any 5 experiments)
Page
No.
1.
Determination of Rigidity modulus ? Torsion pendulum
6
2.
Determination of Young ?s modulus by Non uniform bending method
12
3.
(a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
18
4.
Determination of thermal conductivity of a bad conductor ? Lee ?s Disc method.
28
5.
Determination of velocity of sound and compressibility of liquid ? Ultrasonic
interferometer
37
6.
Determination of wavelength of mercury spectrum ? spectrometer grating
42
7.
Determination of thickness of a thin wire ? Air wedge method
48
MEASURING INSTRUMENTS
M1 Screw gauge 54
M2 Vernier Calipers 58
M3 Travelling Microscope 62
M4 Spectrometer 66








6

TORSIONAL PENDULUM










7

Expt. No.1 TORSIONAL PENDULUM

AIM:
To determine the moment of inertia of the given disc and hence to determine the rigidity modulus of
the material of the given suspension wire by torsional oscillations
APPARATUS REQUIRED:
Torsional pendulum, two equal masses, stop clock, screw gauge and meter scale

FORMULA:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
where
m ?mass of the cylinder placed on the disc (kg)
To ?period of the pendulum for a length of l without mass (s)
T1?period of the pendulum for the same length when mass m is placed at a distance d 1
from the center of the suspension wire (s)
T2?period of the pendulum for the same length when mass m is placed at a distance d 2
from the center of the suspension wire (s)
a ? radius of the suspension wire (m)




8

1. To determine the time period of the disc:
Length of the wire (l)= --------
2
10
?
? m
Position of the equal
masses
Time for 10 oscillations Time period
(one oscillation)
s
Trial-1
s
Trial-2
s
Mean
s
Without any masses T0
With masses at
d1 = x10
-2
m
T1
With masses at
d2 = x10
-2
m
T2

2. To determine the radius of the wire:
Least count =0 .01 mm. Zero Error ZE = --------- divisions
Zero Correction ZC = ---------- mm

Sl.No.
Pitch Scale
Reading
PSR
3
10
?
? m
Head Scale
Coincidence
HSC
div
Observed reading
OR = PSR + (HSCXLC)
3
10
?
? m
Correct reading
CR = OR ? ZC
3
10
?
? m




Mean = ----------------
3
10
?
? m



9

PROCEDURE:
Torsional pendulum is suspended from vertical chuck. The length of the suspension wire is measured
between the vertical chuck and the chuck attached to the uniform circular disc (i). The circular disc is twisted
slightly without masses on the disc. Now it executes torsional oscillations. Care is taken to see that the disc
oscillates without wobbling. Time taken for 20 oscillations is noted with the help of a stop clock. Two trials are
taken. The average of these two trial readings is calculated from which the period of oscillations is found out
as T0.
Two identical cylindrical masses each of mass m are symmetrically placed on the disc on either side
of the wire at a distance d from the center of the disc. As before the disc is gently twisted. Time taken for 20
oscillations is noted from which the period of oscillation is calculated as T1.
The cylindrical masses are placed at a distance d2 from the center and the experiment is repeated.
The mean time period of oscillations is calculated T2.
The diameter of the specimen wire is measured accurately with the help of the screw gauge, at
various places on the wire. The average diameter and hence the radius of the wire is calculated as r.
Moment of inertia and the rigidity modulus are determined by the substituting the value of m, T 0, T1, T2,
T3, and l in the formula.










10

CALCULATION:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2

Mass of cylindrical mass, m = ----------- ? 10
-3
kg
Closest distance of the mass from the centre of the suspension wire, d1 = ------------ ? 10
-2
m
Farthest distance of the mass from the centre of suspension wire, d2= ------------? 10
-2
m
Period of oscillation without mass, To = ------------- s
Period of oscillation with mass at d1, T1= ------------ s
Period of oscillation with mass at d2, T2 = ------------- s

Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
= --------------- kg m
2
= --------------- kg m
2

Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
Moment of inertia, I = ------------------ kg m
2
Length of the wire, l = ------------------- ? 10
-2
m
Time of oscillation, To = ------------------ s
Radius of the wire, a = ------------------- ? 10
-3
m
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
= ----------------------
Rigidity modulus, n = ------------------- Nm
-2
11









RESULT:
(i)
The moment of inertia of the given circular disc, I = --------------- kg m
2
(ii)
The rigidity modulus of the material of the given wire, n = -------------- Nm
-2




1. State Hooke?s law.
2. Define ?Rigidity modulus
3. Define ?Moment of inertia
4. What is meant by torsional oscillation?
5. What is period of oscillation?
6. What is meant by twisting couple?
7. Define ? Shearing stress
8. Define ? Shearing strain
9. What is the unit of rigidity modulus?
10. What are the applications of torsional pendulum?


Viva ? voce
12


Young?s Modulus ? Non Uniform Bending
To determine depression (y):
L.C =.001cm M = ___________
3
10
?
? kg

Sl.No

Load


3
10
?
?
k
g
Microscope reading
Mean

2
10
?
? m
Depression
y for M kg

2
10
?
? m
Loading Unloading
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
1 W
2 W+50
3 W+100
4 W+150
5 W+200
6 W+250

Mean (y) = ----------
2
10
?
? m





13

Expt. No.2 YOUNG?S MODULUS BY NON ? UNIFORM BENDING
AIM:
To determine the young?s modulus of the material of the given bar, by non-uniform bending method
APPARATUS REQUIRED:
Travelling microscope, wooden bar, knife- edge, weights hanger, slotted weight, vernier calipers,
screw gauge and pin
FORMULA:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Where,
g ? acceleration due to gravity (9.8 ms
-2
)
l ? length of the bar between two knife edges (m)
b ? breadth of the bar (m)
d ? thickness of the bar (m)
y ? depressiont in the scale reading due to the change of mass M (m)
PROCEDURE:
The given wooden bar, for which young?s modulus is to be determined, is paced symmetrically on the
two knife edges. The distance between the knife edges is measured as the length of the bar (l). It is adjusted
to be, say, 60 cm. the weight hanger is suspended at the centre of the bar. A pin is held vertically at the
centre of the bar with the help of wax.
The given bar is brought to elastic mood by loading and unloading the bar with slotted weights in steps
of 50 g. This is repeated for two or three times. With the hanger as dead load W, the microscope is focused on
to the tip of the pin. The tangential screw of the microscope is adjusted so that the image of the tip of the pin
just touches the horizontal cross wire of the eyepiece. The main scale reading and the vernier scale
coincidence corresponding to this position are noted.
14

To find the breadth using vernier calipers, b:
Least count = ---------- cm Zero error = --------- div.
= ---------- ?10
-2
m Zero correction = ?ZE ?LC= --------- ?10
-2
m
Sl. No.

MSR
x 10
-2
m

VSC
div.
Observed reading
OR = MSR+(VSC ? LC)
x 10
-2
m
Correct Reading
CR = OR ? ZC
x 10
-2
m
1.

2.

3.


Mean, b = ------------------------?10
-2
m
To find the thickness using screw gauge, d:
Least count = ---------- mm Zero error = --------- div.
= ---------- ?10
-3
m Zero correction =ZE ?LC= --------- ?10
-3
m
Sl. No.

PSR
x 10
-3
m

HSC
div.
Observed reading
OR = PSR+ (HSC ? LC)
x 10
-3
m
Correct Reading
CR = OR ? ZC
x 10
-3
m
1.

2.

3.


Mean, d = ---------------------------?10
-3
m
15


The experiment is repeated by adding weights in steps of 50 g and every time the microscope is
adjusted for coincidence. The corresponding readings are noted. The experiment is repeated by unloading the
weights in steps of 50 g and the corresponding readings are tabulated. From this table, the shift in the scale
reading, say y, for a change of mass M is found out.
The breadth of the bar is measured at various points with the help of vernier calipers. Similarly the
thickness of the bar is measured by screw gauge. Substituting the values of M, y, l, d, b and g in the formula,
the young?s modulus of the material of the given bar is calculated.

















16

CALCULATION:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Acceleration due to gravity, g = 9.8 ms
-2
Length of the bar between two knife edges, l = ------------ ?10
-2
m
Breadth of the bar, b = ----------- ?10
-2
m
Thickness of the bar, d = ----------- ?10
-3
m
y = -----------?10
-2
m
E =
???? ?? 2
4?? ?? 3
?? Nm
-2

= ---------------
Young?s modulus, E = ----------- Nm
-2












17








RESULT:
Young?s modulus of the material of the given bar, E = ---------- Nm
-2


1. Define ? Young?s modulus
2. What is meant by Non-uniform bending?
3. Define ? Stress and strain
4. State Hooke?s law.
5. Define ? Neutral axis
6. What is the SI unit of young?s modulus?
7. Define ? Elastic limit
8. Define ? Elasticity
9. What are the factors affecting elasticity?
10. Define ? Elastic fatigue

Viva ? voce
18


To find the wavelength of the laser beam, ?:
Distance between the screen and the grating, D = ------------?10
-2
m
Number of lines per meter length of the grating, N = --------------- Lines per meter
Sl. No.
Order of diffraction,
(m)
Reading of the diffracted image
(?10
-2
m)
?? ?? = ?????? ?1
(
?? ?? ?? )
(deg.)
? =
?????? ?? ?? ????
m

Left side
(xi)
Right side
(xr)
Mean
(xm)










Mean, ? = ---------------- m


19

Expt. No.3(a) WAVELENGTH OF LASER LIGHT AND PARTICLE SIZE


AIM:
(i) To determine the wavelength of the given laser light.
(ii) To determine size of the given particle.
APPARATUS REQUIRED:
Diode laser, grating, screen, given micro particles, scale and screen.
FORMULAE:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
(ii) Grain size or diameter of the grain, 2d =
?????? ?? ?? m
Where
?? ?? ?angle of diffraction (deg.)
M ?order of diffraction (No unit)
N ?number of lines per metre length of the grating (m
-3
)
n ? order of diffraction (no unit)
? ? wavelength of laser light used (m)
D ? distance between the glass plate and the screen (m)
?? ?? - distance between the central bright spot and the nth fringe (m)
PROCEDURE:
TO FIND THE WAVELENGTH OF THE GIVEN LASER LIGHT:
The laser source, grating and screen are placed properly as shown in figure. The diode laser is kept
horizontally and switched on. Extreme care should be taken to avoid direct exposure of laser light on eyes.
20











21

The grating is held normal to the laser beam by adjusting the grating in such a way that the reflected
laser beam from the grating coincides with incident laser beam. Now the diffracted laser spots of various
orders can be seen on the screen, placed on the other side of the grating.

The distance of the different orders on either side of the central spot are measured as x randxi and are
tabulated.The mean value of xrandxiare calculated as xm for the m
th
order diffracted light. The distance
between the grating and the screen is measured as D. Hence, the angle of diffraction for the m
th
order,
?? ?? = ?????? ?1
(
?? ?? ?? )
The experiment is repeated for different orders and the readings are tabulated. From the table, ? for
each order is calculated. Substituting the value of ?, the corresponding order of diffraction and the number of
lines per meter length of the grating, the wavelength is calculated.

TO FIND THE SIZE OF THE GIVEN MICRO PARTICLE:

The lycopodium powder having fine micro particles of nearly same size is sprinkled on a glass plate.
This glass plate is kept between laser source and screen.
Now the particles present in the glass plate diffract laser beam from the source. By adjusting the
distance between the glass plate and the screen, a circular fringe pattern is obtained on the screen with
different orders of fingers. Now distance between the screen and the glass plate (D) is measured.
The distance of the first order and the second order fringe from the centre of spot are also measured.
Using the formula, the particle size is found out. The experiment is repeated for different D values.
22

To find the size of the particle:

CALCULATION:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
Number of lines per metre in the grating, N = ------------ lines per metre.
First order, m1; ?? 1
= ------------
Wavelength, ? =
?????? ?? 1
????
= ------------
Second order, m2; ?? 2
= ------------
Wavelength, ? =
?????? ?? 2
????
= ------------
Third order, m3; ?? 3
= ------------
Wavelength, ? =
?????? ?? 3
????
= ------------
Fourth order, m4; ?? 4
= ------------
Wavelength, ? =
?????? ?? 4
????
= -------------
Fifth order, m5; ?? 5
= ------------

Sl.No



Distance between
screen and glass
plate(D)
2
10
?
? m
Order of
diffraction
(n)
Distance between the
central bright spot and n
th

fringe (xn )
2
10
?
? m
Particle size
2
n
nD
d
x
?
?
m






23

Wavelength, ? =
?????? ?? 4
????
= ------------
Mean wavelength of the given laser light, ? = -------------- m
(ii) Grain size or diameter of the grain. 2d =
?????? ?? ??
Order of differaction, n = --------------
Wavelength of laser light used, ? = ------------- m
Distance between glass plate and the screen, D = ------------ m
Distance between central bright spot and the n
th
fringe,?? ?? = ------------ m
2d =
?????? ?? ??
=
= ------------ m








RESULT:
(i) Wavelength of the laser beam, ? = -------------- m
(ii) Average size of the particle = --------------- m

24


Optical fiber

To find numerical aperture, NA:

Sl. No.
Diameter of the circular patch
D(m)
Distance between the tip of the
fiber and the screen X (m)
NA =
?? (4?? 2
+?? 2
)
1
2





Mean NA =
Therefore, the acceptance angle, ? = Sin
-1
(NA) = -------------------
= -------------------


25

Expt. No.3(b) NUMERICAL APERTURE AND ACCEPTANCE ANGLE
AIM:
To measure the numerical aperture and the acceptance angle of the given fiber cable
APPARATUS REQUIRED:
Optical fiber cable with source, NA jig and in-line adaptor
FORMULA:
The numerical aperture, NA =
?? (4?? 2
+?? 2
)
1
2

Acceptance angle, ? = Sin
-1
(NA)
where,
D ? diameter of the circular patch (m)
X ? distance between the tip of the fiber and the screen (m)
PROCEDURE:
One end of the one metre fiber cable is connected to the laser light source and the other end
to the NA jig as shown in figure. The AC main is plugged in and the laser light is adjusted so that it appears at
the end of the fiber on the NA jig, the intensity knob is adjusted to get maximum intensity.
The white screen with the four concentric circles (10 mm, 20 mm, 30 mm and 40 mm diameter) is held
vertically at a suitable distance to make the red spot from the emitting fiber coincides with the 10 mm circle,
the diameter (D) of the spot is noted. The distance (X) of the screen from the fiber end is recorded.
The procedure is repeated for 20 mm, 30 mm, 40 mm diameter circles and the readings are tabulated.




26

















RESULT:
The numerical aperture, NA = ----------------
Acceptance angle, ? = ----------------




27




1. What is semiconductor diode laser?
2. What is meant by active material in laser?
3. What is meant by LASER?
4. What is stimulated emission?
5. What are the characteristics of laser radiation?
6. What is homo?junction laser?
7. What is hetero?junction laser?
8. What are the applications of semiconductor laser?
9. What are the conditions required for laser action?
10. Define ? Numerical aperture







Viva ? voce
28


Lee?s disc setup


29

Expt. No. 4 THERMAL CONDUCTIVITY OF A BAD CONDUCTOR
BY LEE?S DISC METHOD

AIM:
To determine the coefficient of thermal conductivity of a bad conductor
APPARATUS REQUIRED:
Lee?s disc apparatus, bad conductors, stop-clock, thermometers, screw gauge, vernier calipers and
steam boiler
FORMULA:
Thermal conductivity of a bad conductor,
? ?
? ? ? ?
1 1
2 1
2
2 2
2
? ?
? ?
?
?
?
?
?
?
?
?
?
? k Wm
h r r
h r d
dt
d
MS
K
? ? ?
?

M ? Mass of the metallic disc (Kg)
S ? Specific heat capacity of the metallic disc ( J Kg
-1
K
-1
)
? rate of cooling at steady temperature (
o
C/s)
d ? thickness of the bad conductor (m)
h ? thickness of the metallic disc (m)
r?radius of the metallic disc (m)
1
? ? steady temperature of the steam chamber (
o
C)
2
? ? steady temperature of the Metallic disc (
o
C)

PROCEDURE:
The thickness of the bad conductor say card board and thickness of the metallic disc are determined
using a screw gauge. The radius of the metallic disc is found using a vernier caliper. The mass of a metallic
disc is also found using a common balance. The readings are tabulated.

30

To find the radius of the metallic disc (r) using Vernier Calipers
Least count = 0.01cm Zero error = ? ???div
Zero correction = ? ???cm
= --------- ?10
-2
m
Sl.No.
MSR
(x10
-2
m)
VSC
(div.)
OR = MSR +(VSC x LC)
(x10
-2
m)
CR = OR ? ZC
(x10
-2
m)
1
2
3
4

Mean radius, r = --------------------------------- x10
-2
m
To find the thickness of the bad conductor (d) using Screw gauge
Least count = 0.01mm Zero error = ? ???div
Zero correction = ? ???mm
Sl.No.
PSR
(x10
-3
m)
HSC
(div.)
OR = PSR + (HSC x LC)
(x10
-3
m)
CR = OR ? ZC
(x10
-3
m)
1.
2.
3.
4.

Mean, d = -------------------------------- x10
-3
m
31

The whole Lee?s disc apparatus is suspended from a stand as shown in the figure. The given bad
conductor is placed in between the metallic disc and the steam chamber. Two thermometers T1 and T2 are
inserted into the respective holes.
Steam from the steam boiler is passed into the steam chamber until the temperature of the steam
chamber and the metallic disc are steady. The Steady temperature (?1) of the steam chamber and (?2) of the
metallic disc recorded by the thermometers are noted.
Now the bad conductor is removed and the steam chamber is placed in direct contact with the metallic
disc. The temperature of the disc rapidly rises. When the temperature of the disc rises about 10
o
Cabove
?2
o
C, the steam chamber is carefully removed after cutting of the steam supply.
When the temperature of the disc reaches 10
o
C above the steady temperature of the disc i.e. (?2+
10)
o
C , stop clock is started. Time for every one degree celsius fall of temperature is noted until the metallic
disc attains a temperature (?2 - 10)
o
C.
A graph is drawn taking time along the x-axis and temperature along the y-axis. The cooling curve is
obtained .To obtain the rate of the cooling (
????
????
)
?? 2
from this graph, a triangle is drawn by taking 1
o
C above
and 1
o
Cbelow the steady temperature ?2. Then the slope AB / BC gives the rate of cooling at(
????
????
)
?? 2
. From
these readings and using the given formula thermal conductivity of the given bad conductor is calculated.










32

To find the thickness of the metallic disc (h) using screw gauge
Least count = 0.01mm Zero error = ? ???div
Zero correction = ? ???mm
Sl.No.
PSR
(x10
-3
m)
HSC
(div.)
TR = PSR + (HSC x LC)
(x10
-3
m)
Corrected reading
CR = TR ? ZC
(x10
-3
m)
1
2
3
4
5

Mean, h = ------------------------------ x10
-3
m
To determine the rate of cooling of metallic disc:
Time
s
Temperature
o
C
Time
s
Temperature
o
C







33

CALCULATION:
Mass of the disc, m= ---------- x10
-3
kg
Specific heat capacity of the disc,c = 385 J kg
-1
K
-1
Rate of cooling at ?2,
????
????
= -------------- deg s
-1
Radius of the disc, r = ---------- x10
-2
m
Height of the disc, h = ---------- x10
-2
m
Thickness of the bad conductor, d = ---------- x10
-3 m
Temperature of steam, ?1 = ---------
o
C
Steady temperature of the disc, ?2 = -------------
o
C
Thermal conductivity,
? ?
? ? ? ?
1 1
2 1
2
2 2
2
? ?
? ?
?
?
?
?
?
?
?
?
?
? k Wm
h r r
h r d
dt
d
MS
K
? ? ?
?


= --------------------

= -------------------- Wm
-1
K
-1








34
















RESULT:
The thermal conductivity of the given bad conductor by Lee?s disc method, K = -------------- Wm
-1
K
-1







35





1. What is meant by thermal conductivity?
2. What is meant by Rate of cooling?
3. Does the value of thermal conductivity depend on the dimension of the specimen?
4. Is there any reason to take the specimen in the form of a disc?
5. Can this method be used for good conductors?
6. What is lee's disc method?
7. What are the differences between good conductor and bad conductor?
8. What are the methods used to determine thermal conductivity of bad conductor?
9. What is meant by steady temperature?
10. What is meant by specific heat capacity?

Viva ? voce
36




FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
2


PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science and fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems and use this knowledge to acquire
higher education.
2. Core competence
To train the students in Engineering Physics so as to apply their knowledge and training to compare,
and to analyze various engineering industrial problems for finding solutions.
3. Breadth
To provide relevant training and experience to bridge the gap between theoretical learning and
practice that enables them to find solutions for the real time problems in industry and to design products.
4. Professionalism
To inculcate professional and effective communication skills, leadership qualities and team spirit for
the students to make them multi-faceted personalities and develop their ability to relate engineering issues
to broader social context.
5. Lifelong learning/ethics
To demonstrate and practice ethical and professional responsibilities in the industry and society by
and large, through commitment and lifelong learning needed for successful professional career.





3


PROGRAMME OUTCOMES (POs)

a) To demonstrate and apply knowledge of Mathematics, Science and Engineering fundamentals in
Engineering physics
b) To determine the Moment of Inertia of given disc and Rigidity modulus of the given wire using
Torsional Pendulum
c) To determine Young?s modulus of a given bar using Non-Uniform bending
d) To utilize laser source and grating to estimate the wave length, particle size of given powder and
Numerical Aperture & acceptance angle of given optical fiber
e) To find the Thermal conductivity of a bad conductor using Lee?s Disc method
f) To Measure the velocity of ultrasonic wave in a liquid and compressibility of the liquid usingultrasonic
Interferometer
g) To determine the wavelength of Hg source using grating and spectrometer
h) To find the thickness of a thin wire using Air- wedge method
i) To participate and succeed in competitive exams and visualize and work on laboratory and
multidisciplinary tasks











4


BS 8161 ? PHYSICSLABORATORY
(Common to all branches of B.E. / B.TechProgrammes)
SYLLABUS


To introduce different experiments to test basic understanding of physics concepts applied in optics, thermal
physics, properties of matter and liquids.

LIST OF EXPERIMENTS: PHYSICS LABORATORY(Any 5 Experiments)
1. Determination of Rigidity modulus ? Torsion pendulum
2. Determination of Young? s modulus by Non uniform bending method
3. (a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
4. Determination of thermal conductivity of a bad conductor ? Lee?s Disc method.
5. Determination of velocity of sound and compressibility of liquid ? Ultrasonic interferometer
6. Determination of wavelength of mercury spectrum ? spectrometer grating
7. Determination of band gap of a semiconductor
8. Determination of thickness of a thin wire ? Air wedge method




Completion of the course, the students will be able to: apply physics principles of optics and thermal physics
to evaluate engineering properties of materials.


COURSE OUTCOMES
COURSE OBJECTIVES
5

BS 8161 ? PHYSICS LABORATORY
CONTENTS

Sl.No. Name of the Experiment (any 5 experiments)
Page
No.
1.
Determination of Rigidity modulus ? Torsion pendulum
6
2.
Determination of Young ?s modulus by Non uniform bending method
12
3.
(a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
18
4.
Determination of thermal conductivity of a bad conductor ? Lee ?s Disc method.
28
5.
Determination of velocity of sound and compressibility of liquid ? Ultrasonic
interferometer
37
6.
Determination of wavelength of mercury spectrum ? spectrometer grating
42
7.
Determination of thickness of a thin wire ? Air wedge method
48
MEASURING INSTRUMENTS
M1 Screw gauge 54
M2 Vernier Calipers 58
M3 Travelling Microscope 62
M4 Spectrometer 66








6

TORSIONAL PENDULUM










7

Expt. No.1 TORSIONAL PENDULUM

AIM:
To determine the moment of inertia of the given disc and hence to determine the rigidity modulus of
the material of the given suspension wire by torsional oscillations
APPARATUS REQUIRED:
Torsional pendulum, two equal masses, stop clock, screw gauge and meter scale

FORMULA:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
where
m ?mass of the cylinder placed on the disc (kg)
To ?period of the pendulum for a length of l without mass (s)
T1?period of the pendulum for the same length when mass m is placed at a distance d 1
from the center of the suspension wire (s)
T2?period of the pendulum for the same length when mass m is placed at a distance d 2
from the center of the suspension wire (s)
a ? radius of the suspension wire (m)




8

1. To determine the time period of the disc:
Length of the wire (l)= --------
2
10
?
? m
Position of the equal
masses
Time for 10 oscillations Time period
(one oscillation)
s
Trial-1
s
Trial-2
s
Mean
s
Without any masses T0
With masses at
d1 = x10
-2
m
T1
With masses at
d2 = x10
-2
m
T2

2. To determine the radius of the wire:
Least count =0 .01 mm. Zero Error ZE = --------- divisions
Zero Correction ZC = ---------- mm

Sl.No.
Pitch Scale
Reading
PSR
3
10
?
? m
Head Scale
Coincidence
HSC
div
Observed reading
OR = PSR + (HSCXLC)
3
10
?
? m
Correct reading
CR = OR ? ZC
3
10
?
? m




Mean = ----------------
3
10
?
? m



9

PROCEDURE:
Torsional pendulum is suspended from vertical chuck. The length of the suspension wire is measured
between the vertical chuck and the chuck attached to the uniform circular disc (i). The circular disc is twisted
slightly without masses on the disc. Now it executes torsional oscillations. Care is taken to see that the disc
oscillates without wobbling. Time taken for 20 oscillations is noted with the help of a stop clock. Two trials are
taken. The average of these two trial readings is calculated from which the period of oscillations is found out
as T0.
Two identical cylindrical masses each of mass m are symmetrically placed on the disc on either side
of the wire at a distance d from the center of the disc. As before the disc is gently twisted. Time taken for 20
oscillations is noted from which the period of oscillation is calculated as T1.
The cylindrical masses are placed at a distance d2 from the center and the experiment is repeated.
The mean time period of oscillations is calculated T2.
The diameter of the specimen wire is measured accurately with the help of the screw gauge, at
various places on the wire. The average diameter and hence the radius of the wire is calculated as r.
Moment of inertia and the rigidity modulus are determined by the substituting the value of m, T 0, T1, T2,
T3, and l in the formula.










10

CALCULATION:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2

Mass of cylindrical mass, m = ----------- ? 10
-3
kg
Closest distance of the mass from the centre of the suspension wire, d1 = ------------ ? 10
-2
m
Farthest distance of the mass from the centre of suspension wire, d2= ------------? 10
-2
m
Period of oscillation without mass, To = ------------- s
Period of oscillation with mass at d1, T1= ------------ s
Period of oscillation with mass at d2, T2 = ------------- s

Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
= --------------- kg m
2
= --------------- kg m
2

Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
Moment of inertia, I = ------------------ kg m
2
Length of the wire, l = ------------------- ? 10
-2
m
Time of oscillation, To = ------------------ s
Radius of the wire, a = ------------------- ? 10
-3
m
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
= ----------------------
Rigidity modulus, n = ------------------- Nm
-2
11









RESULT:
(i)
The moment of inertia of the given circular disc, I = --------------- kg m
2
(ii)
The rigidity modulus of the material of the given wire, n = -------------- Nm
-2




1. State Hooke?s law.
2. Define ?Rigidity modulus
3. Define ?Moment of inertia
4. What is meant by torsional oscillation?
5. What is period of oscillation?
6. What is meant by twisting couple?
7. Define ? Shearing stress
8. Define ? Shearing strain
9. What is the unit of rigidity modulus?
10. What are the applications of torsional pendulum?


Viva ? voce
12


Young?s Modulus ? Non Uniform Bending
To determine depression (y):
L.C =.001cm M = ___________
3
10
?
? kg

Sl.No

Load


3
10
?
?
k
g
Microscope reading
Mean

2
10
?
? m
Depression
y for M kg

2
10
?
? m
Loading Unloading
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
1 W
2 W+50
3 W+100
4 W+150
5 W+200
6 W+250

Mean (y) = ----------
2
10
?
? m





13

Expt. No.2 YOUNG?S MODULUS BY NON ? UNIFORM BENDING
AIM:
To determine the young?s modulus of the material of the given bar, by non-uniform bending method
APPARATUS REQUIRED:
Travelling microscope, wooden bar, knife- edge, weights hanger, slotted weight, vernier calipers,
screw gauge and pin
FORMULA:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Where,
g ? acceleration due to gravity (9.8 ms
-2
)
l ? length of the bar between two knife edges (m)
b ? breadth of the bar (m)
d ? thickness of the bar (m)
y ? depressiont in the scale reading due to the change of mass M (m)
PROCEDURE:
The given wooden bar, for which young?s modulus is to be determined, is paced symmetrically on the
two knife edges. The distance between the knife edges is measured as the length of the bar (l). It is adjusted
to be, say, 60 cm. the weight hanger is suspended at the centre of the bar. A pin is held vertically at the
centre of the bar with the help of wax.
The given bar is brought to elastic mood by loading and unloading the bar with slotted weights in steps
of 50 g. This is repeated for two or three times. With the hanger as dead load W, the microscope is focused on
to the tip of the pin. The tangential screw of the microscope is adjusted so that the image of the tip of the pin
just touches the horizontal cross wire of the eyepiece. The main scale reading and the vernier scale
coincidence corresponding to this position are noted.
14

To find the breadth using vernier calipers, b:
Least count = ---------- cm Zero error = --------- div.
= ---------- ?10
-2
m Zero correction = ?ZE ?LC= --------- ?10
-2
m
Sl. No.

MSR
x 10
-2
m

VSC
div.
Observed reading
OR = MSR+(VSC ? LC)
x 10
-2
m
Correct Reading
CR = OR ? ZC
x 10
-2
m
1.

2.

3.


Mean, b = ------------------------?10
-2
m
To find the thickness using screw gauge, d:
Least count = ---------- mm Zero error = --------- div.
= ---------- ?10
-3
m Zero correction =ZE ?LC= --------- ?10
-3
m
Sl. No.

PSR
x 10
-3
m

HSC
div.
Observed reading
OR = PSR+ (HSC ? LC)
x 10
-3
m
Correct Reading
CR = OR ? ZC
x 10
-3
m
1.

2.

3.


Mean, d = ---------------------------?10
-3
m
15


The experiment is repeated by adding weights in steps of 50 g and every time the microscope is
adjusted for coincidence. The corresponding readings are noted. The experiment is repeated by unloading the
weights in steps of 50 g and the corresponding readings are tabulated. From this table, the shift in the scale
reading, say y, for a change of mass M is found out.
The breadth of the bar is measured at various points with the help of vernier calipers. Similarly the
thickness of the bar is measured by screw gauge. Substituting the values of M, y, l, d, b and g in the formula,
the young?s modulus of the material of the given bar is calculated.

















16

CALCULATION:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Acceleration due to gravity, g = 9.8 ms
-2
Length of the bar between two knife edges, l = ------------ ?10
-2
m
Breadth of the bar, b = ----------- ?10
-2
m
Thickness of the bar, d = ----------- ?10
-3
m
y = -----------?10
-2
m
E =
???? ?? 2
4?? ?? 3
?? Nm
-2

= ---------------
Young?s modulus, E = ----------- Nm
-2












17








RESULT:
Young?s modulus of the material of the given bar, E = ---------- Nm
-2


1. Define ? Young?s modulus
2. What is meant by Non-uniform bending?
3. Define ? Stress and strain
4. State Hooke?s law.
5. Define ? Neutral axis
6. What is the SI unit of young?s modulus?
7. Define ? Elastic limit
8. Define ? Elasticity
9. What are the factors affecting elasticity?
10. Define ? Elastic fatigue

Viva ? voce
18


To find the wavelength of the laser beam, ?:
Distance between the screen and the grating, D = ------------?10
-2
m
Number of lines per meter length of the grating, N = --------------- Lines per meter
Sl. No.
Order of diffraction,
(m)
Reading of the diffracted image
(?10
-2
m)
?? ?? = ?????? ?1
(
?? ?? ?? )
(deg.)
? =
?????? ?? ?? ????
m

Left side
(xi)
Right side
(xr)
Mean
(xm)










Mean, ? = ---------------- m


19

Expt. No.3(a) WAVELENGTH OF LASER LIGHT AND PARTICLE SIZE


AIM:
(i) To determine the wavelength of the given laser light.
(ii) To determine size of the given particle.
APPARATUS REQUIRED:
Diode laser, grating, screen, given micro particles, scale and screen.
FORMULAE:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
(ii) Grain size or diameter of the grain, 2d =
?????? ?? ?? m
Where
?? ?? ?angle of diffraction (deg.)
M ?order of diffraction (No unit)
N ?number of lines per metre length of the grating (m
-3
)
n ? order of diffraction (no unit)
? ? wavelength of laser light used (m)
D ? distance between the glass plate and the screen (m)
?? ?? - distance between the central bright spot and the nth fringe (m)
PROCEDURE:
TO FIND THE WAVELENGTH OF THE GIVEN LASER LIGHT:
The laser source, grating and screen are placed properly as shown in figure. The diode laser is kept
horizontally and switched on. Extreme care should be taken to avoid direct exposure of laser light on eyes.
20











21

The grating is held normal to the laser beam by adjusting the grating in such a way that the reflected
laser beam from the grating coincides with incident laser beam. Now the diffracted laser spots of various
orders can be seen on the screen, placed on the other side of the grating.

The distance of the different orders on either side of the central spot are measured as x randxi and are
tabulated.The mean value of xrandxiare calculated as xm for the m
th
order diffracted light. The distance
between the grating and the screen is measured as D. Hence, the angle of diffraction for the m
th
order,
?? ?? = ?????? ?1
(
?? ?? ?? )
The experiment is repeated for different orders and the readings are tabulated. From the table, ? for
each order is calculated. Substituting the value of ?, the corresponding order of diffraction and the number of
lines per meter length of the grating, the wavelength is calculated.

TO FIND THE SIZE OF THE GIVEN MICRO PARTICLE:

The lycopodium powder having fine micro particles of nearly same size is sprinkled on a glass plate.
This glass plate is kept between laser source and screen.
Now the particles present in the glass plate diffract laser beam from the source. By adjusting the
distance between the glass plate and the screen, a circular fringe pattern is obtained on the screen with
different orders of fingers. Now distance between the screen and the glass plate (D) is measured.
The distance of the first order and the second order fringe from the centre of spot are also measured.
Using the formula, the particle size is found out. The experiment is repeated for different D values.
22

To find the size of the particle:

CALCULATION:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
Number of lines per metre in the grating, N = ------------ lines per metre.
First order, m1; ?? 1
= ------------
Wavelength, ? =
?????? ?? 1
????
= ------------
Second order, m2; ?? 2
= ------------
Wavelength, ? =
?????? ?? 2
????
= ------------
Third order, m3; ?? 3
= ------------
Wavelength, ? =
?????? ?? 3
????
= ------------
Fourth order, m4; ?? 4
= ------------
Wavelength, ? =
?????? ?? 4
????
= -------------
Fifth order, m5; ?? 5
= ------------

Sl.No



Distance between
screen and glass
plate(D)
2
10
?
? m
Order of
diffraction
(n)
Distance between the
central bright spot and n
th

fringe (xn )
2
10
?
? m
Particle size
2
n
nD
d
x
?
?
m






23

Wavelength, ? =
?????? ?? 4
????
= ------------
Mean wavelength of the given laser light, ? = -------------- m
(ii) Grain size or diameter of the grain. 2d =
?????? ?? ??
Order of differaction, n = --------------
Wavelength of laser light used, ? = ------------- m
Distance between glass plate and the screen, D = ------------ m
Distance between central bright spot and the n
th
fringe,?? ?? = ------------ m
2d =
?????? ?? ??
=
= ------------ m








RESULT:
(i) Wavelength of the laser beam, ? = -------------- m
(ii) Average size of the particle = --------------- m

24


Optical fiber

To find numerical aperture, NA:

Sl. No.
Diameter of the circular patch
D(m)
Distance between the tip of the
fiber and the screen X (m)
NA =
?? (4?? 2
+?? 2
)
1
2





Mean NA =
Therefore, the acceptance angle, ? = Sin
-1
(NA) = -------------------
= -------------------


25

Expt. No.3(b) NUMERICAL APERTURE AND ACCEPTANCE ANGLE
AIM:
To measure the numerical aperture and the acceptance angle of the given fiber cable
APPARATUS REQUIRED:
Optical fiber cable with source, NA jig and in-line adaptor
FORMULA:
The numerical aperture, NA =
?? (4?? 2
+?? 2
)
1
2

Acceptance angle, ? = Sin
-1
(NA)
where,
D ? diameter of the circular patch (m)
X ? distance between the tip of the fiber and the screen (m)
PROCEDURE:
One end of the one metre fiber cable is connected to the laser light source and the other end
to the NA jig as shown in figure. The AC main is plugged in and the laser light is adjusted so that it appears at
the end of the fiber on the NA jig, the intensity knob is adjusted to get maximum intensity.
The white screen with the four concentric circles (10 mm, 20 mm, 30 mm and 40 mm diameter) is held
vertically at a suitable distance to make the red spot from the emitting fiber coincides with the 10 mm circle,
the diameter (D) of the spot is noted. The distance (X) of the screen from the fiber end is recorded.
The procedure is repeated for 20 mm, 30 mm, 40 mm diameter circles and the readings are tabulated.




26

















RESULT:
The numerical aperture, NA = ----------------
Acceptance angle, ? = ----------------




27




1. What is semiconductor diode laser?
2. What is meant by active material in laser?
3. What is meant by LASER?
4. What is stimulated emission?
5. What are the characteristics of laser radiation?
6. What is homo?junction laser?
7. What is hetero?junction laser?
8. What are the applications of semiconductor laser?
9. What are the conditions required for laser action?
10. Define ? Numerical aperture







Viva ? voce
28


Lee?s disc setup


29

Expt. No. 4 THERMAL CONDUCTIVITY OF A BAD CONDUCTOR
BY LEE?S DISC METHOD

AIM:
To determine the coefficient of thermal conductivity of a bad conductor
APPARATUS REQUIRED:
Lee?s disc apparatus, bad conductors, stop-clock, thermometers, screw gauge, vernier calipers and
steam boiler
FORMULA:
Thermal conductivity of a bad conductor,
? ?
? ? ? ?
1 1
2 1
2
2 2
2
? ?
? ?
?
?
?
?
?
?
?
?
?
? k Wm
h r r
h r d
dt
d
MS
K
? ? ?
?

M ? Mass of the metallic disc (Kg)
S ? Specific heat capacity of the metallic disc ( J Kg
-1
K
-1
)
? rate of cooling at steady temperature (
o
C/s)
d ? thickness of the bad conductor (m)
h ? thickness of the metallic disc (m)
r?radius of the metallic disc (m)
1
? ? steady temperature of the steam chamber (
o
C)
2
? ? steady temperature of the Metallic disc (
o
C)

PROCEDURE:
The thickness of the bad conductor say card board and thickness of the metallic disc are determined
using a screw gauge. The radius of the metallic disc is found using a vernier caliper. The mass of a metallic
disc is also found using a common balance. The readings are tabulated.

30

To find the radius of the metallic disc (r) using Vernier Calipers
Least count = 0.01cm Zero error = ? ???div
Zero correction = ? ???cm
= --------- ?10
-2
m
Sl.No.
MSR
(x10
-2
m)
VSC
(div.)
OR = MSR +(VSC x LC)
(x10
-2
m)
CR = OR ? ZC
(x10
-2
m)
1
2
3
4

Mean radius, r = --------------------------------- x10
-2
m
To find the thickness of the bad conductor (d) using Screw gauge
Least count = 0.01mm Zero error = ? ???div
Zero correction = ? ???mm
Sl.No.
PSR
(x10
-3
m)
HSC
(div.)
OR = PSR + (HSC x LC)
(x10
-3
m)
CR = OR ? ZC
(x10
-3
m)
1.
2.
3.
4.

Mean, d = -------------------------------- x10
-3
m
31

The whole Lee?s disc apparatus is suspended from a stand as shown in the figure. The given bad
conductor is placed in between the metallic disc and the steam chamber. Two thermometers T1 and T2 are
inserted into the respective holes.
Steam from the steam boiler is passed into the steam chamber until the temperature of the steam
chamber and the metallic disc are steady. The Steady temperature (?1) of the steam chamber and (?2) of the
metallic disc recorded by the thermometers are noted.
Now the bad conductor is removed and the steam chamber is placed in direct contact with the metallic
disc. The temperature of the disc rapidly rises. When the temperature of the disc rises about 10
o
Cabove
?2
o
C, the steam chamber is carefully removed after cutting of the steam supply.
When the temperature of the disc reaches 10
o
C above the steady temperature of the disc i.e. (?2+
10)
o
C , stop clock is started. Time for every one degree celsius fall of temperature is noted until the metallic
disc attains a temperature (?2 - 10)
o
C.
A graph is drawn taking time along the x-axis and temperature along the y-axis. The cooling curve is
obtained .To obtain the rate of the cooling (
????
????
)
?? 2
from this graph, a triangle is drawn by taking 1
o
C above
and 1
o
Cbelow the steady temperature ?2. Then the slope AB / BC gives the rate of cooling at(
????
????
)
?? 2
. From
these readings and using the given formula thermal conductivity of the given bad conductor is calculated.










32

To find the thickness of the metallic disc (h) using screw gauge
Least count = 0.01mm Zero error = ? ???div
Zero correction = ? ???mm
Sl.No.
PSR
(x10
-3
m)
HSC
(div.)
TR = PSR + (HSC x LC)
(x10
-3
m)
Corrected reading
CR = TR ? ZC
(x10
-3
m)
1
2
3
4
5

Mean, h = ------------------------------ x10
-3
m
To determine the rate of cooling of metallic disc:
Time
s
Temperature
o
C
Time
s
Temperature
o
C







33

CALCULATION:
Mass of the disc, m= ---------- x10
-3
kg
Specific heat capacity of the disc,c = 385 J kg
-1
K
-1
Rate of cooling at ?2,
????
????
= -------------- deg s
-1
Radius of the disc, r = ---------- x10
-2
m
Height of the disc, h = ---------- x10
-2
m
Thickness of the bad conductor, d = ---------- x10
-3 m
Temperature of steam, ?1 = ---------
o
C
Steady temperature of the disc, ?2 = -------------
o
C
Thermal conductivity,
? ?
? ? ? ?
1 1
2 1
2
2 2
2
? ?
? ?
?
?
?
?
?
?
?
?
?
? k Wm
h r r
h r d
dt
d
MS
K
? ? ?
?


= --------------------

= -------------------- Wm
-1
K
-1








34
















RESULT:
The thermal conductivity of the given bad conductor by Lee?s disc method, K = -------------- Wm
-1
K
-1







35





1. What is meant by thermal conductivity?
2. What is meant by Rate of cooling?
3. Does the value of thermal conductivity depend on the dimension of the specimen?
4. Is there any reason to take the specimen in the form of a disc?
5. Can this method be used for good conductors?
6. What is lee's disc method?
7. What are the differences between good conductor and bad conductor?
8. What are the methods used to determine thermal conductivity of bad conductor?
9. What is meant by steady temperature?
10. What is meant by specific heat capacity?

Viva ? voce
36




37


Exp. No. 5 ULTRASONIC INTERFEROMETER

AIM:
To determine the velocity of the ultrasonic waves in a given liquid and to find the compressibility of
the liquid using ultrasonic interferometer
APPARATUS REQUIRED:
Ultrasonic interferometer (high frequency) generator, measuring cell, the experimental liquid
and coaxial cables
FORMULA:
1) Velocity of the ultrasonic waves v = f ? ms
-1
where,
f ?frequency of the ultrasonic waves (Hz)
? ? wavelength of the ultrasonic waves in the liquid (m)

2) Compressibility of the liquid ? =
1
?? 2
?? m
2
N
-1
where
? ? density of the given liquid (kg m
-3
)
v? velocity of the ultrasonic waves with in the liquid (m s
-1
)
DESCRIPTION:
The interferometer consists of (i) high frequency generator and (ii) measuring cell. The high
frequency generator is used to excite the quartz plate fixed at the bottom of the measuring cell.
The exited quartz plate generates ultrasonic waves in the experimental liquid contained in the cell. A micro
ammeter is provided to observe the change in the current.
Two control knobs are also provided in the generator for the purpose of sensitivity regulation and also
adjustment. The measuring cell is a double walled cell to maintain constant temperature during

FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
2


PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science and fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems and use this knowledge to acquire
higher education.
2. Core competence
To train the students in Engineering Physics so as to apply their knowledge and training to compare,
and to analyze various engineering industrial problems for finding solutions.
3. Breadth
To provide relevant training and experience to bridge the gap between theoretical learning and
practice that enables them to find solutions for the real time problems in industry and to design products.
4. Professionalism
To inculcate professional and effective communication skills, leadership qualities and team spirit for
the students to make them multi-faceted personalities and develop their ability to relate engineering issues
to broader social context.
5. Lifelong learning/ethics
To demonstrate and practice ethical and professional responsibilities in the industry and society by
and large, through commitment and lifelong learning needed for successful professional career.





3


PROGRAMME OUTCOMES (POs)

a) To demonstrate and apply knowledge of Mathematics, Science and Engineering fundamentals in
Engineering physics
b) To determine the Moment of Inertia of given disc and Rigidity modulus of the given wire using
Torsional Pendulum
c) To determine Young?s modulus of a given bar using Non-Uniform bending
d) To utilize laser source and grating to estimate the wave length, particle size of given powder and
Numerical Aperture & acceptance angle of given optical fiber
e) To find the Thermal conductivity of a bad conductor using Lee?s Disc method
f) To Measure the velocity of ultrasonic wave in a liquid and compressibility of the liquid usingultrasonic
Interferometer
g) To determine the wavelength of Hg source using grating and spectrometer
h) To find the thickness of a thin wire using Air- wedge method
i) To participate and succeed in competitive exams and visualize and work on laboratory and
multidisciplinary tasks











4


BS 8161 ? PHYSICSLABORATORY
(Common to all branches of B.E. / B.TechProgrammes)
SYLLABUS


To introduce different experiments to test basic understanding of physics concepts applied in optics, thermal
physics, properties of matter and liquids.

LIST OF EXPERIMENTS: PHYSICS LABORATORY(Any 5 Experiments)
1. Determination of Rigidity modulus ? Torsion pendulum
2. Determination of Young? s modulus by Non uniform bending method
3. (a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
4. Determination of thermal conductivity of a bad conductor ? Lee?s Disc method.
5. Determination of velocity of sound and compressibility of liquid ? Ultrasonic interferometer
6. Determination of wavelength of mercury spectrum ? spectrometer grating
7. Determination of band gap of a semiconductor
8. Determination of thickness of a thin wire ? Air wedge method




Completion of the course, the students will be able to: apply physics principles of optics and thermal physics
to evaluate engineering properties of materials.


COURSE OUTCOMES
COURSE OBJECTIVES
5

BS 8161 ? PHYSICS LABORATORY
CONTENTS

Sl.No. Name of the Experiment (any 5 experiments)
Page
No.
1.
Determination of Rigidity modulus ? Torsion pendulum
6
2.
Determination of Young ?s modulus by Non uniform bending method
12
3.
(a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
18
4.
Determination of thermal conductivity of a bad conductor ? Lee ?s Disc method.
28
5.
Determination of velocity of sound and compressibility of liquid ? Ultrasonic
interferometer
37
6.
Determination of wavelength of mercury spectrum ? spectrometer grating
42
7.
Determination of thickness of a thin wire ? Air wedge method
48
MEASURING INSTRUMENTS
M1 Screw gauge 54
M2 Vernier Calipers 58
M3 Travelling Microscope 62
M4 Spectrometer 66








6

TORSIONAL PENDULUM










7

Expt. No.1 TORSIONAL PENDULUM

AIM:
To determine the moment of inertia of the given disc and hence to determine the rigidity modulus of
the material of the given suspension wire by torsional oscillations
APPARATUS REQUIRED:
Torsional pendulum, two equal masses, stop clock, screw gauge and meter scale

FORMULA:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
where
m ?mass of the cylinder placed on the disc (kg)
To ?period of the pendulum for a length of l without mass (s)
T1?period of the pendulum for the same length when mass m is placed at a distance d 1
from the center of the suspension wire (s)
T2?period of the pendulum for the same length when mass m is placed at a distance d 2
from the center of the suspension wire (s)
a ? radius of the suspension wire (m)




8

1. To determine the time period of the disc:
Length of the wire (l)= --------
2
10
?
? m
Position of the equal
masses
Time for 10 oscillations Time period
(one oscillation)
s
Trial-1
s
Trial-2
s
Mean
s
Without any masses T0
With masses at
d1 = x10
-2
m
T1
With masses at
d2 = x10
-2
m
T2

2. To determine the radius of the wire:
Least count =0 .01 mm. Zero Error ZE = --------- divisions
Zero Correction ZC = ---------- mm

Sl.No.
Pitch Scale
Reading
PSR
3
10
?
? m
Head Scale
Coincidence
HSC
div
Observed reading
OR = PSR + (HSCXLC)
3
10
?
? m
Correct reading
CR = OR ? ZC
3
10
?
? m




Mean = ----------------
3
10
?
? m



9

PROCEDURE:
Torsional pendulum is suspended from vertical chuck. The length of the suspension wire is measured
between the vertical chuck and the chuck attached to the uniform circular disc (i). The circular disc is twisted
slightly without masses on the disc. Now it executes torsional oscillations. Care is taken to see that the disc
oscillates without wobbling. Time taken for 20 oscillations is noted with the help of a stop clock. Two trials are
taken. The average of these two trial readings is calculated from which the period of oscillations is found out
as T0.
Two identical cylindrical masses each of mass m are symmetrically placed on the disc on either side
of the wire at a distance d from the center of the disc. As before the disc is gently twisted. Time taken for 20
oscillations is noted from which the period of oscillation is calculated as T1.
The cylindrical masses are placed at a distance d2 from the center and the experiment is repeated.
The mean time period of oscillations is calculated T2.
The diameter of the specimen wire is measured accurately with the help of the screw gauge, at
various places on the wire. The average diameter and hence the radius of the wire is calculated as r.
Moment of inertia and the rigidity modulus are determined by the substituting the value of m, T 0, T1, T2,
T3, and l in the formula.










10

CALCULATION:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2

Mass of cylindrical mass, m = ----------- ? 10
-3
kg
Closest distance of the mass from the centre of the suspension wire, d1 = ------------ ? 10
-2
m
Farthest distance of the mass from the centre of suspension wire, d2= ------------? 10
-2
m
Period of oscillation without mass, To = ------------- s
Period of oscillation with mass at d1, T1= ------------ s
Period of oscillation with mass at d2, T2 = ------------- s

Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
= --------------- kg m
2
= --------------- kg m
2

Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
Moment of inertia, I = ------------------ kg m
2
Length of the wire, l = ------------------- ? 10
-2
m
Time of oscillation, To = ------------------ s
Radius of the wire, a = ------------------- ? 10
-3
m
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
= ----------------------
Rigidity modulus, n = ------------------- Nm
-2
11









RESULT:
(i)
The moment of inertia of the given circular disc, I = --------------- kg m
2
(ii)
The rigidity modulus of the material of the given wire, n = -------------- Nm
-2




1. State Hooke?s law.
2. Define ?Rigidity modulus
3. Define ?Moment of inertia
4. What is meant by torsional oscillation?
5. What is period of oscillation?
6. What is meant by twisting couple?
7. Define ? Shearing stress
8. Define ? Shearing strain
9. What is the unit of rigidity modulus?
10. What are the applications of torsional pendulum?


Viva ? voce
12


Young?s Modulus ? Non Uniform Bending
To determine depression (y):
L.C =.001cm M = ___________
3
10
?
? kg

Sl.No

Load


3
10
?
?
k
g
Microscope reading
Mean

2
10
?
? m
Depression
y for M kg

2
10
?
? m
Loading Unloading
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
1 W
2 W+50
3 W+100
4 W+150
5 W+200
6 W+250

Mean (y) = ----------
2
10
?
? m





13

Expt. No.2 YOUNG?S MODULUS BY NON ? UNIFORM BENDING
AIM:
To determine the young?s modulus of the material of the given bar, by non-uniform bending method
APPARATUS REQUIRED:
Travelling microscope, wooden bar, knife- edge, weights hanger, slotted weight, vernier calipers,
screw gauge and pin
FORMULA:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Where,
g ? acceleration due to gravity (9.8 ms
-2
)
l ? length of the bar between two knife edges (m)
b ? breadth of the bar (m)
d ? thickness of the bar (m)
y ? depressiont in the scale reading due to the change of mass M (m)
PROCEDURE:
The given wooden bar, for which young?s modulus is to be determined, is paced symmetrically on the
two knife edges. The distance between the knife edges is measured as the length of the bar (l). It is adjusted
to be, say, 60 cm. the weight hanger is suspended at the centre of the bar. A pin is held vertically at the
centre of the bar with the help of wax.
The given bar is brought to elastic mood by loading and unloading the bar with slotted weights in steps
of 50 g. This is repeated for two or three times. With the hanger as dead load W, the microscope is focused on
to the tip of the pin. The tangential screw of the microscope is adjusted so that the image of the tip of the pin
just touches the horizontal cross wire of the eyepiece. The main scale reading and the vernier scale
coincidence corresponding to this position are noted.
14

To find the breadth using vernier calipers, b:
Least count = ---------- cm Zero error = --------- div.
= ---------- ?10
-2
m Zero correction = ?ZE ?LC= --------- ?10
-2
m
Sl. No.

MSR
x 10
-2
m

VSC
div.
Observed reading
OR = MSR+(VSC ? LC)
x 10
-2
m
Correct Reading
CR = OR ? ZC
x 10
-2
m
1.

2.

3.


Mean, b = ------------------------?10
-2
m
To find the thickness using screw gauge, d:
Least count = ---------- mm Zero error = --------- div.
= ---------- ?10
-3
m Zero correction =ZE ?LC= --------- ?10
-3
m
Sl. No.

PSR
x 10
-3
m

HSC
div.
Observed reading
OR = PSR+ (HSC ? LC)
x 10
-3
m
Correct Reading
CR = OR ? ZC
x 10
-3
m
1.

2.

3.


Mean, d = ---------------------------?10
-3
m
15


The experiment is repeated by adding weights in steps of 50 g and every time the microscope is
adjusted for coincidence. The corresponding readings are noted. The experiment is repeated by unloading the
weights in steps of 50 g and the corresponding readings are tabulated. From this table, the shift in the scale
reading, say y, for a change of mass M is found out.
The breadth of the bar is measured at various points with the help of vernier calipers. Similarly the
thickness of the bar is measured by screw gauge. Substituting the values of M, y, l, d, b and g in the formula,
the young?s modulus of the material of the given bar is calculated.

















16

CALCULATION:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Acceleration due to gravity, g = 9.8 ms
-2
Length of the bar between two knife edges, l = ------------ ?10
-2
m
Breadth of the bar, b = ----------- ?10
-2
m
Thickness of the bar, d = ----------- ?10
-3
m
y = -----------?10
-2
m
E =
???? ?? 2
4?? ?? 3
?? Nm
-2

= ---------------
Young?s modulus, E = ----------- Nm
-2












17








RESULT:
Young?s modulus of the material of the given bar, E = ---------- Nm
-2


1. Define ? Young?s modulus
2. What is meant by Non-uniform bending?
3. Define ? Stress and strain
4. State Hooke?s law.
5. Define ? Neutral axis
6. What is the SI unit of young?s modulus?
7. Define ? Elastic limit
8. Define ? Elasticity
9. What are the factors affecting elasticity?
10. Define ? Elastic fatigue

Viva ? voce
18


To find the wavelength of the laser beam, ?:
Distance between the screen and the grating, D = ------------?10
-2
m
Number of lines per meter length of the grating, N = --------------- Lines per meter
Sl. No.
Order of diffraction,
(m)
Reading of the diffracted image
(?10
-2
m)
?? ?? = ?????? ?1
(
?? ?? ?? )
(deg.)
? =
?????? ?? ?? ????
m

Left side
(xi)
Right side
(xr)
Mean
(xm)










Mean, ? = ---------------- m


19

Expt. No.3(a) WAVELENGTH OF LASER LIGHT AND PARTICLE SIZE


AIM:
(i) To determine the wavelength of the given laser light.
(ii) To determine size of the given particle.
APPARATUS REQUIRED:
Diode laser, grating, screen, given micro particles, scale and screen.
FORMULAE:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
(ii) Grain size or diameter of the grain, 2d =
?????? ?? ?? m
Where
?? ?? ?angle of diffraction (deg.)
M ?order of diffraction (No unit)
N ?number of lines per metre length of the grating (m
-3
)
n ? order of diffraction (no unit)
? ? wavelength of laser light used (m)
D ? distance between the glass plate and the screen (m)
?? ?? - distance between the central bright spot and the nth fringe (m)
PROCEDURE:
TO FIND THE WAVELENGTH OF THE GIVEN LASER LIGHT:
The laser source, grating and screen are placed properly as shown in figure. The diode laser is kept
horizontally and switched on. Extreme care should be taken to avoid direct exposure of laser light on eyes.
20











21

The grating is held normal to the laser beam by adjusting the grating in such a way that the reflected
laser beam from the grating coincides with incident laser beam. Now the diffracted laser spots of various
orders can be seen on the screen, placed on the other side of the grating.

The distance of the different orders on either side of the central spot are measured as x randxi and are
tabulated.The mean value of xrandxiare calculated as xm for the m
th
order diffracted light. The distance
between the grating and the screen is measured as D. Hence, the angle of diffraction for the m
th
order,
?? ?? = ?????? ?1
(
?? ?? ?? )
The experiment is repeated for different orders and the readings are tabulated. From the table, ? for
each order is calculated. Substituting the value of ?, the corresponding order of diffraction and the number of
lines per meter length of the grating, the wavelength is calculated.

TO FIND THE SIZE OF THE GIVEN MICRO PARTICLE:

The lycopodium powder having fine micro particles of nearly same size is sprinkled on a glass plate.
This glass plate is kept between laser source and screen.
Now the particles present in the glass plate diffract laser beam from the source. By adjusting the
distance between the glass plate and the screen, a circular fringe pattern is obtained on the screen with
different orders of fingers. Now distance between the screen and the glass plate (D) is measured.
The distance of the first order and the second order fringe from the centre of spot are also measured.
Using the formula, the particle size is found out. The experiment is repeated for different D values.
22

To find the size of the particle:

CALCULATION:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
Number of lines per metre in the grating, N = ------------ lines per metre.
First order, m1; ?? 1
= ------------
Wavelength, ? =
?????? ?? 1
????
= ------------
Second order, m2; ?? 2
= ------------
Wavelength, ? =
?????? ?? 2
????
= ------------
Third order, m3; ?? 3
= ------------
Wavelength, ? =
?????? ?? 3
????
= ------------
Fourth order, m4; ?? 4
= ------------
Wavelength, ? =
?????? ?? 4
????
= -------------
Fifth order, m5; ?? 5
= ------------

Sl.No



Distance between
screen and glass
plate(D)
2
10
?
? m
Order of
diffraction
(n)
Distance between the
central bright spot and n
th

fringe (xn )
2
10
?
? m
Particle size
2
n
nD
d
x
?
?
m






23

Wavelength, ? =
?????? ?? 4
????
= ------------
Mean wavelength of the given laser light, ? = -------------- m
(ii) Grain size or diameter of the grain. 2d =
?????? ?? ??
Order of differaction, n = --------------
Wavelength of laser light used, ? = ------------- m
Distance between glass plate and the screen, D = ------------ m
Distance between central bright spot and the n
th
fringe,?? ?? = ------------ m
2d =
?????? ?? ??
=
= ------------ m








RESULT:
(i) Wavelength of the laser beam, ? = -------------- m
(ii) Average size of the particle = --------------- m

24


Optical fiber

To find numerical aperture, NA:

Sl. No.
Diameter of the circular patch
D(m)
Distance between the tip of the
fiber and the screen X (m)
NA =
?? (4?? 2
+?? 2
)
1
2





Mean NA =
Therefore, the acceptance angle, ? = Sin
-1
(NA) = -------------------
= -------------------


25

Expt. No.3(b) NUMERICAL APERTURE AND ACCEPTANCE ANGLE
AIM:
To measure the numerical aperture and the acceptance angle of the given fiber cable
APPARATUS REQUIRED:
Optical fiber cable with source, NA jig and in-line adaptor
FORMULA:
The numerical aperture, NA =
?? (4?? 2
+?? 2
)
1
2

Acceptance angle, ? = Sin
-1
(NA)
where,
D ? diameter of the circular patch (m)
X ? distance between the tip of the fiber and the screen (m)
PROCEDURE:
One end of the one metre fiber cable is connected to the laser light source and the other end
to the NA jig as shown in figure. The AC main is plugged in and the laser light is adjusted so that it appears at
the end of the fiber on the NA jig, the intensity knob is adjusted to get maximum intensity.
The white screen with the four concentric circles (10 mm, 20 mm, 30 mm and 40 mm diameter) is held
vertically at a suitable distance to make the red spot from the emitting fiber coincides with the 10 mm circle,
the diameter (D) of the spot is noted. The distance (X) of the screen from the fiber end is recorded.
The procedure is repeated for 20 mm, 30 mm, 40 mm diameter circles and the readings are tabulated.




26

















RESULT:
The numerical aperture, NA = ----------------
Acceptance angle, ? = ----------------




27




1. What is semiconductor diode laser?
2. What is meant by active material in laser?
3. What is meant by LASER?
4. What is stimulated emission?
5. What are the characteristics of laser radiation?
6. What is homo?junction laser?
7. What is hetero?junction laser?
8. What are the applications of semiconductor laser?
9. What are the conditions required for laser action?
10. Define ? Numerical aperture







Viva ? voce
28


Lee?s disc setup


29

Expt. No. 4 THERMAL CONDUCTIVITY OF A BAD CONDUCTOR
BY LEE?S DISC METHOD

AIM:
To determine the coefficient of thermal conductivity of a bad conductor
APPARATUS REQUIRED:
Lee?s disc apparatus, bad conductors, stop-clock, thermometers, screw gauge, vernier calipers and
steam boiler
FORMULA:
Thermal conductivity of a bad conductor,
? ?
? ? ? ?
1 1
2 1
2
2 2
2
? ?
? ?
?
?
?
?
?
?
?
?
?
? k Wm
h r r
h r d
dt
d
MS
K
? ? ?
?

M ? Mass of the metallic disc (Kg)
S ? Specific heat capacity of the metallic disc ( J Kg
-1
K
-1
)
? rate of cooling at steady temperature (
o
C/s)
d ? thickness of the bad conductor (m)
h ? thickness of the metallic disc (m)
r?radius of the metallic disc (m)
1
? ? steady temperature of the steam chamber (
o
C)
2
? ? steady temperature of the Metallic disc (
o
C)

PROCEDURE:
The thickness of the bad conductor say card board and thickness of the metallic disc are determined
using a screw gauge. The radius of the metallic disc is found using a vernier caliper. The mass of a metallic
disc is also found using a common balance. The readings are tabulated.

30

To find the radius of the metallic disc (r) using Vernier Calipers
Least count = 0.01cm Zero error = ? ???div
Zero correction = ? ???cm
= --------- ?10
-2
m
Sl.No.
MSR
(x10
-2
m)
VSC
(div.)
OR = MSR +(VSC x LC)
(x10
-2
m)
CR = OR ? ZC
(x10
-2
m)
1
2
3
4

Mean radius, r = --------------------------------- x10
-2
m
To find the thickness of the bad conductor (d) using Screw gauge
Least count = 0.01mm Zero error = ? ???div
Zero correction = ? ???mm
Sl.No.
PSR
(x10
-3
m)
HSC
(div.)
OR = PSR + (HSC x LC)
(x10
-3
m)
CR = OR ? ZC
(x10
-3
m)
1.
2.
3.
4.

Mean, d = -------------------------------- x10
-3
m
31

The whole Lee?s disc apparatus is suspended from a stand as shown in the figure. The given bad
conductor is placed in between the metallic disc and the steam chamber. Two thermometers T1 and T2 are
inserted into the respective holes.
Steam from the steam boiler is passed into the steam chamber until the temperature of the steam
chamber and the metallic disc are steady. The Steady temperature (?1) of the steam chamber and (?2) of the
metallic disc recorded by the thermometers are noted.
Now the bad conductor is removed and the steam chamber is placed in direct contact with the metallic
disc. The temperature of the disc rapidly rises. When the temperature of the disc rises about 10
o
Cabove
?2
o
C, the steam chamber is carefully removed after cutting of the steam supply.
When the temperature of the disc reaches 10
o
C above the steady temperature of the disc i.e. (?2+
10)
o
C , stop clock is started. Time for every one degree celsius fall of temperature is noted until the metallic
disc attains a temperature (?2 - 10)
o
C.
A graph is drawn taking time along the x-axis and temperature along the y-axis. The cooling curve is
obtained .To obtain the rate of the cooling (
????
????
)
?? 2
from this graph, a triangle is drawn by taking 1
o
C above
and 1
o
Cbelow the steady temperature ?2. Then the slope AB / BC gives the rate of cooling at(
????
????
)
?? 2
. From
these readings and using the given formula thermal conductivity of the given bad conductor is calculated.










32

To find the thickness of the metallic disc (h) using screw gauge
Least count = 0.01mm Zero error = ? ???div
Zero correction = ? ???mm
Sl.No.
PSR
(x10
-3
m)
HSC
(div.)
TR = PSR + (HSC x LC)
(x10
-3
m)
Corrected reading
CR = TR ? ZC
(x10
-3
m)
1
2
3
4
5

Mean, h = ------------------------------ x10
-3
m
To determine the rate of cooling of metallic disc:
Time
s
Temperature
o
C
Time
s
Temperature
o
C







33

CALCULATION:
Mass of the disc, m= ---------- x10
-3
kg
Specific heat capacity of the disc,c = 385 J kg
-1
K
-1
Rate of cooling at ?2,
????
????
= -------------- deg s
-1
Radius of the disc, r = ---------- x10
-2
m
Height of the disc, h = ---------- x10
-2
m
Thickness of the bad conductor, d = ---------- x10
-3 m
Temperature of steam, ?1 = ---------
o
C
Steady temperature of the disc, ?2 = -------------
o
C
Thermal conductivity,
? ?
? ? ? ?
1 1
2 1
2
2 2
2
? ?
? ?
?
?
?
?
?
?
?
?
?
? k Wm
h r r
h r d
dt
d
MS
K
? ? ?
?


= --------------------

= -------------------- Wm
-1
K
-1








34
















RESULT:
The thermal conductivity of the given bad conductor by Lee?s disc method, K = -------------- Wm
-1
K
-1







35





1. What is meant by thermal conductivity?
2. What is meant by Rate of cooling?
3. Does the value of thermal conductivity depend on the dimension of the specimen?
4. Is there any reason to take the specimen in the form of a disc?
5. Can this method be used for good conductors?
6. What is lee's disc method?
7. What are the differences between good conductor and bad conductor?
8. What are the methods used to determine thermal conductivity of bad conductor?
9. What is meant by steady temperature?
10. What is meant by specific heat capacity?

Viva ? voce
36




37


Exp. No. 5 ULTRASONIC INTERFEROMETER

AIM:
To determine the velocity of the ultrasonic waves in a given liquid and to find the compressibility of
the liquid using ultrasonic interferometer
APPARATUS REQUIRED:
Ultrasonic interferometer (high frequency) generator, measuring cell, the experimental liquid
and coaxial cables
FORMULA:
1) Velocity of the ultrasonic waves v = f ? ms
-1
where,
f ?frequency of the ultrasonic waves (Hz)
? ? wavelength of the ultrasonic waves in the liquid (m)

2) Compressibility of the liquid ? =
1
?? 2
?? m
2
N
-1
where
? ? density of the given liquid (kg m
-3
)
v? velocity of the ultrasonic waves with in the liquid (m s
-1
)
DESCRIPTION:
The interferometer consists of (i) high frequency generator and (ii) measuring cell. The high
frequency generator is used to excite the quartz plate fixed at the bottom of the measuring cell.
The exited quartz plate generates ultrasonic waves in the experimental liquid contained in the cell. A micro
ammeter is provided to observe the change in the current.
Two control knobs are also provided in the generator for the purpose of sensitivity regulation and also
adjustment. The measuring cell is a double walled cell to maintain constant temperature during

38


To find the wavelength of the ultrasonic waves in the liquid:

Order of
maximum current

Micrometer reading
Distance for n
maximum current, d
(x10
-3
m)
Wavelength
?=2d/n
(x10
-3
m)
PSR
(x10
-3
m)
HSR
(div)
TR
(x10
-3
m)

x
x+n
x+2n
x+3n



Wavelength, ? = ------------------ x10
-3
m
Frequency of ultrasonic waves = 2 MHz

CALCULATION:
1) The Velocity of the ultrasonic waves, v = f?
= ---------- m s
-1
The density of the given liquid ? = ---------- kg m
-3
2) Adiabatic compressibility of the liquid, ? =
1
?? 2
??
= -----------
Adiabatic compressibility of the liquid, ? = --------------


FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
2


PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science and fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems and use this knowledge to acquire
higher education.
2. Core competence
To train the students in Engineering Physics so as to apply their knowledge and training to compare,
and to analyze various engineering industrial problems for finding solutions.
3. Breadth
To provide relevant training and experience to bridge the gap between theoretical learning and
practice that enables them to find solutions for the real time problems in industry and to design products.
4. Professionalism
To inculcate professional and effective communication skills, leadership qualities and team spirit for
the students to make them multi-faceted personalities and develop their ability to relate engineering issues
to broader social context.
5. Lifelong learning/ethics
To demonstrate and practice ethical and professional responsibilities in the industry and society by
and large, through commitment and lifelong learning needed for successful professional career.





3


PROGRAMME OUTCOMES (POs)

a) To demonstrate and apply knowledge of Mathematics, Science and Engineering fundamentals in
Engineering physics
b) To determine the Moment of Inertia of given disc and Rigidity modulus of the given wire using
Torsional Pendulum
c) To determine Young?s modulus of a given bar using Non-Uniform bending
d) To utilize laser source and grating to estimate the wave length, particle size of given powder and
Numerical Aperture & acceptance angle of given optical fiber
e) To find the Thermal conductivity of a bad conductor using Lee?s Disc method
f) To Measure the velocity of ultrasonic wave in a liquid and compressibility of the liquid usingultrasonic
Interferometer
g) To determine the wavelength of Hg source using grating and spectrometer
h) To find the thickness of a thin wire using Air- wedge method
i) To participate and succeed in competitive exams and visualize and work on laboratory and
multidisciplinary tasks











4


BS 8161 ? PHYSICSLABORATORY
(Common to all branches of B.E. / B.TechProgrammes)
SYLLABUS


To introduce different experiments to test basic understanding of physics concepts applied in optics, thermal
physics, properties of matter and liquids.

LIST OF EXPERIMENTS: PHYSICS LABORATORY(Any 5 Experiments)
1. Determination of Rigidity modulus ? Torsion pendulum
2. Determination of Young? s modulus by Non uniform bending method
3. (a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
4. Determination of thermal conductivity of a bad conductor ? Lee?s Disc method.
5. Determination of velocity of sound and compressibility of liquid ? Ultrasonic interferometer
6. Determination of wavelength of mercury spectrum ? spectrometer grating
7. Determination of band gap of a semiconductor
8. Determination of thickness of a thin wire ? Air wedge method




Completion of the course, the students will be able to: apply physics principles of optics and thermal physics
to evaluate engineering properties of materials.


COURSE OUTCOMES
COURSE OBJECTIVES
5

BS 8161 ? PHYSICS LABORATORY
CONTENTS

Sl.No. Name of the Experiment (any 5 experiments)
Page
No.
1.
Determination of Rigidity modulus ? Torsion pendulum
6
2.
Determination of Young ?s modulus by Non uniform bending method
12
3.
(a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
18
4.
Determination of thermal conductivity of a bad conductor ? Lee ?s Disc method.
28
5.
Determination of velocity of sound and compressibility of liquid ? Ultrasonic
interferometer
37
6.
Determination of wavelength of mercury spectrum ? spectrometer grating
42
7.
Determination of thickness of a thin wire ? Air wedge method
48
MEASURING INSTRUMENTS
M1 Screw gauge 54
M2 Vernier Calipers 58
M3 Travelling Microscope 62
M4 Spectrometer 66








6

TORSIONAL PENDULUM










7

Expt. No.1 TORSIONAL PENDULUM

AIM:
To determine the moment of inertia of the given disc and hence to determine the rigidity modulus of
the material of the given suspension wire by torsional oscillations
APPARATUS REQUIRED:
Torsional pendulum, two equal masses, stop clock, screw gauge and meter scale

FORMULA:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
where
m ?mass of the cylinder placed on the disc (kg)
To ?period of the pendulum for a length of l without mass (s)
T1?period of the pendulum for the same length when mass m is placed at a distance d 1
from the center of the suspension wire (s)
T2?period of the pendulum for the same length when mass m is placed at a distance d 2
from the center of the suspension wire (s)
a ? radius of the suspension wire (m)




8

1. To determine the time period of the disc:
Length of the wire (l)= --------
2
10
?
? m
Position of the equal
masses
Time for 10 oscillations Time period
(one oscillation)
s
Trial-1
s
Trial-2
s
Mean
s
Without any masses T0
With masses at
d1 = x10
-2
m
T1
With masses at
d2 = x10
-2
m
T2

2. To determine the radius of the wire:
Least count =0 .01 mm. Zero Error ZE = --------- divisions
Zero Correction ZC = ---------- mm

Sl.No.
Pitch Scale
Reading
PSR
3
10
?
? m
Head Scale
Coincidence
HSC
div
Observed reading
OR = PSR + (HSCXLC)
3
10
?
? m
Correct reading
CR = OR ? ZC
3
10
?
? m




Mean = ----------------
3
10
?
? m



9

PROCEDURE:
Torsional pendulum is suspended from vertical chuck. The length of the suspension wire is measured
between the vertical chuck and the chuck attached to the uniform circular disc (i). The circular disc is twisted
slightly without masses on the disc. Now it executes torsional oscillations. Care is taken to see that the disc
oscillates without wobbling. Time taken for 20 oscillations is noted with the help of a stop clock. Two trials are
taken. The average of these two trial readings is calculated from which the period of oscillations is found out
as T0.
Two identical cylindrical masses each of mass m are symmetrically placed on the disc on either side
of the wire at a distance d from the center of the disc. As before the disc is gently twisted. Time taken for 20
oscillations is noted from which the period of oscillation is calculated as T1.
The cylindrical masses are placed at a distance d2 from the center and the experiment is repeated.
The mean time period of oscillations is calculated T2.
The diameter of the specimen wire is measured accurately with the help of the screw gauge, at
various places on the wire. The average diameter and hence the radius of the wire is calculated as r.
Moment of inertia and the rigidity modulus are determined by the substituting the value of m, T 0, T1, T2,
T3, and l in the formula.










10

CALCULATION:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2

Mass of cylindrical mass, m = ----------- ? 10
-3
kg
Closest distance of the mass from the centre of the suspension wire, d1 = ------------ ? 10
-2
m
Farthest distance of the mass from the centre of suspension wire, d2= ------------? 10
-2
m
Period of oscillation without mass, To = ------------- s
Period of oscillation with mass at d1, T1= ------------ s
Period of oscillation with mass at d2, T2 = ------------- s

Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
= --------------- kg m
2
= --------------- kg m
2

Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
Moment of inertia, I = ------------------ kg m
2
Length of the wire, l = ------------------- ? 10
-2
m
Time of oscillation, To = ------------------ s
Radius of the wire, a = ------------------- ? 10
-3
m
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
= ----------------------
Rigidity modulus, n = ------------------- Nm
-2
11









RESULT:
(i)
The moment of inertia of the given circular disc, I = --------------- kg m
2
(ii)
The rigidity modulus of the material of the given wire, n = -------------- Nm
-2




1. State Hooke?s law.
2. Define ?Rigidity modulus
3. Define ?Moment of inertia
4. What is meant by torsional oscillation?
5. What is period of oscillation?
6. What is meant by twisting couple?
7. Define ? Shearing stress
8. Define ? Shearing strain
9. What is the unit of rigidity modulus?
10. What are the applications of torsional pendulum?


Viva ? voce
12


Young?s Modulus ? Non Uniform Bending
To determine depression (y):
L.C =.001cm M = ___________
3
10
?
? kg

Sl.No

Load


3
10
?
?
k
g
Microscope reading
Mean

2
10
?
? m
Depression
y for M kg

2
10
?
? m
Loading Unloading
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
1 W
2 W+50
3 W+100
4 W+150
5 W+200
6 W+250

Mean (y) = ----------
2
10
?
? m





13

Expt. No.2 YOUNG?S MODULUS BY NON ? UNIFORM BENDING
AIM:
To determine the young?s modulus of the material of the given bar, by non-uniform bending method
APPARATUS REQUIRED:
Travelling microscope, wooden bar, knife- edge, weights hanger, slotted weight, vernier calipers,
screw gauge and pin
FORMULA:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Where,
g ? acceleration due to gravity (9.8 ms
-2
)
l ? length of the bar between two knife edges (m)
b ? breadth of the bar (m)
d ? thickness of the bar (m)
y ? depressiont in the scale reading due to the change of mass M (m)
PROCEDURE:
The given wooden bar, for which young?s modulus is to be determined, is paced symmetrically on the
two knife edges. The distance between the knife edges is measured as the length of the bar (l). It is adjusted
to be, say, 60 cm. the weight hanger is suspended at the centre of the bar. A pin is held vertically at the
centre of the bar with the help of wax.
The given bar is brought to elastic mood by loading and unloading the bar with slotted weights in steps
of 50 g. This is repeated for two or three times. With the hanger as dead load W, the microscope is focused on
to the tip of the pin. The tangential screw of the microscope is adjusted so that the image of the tip of the pin
just touches the horizontal cross wire of the eyepiece. The main scale reading and the vernier scale
coincidence corresponding to this position are noted.
14

To find the breadth using vernier calipers, b:
Least count = ---------- cm Zero error = --------- div.
= ---------- ?10
-2
m Zero correction = ?ZE ?LC= --------- ?10
-2
m
Sl. No.

MSR
x 10
-2
m

VSC
div.
Observed reading
OR = MSR+(VSC ? LC)
x 10
-2
m
Correct Reading
CR = OR ? ZC
x 10
-2
m
1.

2.

3.


Mean, b = ------------------------?10
-2
m
To find the thickness using screw gauge, d:
Least count = ---------- mm Zero error = --------- div.
= ---------- ?10
-3
m Zero correction =ZE ?LC= --------- ?10
-3
m
Sl. No.

PSR
x 10
-3
m

HSC
div.
Observed reading
OR = PSR+ (HSC ? LC)
x 10
-3
m
Correct Reading
CR = OR ? ZC
x 10
-3
m
1.

2.

3.


Mean, d = ---------------------------?10
-3
m
15


The experiment is repeated by adding weights in steps of 50 g and every time the microscope is
adjusted for coincidence. The corresponding readings are noted. The experiment is repeated by unloading the
weights in steps of 50 g and the corresponding readings are tabulated. From this table, the shift in the scale
reading, say y, for a change of mass M is found out.
The breadth of the bar is measured at various points with the help of vernier calipers. Similarly the
thickness of the bar is measured by screw gauge. Substituting the values of M, y, l, d, b and g in the formula,
the young?s modulus of the material of the given bar is calculated.

















16

CALCULATION:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Acceleration due to gravity, g = 9.8 ms
-2
Length of the bar between two knife edges, l = ------------ ?10
-2
m
Breadth of the bar, b = ----------- ?10
-2
m
Thickness of the bar, d = ----------- ?10
-3
m
y = -----------?10
-2
m
E =
???? ?? 2
4?? ?? 3
?? Nm
-2

= ---------------
Young?s modulus, E = ----------- Nm
-2












17








RESULT:
Young?s modulus of the material of the given bar, E = ---------- Nm
-2


1. Define ? Young?s modulus
2. What is meant by Non-uniform bending?
3. Define ? Stress and strain
4. State Hooke?s law.
5. Define ? Neutral axis
6. What is the SI unit of young?s modulus?
7. Define ? Elastic limit
8. Define ? Elasticity
9. What are the factors affecting elasticity?
10. Define ? Elastic fatigue

Viva ? voce
18


To find the wavelength of the laser beam, ?:
Distance between the screen and the grating, D = ------------?10
-2
m
Number of lines per meter length of the grating, N = --------------- Lines per meter
Sl. No.
Order of diffraction,
(m)
Reading of the diffracted image
(?10
-2
m)
?? ?? = ?????? ?1
(
?? ?? ?? )
(deg.)
? =
?????? ?? ?? ????
m

Left side
(xi)
Right side
(xr)
Mean
(xm)










Mean, ? = ---------------- m


19

Expt. No.3(a) WAVELENGTH OF LASER LIGHT AND PARTICLE SIZE


AIM:
(i) To determine the wavelength of the given laser light.
(ii) To determine size of the given particle.
APPARATUS REQUIRED:
Diode laser, grating, screen, given micro particles, scale and screen.
FORMULAE:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
(ii) Grain size or diameter of the grain, 2d =
?????? ?? ?? m
Where
?? ?? ?angle of diffraction (deg.)
M ?order of diffraction (No unit)
N ?number of lines per metre length of the grating (m
-3
)
n ? order of diffraction (no unit)
? ? wavelength of laser light used (m)
D ? distance between the glass plate and the screen (m)
?? ?? - distance between the central bright spot and the nth fringe (m)
PROCEDURE:
TO FIND THE WAVELENGTH OF THE GIVEN LASER LIGHT:
The laser source, grating and screen are placed properly as shown in figure. The diode laser is kept
horizontally and switched on. Extreme care should be taken to avoid direct exposure of laser light on eyes.
20











21

The grating is held normal to the laser beam by adjusting the grating in such a way that the reflected
laser beam from the grating coincides with incident laser beam. Now the diffracted laser spots of various
orders can be seen on the screen, placed on the other side of the grating.

The distance of the different orders on either side of the central spot are measured as x randxi and are
tabulated.The mean value of xrandxiare calculated as xm for the m
th
order diffracted light. The distance
between the grating and the screen is measured as D. Hence, the angle of diffraction for the m
th
order,
?? ?? = ?????? ?1
(
?? ?? ?? )
The experiment is repeated for different orders and the readings are tabulated. From the table, ? for
each order is calculated. Substituting the value of ?, the corresponding order of diffraction and the number of
lines per meter length of the grating, the wavelength is calculated.

TO FIND THE SIZE OF THE GIVEN MICRO PARTICLE:

The lycopodium powder having fine micro particles of nearly same size is sprinkled on a glass plate.
This glass plate is kept between laser source and screen.
Now the particles present in the glass plate diffract laser beam from the source. By adjusting the
distance between the glass plate and the screen, a circular fringe pattern is obtained on the screen with
different orders of fingers. Now distance between the screen and the glass plate (D) is measured.
The distance of the first order and the second order fringe from the centre of spot are also measured.
Using the formula, the particle size is found out. The experiment is repeated for different D values.
22

To find the size of the particle:

CALCULATION:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
Number of lines per metre in the grating, N = ------------ lines per metre.
First order, m1; ?? 1
= ------------
Wavelength, ? =
?????? ?? 1
????
= ------------
Second order, m2; ?? 2
= ------------
Wavelength, ? =
?????? ?? 2
????
= ------------
Third order, m3; ?? 3
= ------------
Wavelength, ? =
?????? ?? 3
????
= ------------
Fourth order, m4; ?? 4
= ------------
Wavelength, ? =
?????? ?? 4
????
= -------------
Fifth order, m5; ?? 5
= ------------

Sl.No



Distance between
screen and glass
plate(D)
2
10
?
? m
Order of
diffraction
(n)
Distance between the
central bright spot and n
th

fringe (xn )
2
10
?
? m
Particle size
2
n
nD
d
x
?
?
m






23

Wavelength, ? =
?????? ?? 4
????
= ------------
Mean wavelength of the given laser light, ? = -------------- m
(ii) Grain size or diameter of the grain. 2d =
?????? ?? ??
Order of differaction, n = --------------
Wavelength of laser light used, ? = ------------- m
Distance between glass plate and the screen, D = ------------ m
Distance between central bright spot and the n
th
fringe,?? ?? = ------------ m
2d =
?????? ?? ??
=
= ------------ m








RESULT:
(i) Wavelength of the laser beam, ? = -------------- m
(ii) Average size of the particle = --------------- m

24


Optical fiber

To find numerical aperture, NA:

Sl. No.
Diameter of the circular patch
D(m)
Distance between the tip of the
fiber and the screen X (m)
NA =
?? (4?? 2
+?? 2
)
1
2





Mean NA =
Therefore, the acceptance angle, ? = Sin
-1
(NA) = -------------------
= -------------------


25

Expt. No.3(b) NUMERICAL APERTURE AND ACCEPTANCE ANGLE
AIM:
To measure the numerical aperture and the acceptance angle of the given fiber cable
APPARATUS REQUIRED:
Optical fiber cable with source, NA jig and in-line adaptor
FORMULA:
The numerical aperture, NA =
?? (4?? 2
+?? 2
)
1
2

Acceptance angle, ? = Sin
-1
(NA)
where,
D ? diameter of the circular patch (m)
X ? distance between the tip of the fiber and the screen (m)
PROCEDURE:
One end of the one metre fiber cable is connected to the laser light source and the other end
to the NA jig as shown in figure. The AC main is plugged in and the laser light is adjusted so that it appears at
the end of the fiber on the NA jig, the intensity knob is adjusted to get maximum intensity.
The white screen with the four concentric circles (10 mm, 20 mm, 30 mm and 40 mm diameter) is held
vertically at a suitable distance to make the red spot from the emitting fiber coincides with the 10 mm circle,
the diameter (D) of the spot is noted. The distance (X) of the screen from the fiber end is recorded.
The procedure is repeated for 20 mm, 30 mm, 40 mm diameter circles and the readings are tabulated.




26

















RESULT:
The numerical aperture, NA = ----------------
Acceptance angle, ? = ----------------




27




1. What is semiconductor diode laser?
2. What is meant by active material in laser?
3. What is meant by LASER?
4. What is stimulated emission?
5. What are the characteristics of laser radiation?
6. What is homo?junction laser?
7. What is hetero?junction laser?
8. What are the applications of semiconductor laser?
9. What are the conditions required for laser action?
10. Define ? Numerical aperture







Viva ? voce
28


Lee?s disc setup


29

Expt. No. 4 THERMAL CONDUCTIVITY OF A BAD CONDUCTOR
BY LEE?S DISC METHOD

AIM:
To determine the coefficient of thermal conductivity of a bad conductor
APPARATUS REQUIRED:
Lee?s disc apparatus, bad conductors, stop-clock, thermometers, screw gauge, vernier calipers and
steam boiler
FORMULA:
Thermal conductivity of a bad conductor,
? ?
? ? ? ?
1 1
2 1
2
2 2
2
? ?
? ?
?
?
?
?
?
?
?
?
?
? k Wm
h r r
h r d
dt
d
MS
K
? ? ?
?

M ? Mass of the metallic disc (Kg)
S ? Specific heat capacity of the metallic disc ( J Kg
-1
K
-1
)
? rate of cooling at steady temperature (
o
C/s)
d ? thickness of the bad conductor (m)
h ? thickness of the metallic disc (m)
r?radius of the metallic disc (m)
1
? ? steady temperature of the steam chamber (
o
C)
2
? ? steady temperature of the Metallic disc (
o
C)

PROCEDURE:
The thickness of the bad conductor say card board and thickness of the metallic disc are determined
using a screw gauge. The radius of the metallic disc is found using a vernier caliper. The mass of a metallic
disc is also found using a common balance. The readings are tabulated.

30

To find the radius of the metallic disc (r) using Vernier Calipers
Least count = 0.01cm Zero error = ? ???div
Zero correction = ? ???cm
= --------- ?10
-2
m
Sl.No.
MSR
(x10
-2
m)
VSC
(div.)
OR = MSR +(VSC x LC)
(x10
-2
m)
CR = OR ? ZC
(x10
-2
m)
1
2
3
4

Mean radius, r = --------------------------------- x10
-2
m
To find the thickness of the bad conductor (d) using Screw gauge
Least count = 0.01mm Zero error = ? ???div
Zero correction = ? ???mm
Sl.No.
PSR
(x10
-3
m)
HSC
(div.)
OR = PSR + (HSC x LC)
(x10
-3
m)
CR = OR ? ZC
(x10
-3
m)
1.
2.
3.
4.

Mean, d = -------------------------------- x10
-3
m
31

The whole Lee?s disc apparatus is suspended from a stand as shown in the figure. The given bad
conductor is placed in between the metallic disc and the steam chamber. Two thermometers T1 and T2 are
inserted into the respective holes.
Steam from the steam boiler is passed into the steam chamber until the temperature of the steam
chamber and the metallic disc are steady. The Steady temperature (?1) of the steam chamber and (?2) of the
metallic disc recorded by the thermometers are noted.
Now the bad conductor is removed and the steam chamber is placed in direct contact with the metallic
disc. The temperature of the disc rapidly rises. When the temperature of the disc rises about 10
o
Cabove
?2
o
C, the steam chamber is carefully removed after cutting of the steam supply.
When the temperature of the disc reaches 10
o
C above the steady temperature of the disc i.e. (?2+
10)
o
C , stop clock is started. Time for every one degree celsius fall of temperature is noted until the metallic
disc attains a temperature (?2 - 10)
o
C.
A graph is drawn taking time along the x-axis and temperature along the y-axis. The cooling curve is
obtained .To obtain the rate of the cooling (
????
????
)
?? 2
from this graph, a triangle is drawn by taking 1
o
C above
and 1
o
Cbelow the steady temperature ?2. Then the slope AB / BC gives the rate of cooling at(
????
????
)
?? 2
. From
these readings and using the given formula thermal conductivity of the given bad conductor is calculated.










32

To find the thickness of the metallic disc (h) using screw gauge
Least count = 0.01mm Zero error = ? ???div
Zero correction = ? ???mm
Sl.No.
PSR
(x10
-3
m)
HSC
(div.)
TR = PSR + (HSC x LC)
(x10
-3
m)
Corrected reading
CR = TR ? ZC
(x10
-3
m)
1
2
3
4
5

Mean, h = ------------------------------ x10
-3
m
To determine the rate of cooling of metallic disc:
Time
s
Temperature
o
C
Time
s
Temperature
o
C







33

CALCULATION:
Mass of the disc, m= ---------- x10
-3
kg
Specific heat capacity of the disc,c = 385 J kg
-1
K
-1
Rate of cooling at ?2,
????
????
= -------------- deg s
-1
Radius of the disc, r = ---------- x10
-2
m
Height of the disc, h = ---------- x10
-2
m
Thickness of the bad conductor, d = ---------- x10
-3 m
Temperature of steam, ?1 = ---------
o
C
Steady temperature of the disc, ?2 = -------------
o
C
Thermal conductivity,
? ?
? ? ? ?
1 1
2 1
2
2 2
2
? ?
? ?
?
?
?
?
?
?
?
?
?
? k Wm
h r r
h r d
dt
d
MS
K
? ? ?
?


= --------------------

= -------------------- Wm
-1
K
-1








34
















RESULT:
The thermal conductivity of the given bad conductor by Lee?s disc method, K = -------------- Wm
-1
K
-1







35





1. What is meant by thermal conductivity?
2. What is meant by Rate of cooling?
3. Does the value of thermal conductivity depend on the dimension of the specimen?
4. Is there any reason to take the specimen in the form of a disc?
5. Can this method be used for good conductors?
6. What is lee's disc method?
7. What are the differences between good conductor and bad conductor?
8. What are the methods used to determine thermal conductivity of bad conductor?
9. What is meant by steady temperature?
10. What is meant by specific heat capacity?

Viva ? voce
36




37


Exp. No. 5 ULTRASONIC INTERFEROMETER

AIM:
To determine the velocity of the ultrasonic waves in a given liquid and to find the compressibility of
the liquid using ultrasonic interferometer
APPARATUS REQUIRED:
Ultrasonic interferometer (high frequency) generator, measuring cell, the experimental liquid
and coaxial cables
FORMULA:
1) Velocity of the ultrasonic waves v = f ? ms
-1
where,
f ?frequency of the ultrasonic waves (Hz)
? ? wavelength of the ultrasonic waves in the liquid (m)

2) Compressibility of the liquid ? =
1
?? 2
?? m
2
N
-1
where
? ? density of the given liquid (kg m
-3
)
v? velocity of the ultrasonic waves with in the liquid (m s
-1
)
DESCRIPTION:
The interferometer consists of (i) high frequency generator and (ii) measuring cell. The high
frequency generator is used to excite the quartz plate fixed at the bottom of the measuring cell.
The exited quartz plate generates ultrasonic waves in the experimental liquid contained in the cell. A micro
ammeter is provided to observe the change in the current.
Two control knobs are also provided in the generator for the purpose of sensitivity regulation and also
adjustment. The measuring cell is a double walled cell to maintain constant temperature during

38


To find the wavelength of the ultrasonic waves in the liquid:

Order of
maximum current

Micrometer reading
Distance for n
maximum current, d
(x10
-3
m)
Wavelength
?=2d/n
(x10
-3
m)
PSR
(x10
-3
m)
HSR
(div)
TR
(x10
-3
m)

x
x+n
x+2n
x+3n



Wavelength, ? = ------------------ x10
-3
m
Frequency of ultrasonic waves = 2 MHz

CALCULATION:
1) The Velocity of the ultrasonic waves, v = f?
= ---------- m s
-1
The density of the given liquid ? = ---------- kg m
-3
2) Adiabatic compressibility of the liquid, ? =
1
?? 2
??
= -----------
Adiabatic compressibility of the liquid, ? = --------------


39

experiment.A fine micrometer arrangement is fixed at the top of the interferometer, enables the reflector
pates to move upward or downward through a known distance.
PRINCIPLE:
The velocity of the ultrasonic waves is determined using the interferometer. The principle used in the
measurement of velocity is based on the accurate determination of the wave length (?) of ultrasonic waves
in the liquid. The ultrasonic waves are reflected back by a removable metallic plate parallel to the crystal
.These two ultrasonic waves superimpose producing stationary wave pattern within the medium.

If the separation between these two plates is exactly an integral multiple of ?/2 of the ultrasonic
waves, acoustic resonance is produced in the standing waves.

This acoustic resonance gives rise to an electrical reaction on the generator and the anode current of the
generator becomes maximum.
PROCEDURE:
The measuring cell is connected to the output terminal of the high frequency generator through a
shielded cable. The cell is filled with an experimental liquid before switching on the generator. The
ultrasonic waves move normally from the quartz crystal till they are reflected back from the movable plate
and the standing waves are formed in the liquid in between the reflector plate and the quartz crystal.
The micrometer is slowly moved till the anode current of the high frequency generator shows a
maximum in the meter. Now the initial reading of the micrometer screw is noted. If the micrometer is rotated
in the same direction, the current various between minimum and maximum.Micrometer screw is rotated in
the same direction until n
th
maximum in the micro ammeter is reached. The reading in the micrometer is
noted.
For n number of maximum anode current, the distance moved (d) is measured with the help of
micrometer. Hence
d = n?/2Therefore, ? = 2d/n
The frequency of the ultrasonic waves is noted as f (Hz)
The experiment is repeated for various n number of maximum and the readings are tabulated.
Knowing the meaning value of ?, the velocity of the ultrasonic waves is calculated.
FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
2


PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science and fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems and use this knowledge to acquire
higher education.
2. Core competence
To train the students in Engineering Physics so as to apply their knowledge and training to compare,
and to analyze various engineering industrial problems for finding solutions.
3. Breadth
To provide relevant training and experience to bridge the gap between theoretical learning and
practice that enables them to find solutions for the real time problems in industry and to design products.
4. Professionalism
To inculcate professional and effective communication skills, leadership qualities and team spirit for
the students to make them multi-faceted personalities and develop their ability to relate engineering issues
to broader social context.
5. Lifelong learning/ethics
To demonstrate and practice ethical and professional responsibilities in the industry and society by
and large, through commitment and lifelong learning needed for successful professional career.





3


PROGRAMME OUTCOMES (POs)

a) To demonstrate and apply knowledge of Mathematics, Science and Engineering fundamentals in
Engineering physics
b) To determine the Moment of Inertia of given disc and Rigidity modulus of the given wire using
Torsional Pendulum
c) To determine Young?s modulus of a given bar using Non-Uniform bending
d) To utilize laser source and grating to estimate the wave length, particle size of given powder and
Numerical Aperture & acceptance angle of given optical fiber
e) To find the Thermal conductivity of a bad conductor using Lee?s Disc method
f) To Measure the velocity of ultrasonic wave in a liquid and compressibility of the liquid usingultrasonic
Interferometer
g) To determine the wavelength of Hg source using grating and spectrometer
h) To find the thickness of a thin wire using Air- wedge method
i) To participate and succeed in competitive exams and visualize and work on laboratory and
multidisciplinary tasks











4


BS 8161 ? PHYSICSLABORATORY
(Common to all branches of B.E. / B.TechProgrammes)
SYLLABUS


To introduce different experiments to test basic understanding of physics concepts applied in optics, thermal
physics, properties of matter and liquids.

LIST OF EXPERIMENTS: PHYSICS LABORATORY(Any 5 Experiments)
1. Determination of Rigidity modulus ? Torsion pendulum
2. Determination of Young? s modulus by Non uniform bending method
3. (a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
4. Determination of thermal conductivity of a bad conductor ? Lee?s Disc method.
5. Determination of velocity of sound and compressibility of liquid ? Ultrasonic interferometer
6. Determination of wavelength of mercury spectrum ? spectrometer grating
7. Determination of band gap of a semiconductor
8. Determination of thickness of a thin wire ? Air wedge method




Completion of the course, the students will be able to: apply physics principles of optics and thermal physics
to evaluate engineering properties of materials.


COURSE OUTCOMES
COURSE OBJECTIVES
5

BS 8161 ? PHYSICS LABORATORY
CONTENTS

Sl.No. Name of the Experiment (any 5 experiments)
Page
No.
1.
Determination of Rigidity modulus ? Torsion pendulum
6
2.
Determination of Young ?s modulus by Non uniform bending method
12
3.
(a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
18
4.
Determination of thermal conductivity of a bad conductor ? Lee ?s Disc method.
28
5.
Determination of velocity of sound and compressibility of liquid ? Ultrasonic
interferometer
37
6.
Determination of wavelength of mercury spectrum ? spectrometer grating
42
7.
Determination of thickness of a thin wire ? Air wedge method
48
MEASURING INSTRUMENTS
M1 Screw gauge 54
M2 Vernier Calipers 58
M3 Travelling Microscope 62
M4 Spectrometer 66








6

TORSIONAL PENDULUM










7

Expt. No.1 TORSIONAL PENDULUM

AIM:
To determine the moment of inertia of the given disc and hence to determine the rigidity modulus of
the material of the given suspension wire by torsional oscillations
APPARATUS REQUIRED:
Torsional pendulum, two equal masses, stop clock, screw gauge and meter scale

FORMULA:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
where
m ?mass of the cylinder placed on the disc (kg)
To ?period of the pendulum for a length of l without mass (s)
T1?period of the pendulum for the same length when mass m is placed at a distance d 1
from the center of the suspension wire (s)
T2?period of the pendulum for the same length when mass m is placed at a distance d 2
from the center of the suspension wire (s)
a ? radius of the suspension wire (m)




8

1. To determine the time period of the disc:
Length of the wire (l)= --------
2
10
?
? m
Position of the equal
masses
Time for 10 oscillations Time period
(one oscillation)
s
Trial-1
s
Trial-2
s
Mean
s
Without any masses T0
With masses at
d1 = x10
-2
m
T1
With masses at
d2 = x10
-2
m
T2

2. To determine the radius of the wire:
Least count =0 .01 mm. Zero Error ZE = --------- divisions
Zero Correction ZC = ---------- mm

Sl.No.
Pitch Scale
Reading
PSR
3
10
?
? m
Head Scale
Coincidence
HSC
div
Observed reading
OR = PSR + (HSCXLC)
3
10
?
? m
Correct reading
CR = OR ? ZC
3
10
?
? m




Mean = ----------------
3
10
?
? m



9

PROCEDURE:
Torsional pendulum is suspended from vertical chuck. The length of the suspension wire is measured
between the vertical chuck and the chuck attached to the uniform circular disc (i). The circular disc is twisted
slightly without masses on the disc. Now it executes torsional oscillations. Care is taken to see that the disc
oscillates without wobbling. Time taken for 20 oscillations is noted with the help of a stop clock. Two trials are
taken. The average of these two trial readings is calculated from which the period of oscillations is found out
as T0.
Two identical cylindrical masses each of mass m are symmetrically placed on the disc on either side
of the wire at a distance d from the center of the disc. As before the disc is gently twisted. Time taken for 20
oscillations is noted from which the period of oscillation is calculated as T1.
The cylindrical masses are placed at a distance d2 from the center and the experiment is repeated.
The mean time period of oscillations is calculated T2.
The diameter of the specimen wire is measured accurately with the help of the screw gauge, at
various places on the wire. The average diameter and hence the radius of the wire is calculated as r.
Moment of inertia and the rigidity modulus are determined by the substituting the value of m, T 0, T1, T2,
T3, and l in the formula.










10

CALCULATION:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2

Mass of cylindrical mass, m = ----------- ? 10
-3
kg
Closest distance of the mass from the centre of the suspension wire, d1 = ------------ ? 10
-2
m
Farthest distance of the mass from the centre of suspension wire, d2= ------------? 10
-2
m
Period of oscillation without mass, To = ------------- s
Period of oscillation with mass at d1, T1= ------------ s
Period of oscillation with mass at d2, T2 = ------------- s

Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
= --------------- kg m
2
= --------------- kg m
2

Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
Moment of inertia, I = ------------------ kg m
2
Length of the wire, l = ------------------- ? 10
-2
m
Time of oscillation, To = ------------------ s
Radius of the wire, a = ------------------- ? 10
-3
m
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
= ----------------------
Rigidity modulus, n = ------------------- Nm
-2
11









RESULT:
(i)
The moment of inertia of the given circular disc, I = --------------- kg m
2
(ii)
The rigidity modulus of the material of the given wire, n = -------------- Nm
-2




1. State Hooke?s law.
2. Define ?Rigidity modulus
3. Define ?Moment of inertia
4. What is meant by torsional oscillation?
5. What is period of oscillation?
6. What is meant by twisting couple?
7. Define ? Shearing stress
8. Define ? Shearing strain
9. What is the unit of rigidity modulus?
10. What are the applications of torsional pendulum?


Viva ? voce
12


Young?s Modulus ? Non Uniform Bending
To determine depression (y):
L.C =.001cm M = ___________
3
10
?
? kg

Sl.No

Load


3
10
?
?
k
g
Microscope reading
Mean

2
10
?
? m
Depression
y for M kg

2
10
?
? m
Loading Unloading
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
1 W
2 W+50
3 W+100
4 W+150
5 W+200
6 W+250

Mean (y) = ----------
2
10
?
? m





13

Expt. No.2 YOUNG?S MODULUS BY NON ? UNIFORM BENDING
AIM:
To determine the young?s modulus of the material of the given bar, by non-uniform bending method
APPARATUS REQUIRED:
Travelling microscope, wooden bar, knife- edge, weights hanger, slotted weight, vernier calipers,
screw gauge and pin
FORMULA:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Where,
g ? acceleration due to gravity (9.8 ms
-2
)
l ? length of the bar between two knife edges (m)
b ? breadth of the bar (m)
d ? thickness of the bar (m)
y ? depressiont in the scale reading due to the change of mass M (m)
PROCEDURE:
The given wooden bar, for which young?s modulus is to be determined, is paced symmetrically on the
two knife edges. The distance between the knife edges is measured as the length of the bar (l). It is adjusted
to be, say, 60 cm. the weight hanger is suspended at the centre of the bar. A pin is held vertically at the
centre of the bar with the help of wax.
The given bar is brought to elastic mood by loading and unloading the bar with slotted weights in steps
of 50 g. This is repeated for two or three times. With the hanger as dead load W, the microscope is focused on
to the tip of the pin. The tangential screw of the microscope is adjusted so that the image of the tip of the pin
just touches the horizontal cross wire of the eyepiece. The main scale reading and the vernier scale
coincidence corresponding to this position are noted.
14

To find the breadth using vernier calipers, b:
Least count = ---------- cm Zero error = --------- div.
= ---------- ?10
-2
m Zero correction = ?ZE ?LC= --------- ?10
-2
m
Sl. No.

MSR
x 10
-2
m

VSC
div.
Observed reading
OR = MSR+(VSC ? LC)
x 10
-2
m
Correct Reading
CR = OR ? ZC
x 10
-2
m
1.

2.

3.


Mean, b = ------------------------?10
-2
m
To find the thickness using screw gauge, d:
Least count = ---------- mm Zero error = --------- div.
= ---------- ?10
-3
m Zero correction =ZE ?LC= --------- ?10
-3
m
Sl. No.

PSR
x 10
-3
m

HSC
div.
Observed reading
OR = PSR+ (HSC ? LC)
x 10
-3
m
Correct Reading
CR = OR ? ZC
x 10
-3
m
1.

2.

3.


Mean, d = ---------------------------?10
-3
m
15


The experiment is repeated by adding weights in steps of 50 g and every time the microscope is
adjusted for coincidence. The corresponding readings are noted. The experiment is repeated by unloading the
weights in steps of 50 g and the corresponding readings are tabulated. From this table, the shift in the scale
reading, say y, for a change of mass M is found out.
The breadth of the bar is measured at various points with the help of vernier calipers. Similarly the
thickness of the bar is measured by screw gauge. Substituting the values of M, y, l, d, b and g in the formula,
the young?s modulus of the material of the given bar is calculated.

















16

CALCULATION:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Acceleration due to gravity, g = 9.8 ms
-2
Length of the bar between two knife edges, l = ------------ ?10
-2
m
Breadth of the bar, b = ----------- ?10
-2
m
Thickness of the bar, d = ----------- ?10
-3
m
y = -----------?10
-2
m
E =
???? ?? 2
4?? ?? 3
?? Nm
-2

= ---------------
Young?s modulus, E = ----------- Nm
-2












17








RESULT:
Young?s modulus of the material of the given bar, E = ---------- Nm
-2


1. Define ? Young?s modulus
2. What is meant by Non-uniform bending?
3. Define ? Stress and strain
4. State Hooke?s law.
5. Define ? Neutral axis
6. What is the SI unit of young?s modulus?
7. Define ? Elastic limit
8. Define ? Elasticity
9. What are the factors affecting elasticity?
10. Define ? Elastic fatigue

Viva ? voce
18


To find the wavelength of the laser beam, ?:
Distance between the screen and the grating, D = ------------?10
-2
m
Number of lines per meter length of the grating, N = --------------- Lines per meter
Sl. No.
Order of diffraction,
(m)
Reading of the diffracted image
(?10
-2
m)
?? ?? = ?????? ?1
(
?? ?? ?? )
(deg.)
? =
?????? ?? ?? ????
m

Left side
(xi)
Right side
(xr)
Mean
(xm)










Mean, ? = ---------------- m


19

Expt. No.3(a) WAVELENGTH OF LASER LIGHT AND PARTICLE SIZE


AIM:
(i) To determine the wavelength of the given laser light.
(ii) To determine size of the given particle.
APPARATUS REQUIRED:
Diode laser, grating, screen, given micro particles, scale and screen.
FORMULAE:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
(ii) Grain size or diameter of the grain, 2d =
?????? ?? ?? m
Where
?? ?? ?angle of diffraction (deg.)
M ?order of diffraction (No unit)
N ?number of lines per metre length of the grating (m
-3
)
n ? order of diffraction (no unit)
? ? wavelength of laser light used (m)
D ? distance between the glass plate and the screen (m)
?? ?? - distance between the central bright spot and the nth fringe (m)
PROCEDURE:
TO FIND THE WAVELENGTH OF THE GIVEN LASER LIGHT:
The laser source, grating and screen are placed properly as shown in figure. The diode laser is kept
horizontally and switched on. Extreme care should be taken to avoid direct exposure of laser light on eyes.
20











21

The grating is held normal to the laser beam by adjusting the grating in such a way that the reflected
laser beam from the grating coincides with incident laser beam. Now the diffracted laser spots of various
orders can be seen on the screen, placed on the other side of the grating.

The distance of the different orders on either side of the central spot are measured as x randxi and are
tabulated.The mean value of xrandxiare calculated as xm for the m
th
order diffracted light. The distance
between the grating and the screen is measured as D. Hence, the angle of diffraction for the m
th
order,
?? ?? = ?????? ?1
(
?? ?? ?? )
The experiment is repeated for different orders and the readings are tabulated. From the table, ? for
each order is calculated. Substituting the value of ?, the corresponding order of diffraction and the number of
lines per meter length of the grating, the wavelength is calculated.

TO FIND THE SIZE OF THE GIVEN MICRO PARTICLE:

The lycopodium powder having fine micro particles of nearly same size is sprinkled on a glass plate.
This glass plate is kept between laser source and screen.
Now the particles present in the glass plate diffract laser beam from the source. By adjusting the
distance between the glass plate and the screen, a circular fringe pattern is obtained on the screen with
different orders of fingers. Now distance between the screen and the glass plate (D) is measured.
The distance of the first order and the second order fringe from the centre of spot are also measured.
Using the formula, the particle size is found out. The experiment is repeated for different D values.
22

To find the size of the particle:

CALCULATION:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
Number of lines per metre in the grating, N = ------------ lines per metre.
First order, m1; ?? 1
= ------------
Wavelength, ? =
?????? ?? 1
????
= ------------
Second order, m2; ?? 2
= ------------
Wavelength, ? =
?????? ?? 2
????
= ------------
Third order, m3; ?? 3
= ------------
Wavelength, ? =
?????? ?? 3
????
= ------------
Fourth order, m4; ?? 4
= ------------
Wavelength, ? =
?????? ?? 4
????
= -------------
Fifth order, m5; ?? 5
= ------------

Sl.No



Distance between
screen and glass
plate(D)
2
10
?
? m
Order of
diffraction
(n)
Distance between the
central bright spot and n
th

fringe (xn )
2
10
?
? m
Particle size
2
n
nD
d
x
?
?
m






23

Wavelength, ? =
?????? ?? 4
????
= ------------
Mean wavelength of the given laser light, ? = -------------- m
(ii) Grain size or diameter of the grain. 2d =
?????? ?? ??
Order of differaction, n = --------------
Wavelength of laser light used, ? = ------------- m
Distance between glass plate and the screen, D = ------------ m
Distance between central bright spot and the n
th
fringe,?? ?? = ------------ m
2d =
?????? ?? ??
=
= ------------ m








RESULT:
(i) Wavelength of the laser beam, ? = -------------- m
(ii) Average size of the particle = --------------- m

24


Optical fiber

To find numerical aperture, NA:

Sl. No.
Diameter of the circular patch
D(m)
Distance between the tip of the
fiber and the screen X (m)
NA =
?? (4?? 2
+?? 2
)
1
2





Mean NA =
Therefore, the acceptance angle, ? = Sin
-1
(NA) = -------------------
= -------------------


25

Expt. No.3(b) NUMERICAL APERTURE AND ACCEPTANCE ANGLE
AIM:
To measure the numerical aperture and the acceptance angle of the given fiber cable
APPARATUS REQUIRED:
Optical fiber cable with source, NA jig and in-line adaptor
FORMULA:
The numerical aperture, NA =
?? (4?? 2
+?? 2
)
1
2

Acceptance angle, ? = Sin
-1
(NA)
where,
D ? diameter of the circular patch (m)
X ? distance between the tip of the fiber and the screen (m)
PROCEDURE:
One end of the one metre fiber cable is connected to the laser light source and the other end
to the NA jig as shown in figure. The AC main is plugged in and the laser light is adjusted so that it appears at
the end of the fiber on the NA jig, the intensity knob is adjusted to get maximum intensity.
The white screen with the four concentric circles (10 mm, 20 mm, 30 mm and 40 mm diameter) is held
vertically at a suitable distance to make the red spot from the emitting fiber coincides with the 10 mm circle,
the diameter (D) of the spot is noted. The distance (X) of the screen from the fiber end is recorded.
The procedure is repeated for 20 mm, 30 mm, 40 mm diameter circles and the readings are tabulated.




26

















RESULT:
The numerical aperture, NA = ----------------
Acceptance angle, ? = ----------------




27




1. What is semiconductor diode laser?
2. What is meant by active material in laser?
3. What is meant by LASER?
4. What is stimulated emission?
5. What are the characteristics of laser radiation?
6. What is homo?junction laser?
7. What is hetero?junction laser?
8. What are the applications of semiconductor laser?
9. What are the conditions required for laser action?
10. Define ? Numerical aperture







Viva ? voce
28


Lee?s disc setup


29

Expt. No. 4 THERMAL CONDUCTIVITY OF A BAD CONDUCTOR
BY LEE?S DISC METHOD

AIM:
To determine the coefficient of thermal conductivity of a bad conductor
APPARATUS REQUIRED:
Lee?s disc apparatus, bad conductors, stop-clock, thermometers, screw gauge, vernier calipers and
steam boiler
FORMULA:
Thermal conductivity of a bad conductor,
? ?
? ? ? ?
1 1
2 1
2
2 2
2
? ?
? ?
?
?
?
?
?
?
?
?
?
? k Wm
h r r
h r d
dt
d
MS
K
? ? ?
?

M ? Mass of the metallic disc (Kg)
S ? Specific heat capacity of the metallic disc ( J Kg
-1
K
-1
)
? rate of cooling at steady temperature (
o
C/s)
d ? thickness of the bad conductor (m)
h ? thickness of the metallic disc (m)
r?radius of the metallic disc (m)
1
? ? steady temperature of the steam chamber (
o
C)
2
? ? steady temperature of the Metallic disc (
o
C)

PROCEDURE:
The thickness of the bad conductor say card board and thickness of the metallic disc are determined
using a screw gauge. The radius of the metallic disc is found using a vernier caliper. The mass of a metallic
disc is also found using a common balance. The readings are tabulated.

30

To find the radius of the metallic disc (r) using Vernier Calipers
Least count = 0.01cm Zero error = ? ???div
Zero correction = ? ???cm
= --------- ?10
-2
m
Sl.No.
MSR
(x10
-2
m)
VSC
(div.)
OR = MSR +(VSC x LC)
(x10
-2
m)
CR = OR ? ZC
(x10
-2
m)
1
2
3
4

Mean radius, r = --------------------------------- x10
-2
m
To find the thickness of the bad conductor (d) using Screw gauge
Least count = 0.01mm Zero error = ? ???div
Zero correction = ? ???mm
Sl.No.
PSR
(x10
-3
m)
HSC
(div.)
OR = PSR + (HSC x LC)
(x10
-3
m)
CR = OR ? ZC
(x10
-3
m)
1.
2.
3.
4.

Mean, d = -------------------------------- x10
-3
m
31

The whole Lee?s disc apparatus is suspended from a stand as shown in the figure. The given bad
conductor is placed in between the metallic disc and the steam chamber. Two thermometers T1 and T2 are
inserted into the respective holes.
Steam from the steam boiler is passed into the steam chamber until the temperature of the steam
chamber and the metallic disc are steady. The Steady temperature (?1) of the steam chamber and (?2) of the
metallic disc recorded by the thermometers are noted.
Now the bad conductor is removed and the steam chamber is placed in direct contact with the metallic
disc. The temperature of the disc rapidly rises. When the temperature of the disc rises about 10
o
Cabove
?2
o
C, the steam chamber is carefully removed after cutting of the steam supply.
When the temperature of the disc reaches 10
o
C above the steady temperature of the disc i.e. (?2+
10)
o
C , stop clock is started. Time for every one degree celsius fall of temperature is noted until the metallic
disc attains a temperature (?2 - 10)
o
C.
A graph is drawn taking time along the x-axis and temperature along the y-axis. The cooling curve is
obtained .To obtain the rate of the cooling (
????
????
)
?? 2
from this graph, a triangle is drawn by taking 1
o
C above
and 1
o
Cbelow the steady temperature ?2. Then the slope AB / BC gives the rate of cooling at(
????
????
)
?? 2
. From
these readings and using the given formula thermal conductivity of the given bad conductor is calculated.










32

To find the thickness of the metallic disc (h) using screw gauge
Least count = 0.01mm Zero error = ? ???div
Zero correction = ? ???mm
Sl.No.
PSR
(x10
-3
m)
HSC
(div.)
TR = PSR + (HSC x LC)
(x10
-3
m)
Corrected reading
CR = TR ? ZC
(x10
-3
m)
1
2
3
4
5

Mean, h = ------------------------------ x10
-3
m
To determine the rate of cooling of metallic disc:
Time
s
Temperature
o
C
Time
s
Temperature
o
C







33

CALCULATION:
Mass of the disc, m= ---------- x10
-3
kg
Specific heat capacity of the disc,c = 385 J kg
-1
K
-1
Rate of cooling at ?2,
????
????
= -------------- deg s
-1
Radius of the disc, r = ---------- x10
-2
m
Height of the disc, h = ---------- x10
-2
m
Thickness of the bad conductor, d = ---------- x10
-3 m
Temperature of steam, ?1 = ---------
o
C
Steady temperature of the disc, ?2 = -------------
o
C
Thermal conductivity,
? ?
? ? ? ?
1 1
2 1
2
2 2
2
? ?
? ?
?
?
?
?
?
?
?
?
?
? k Wm
h r r
h r d
dt
d
MS
K
? ? ?
?


= --------------------

= -------------------- Wm
-1
K
-1








34
















RESULT:
The thermal conductivity of the given bad conductor by Lee?s disc method, K = -------------- Wm
-1
K
-1







35





1. What is meant by thermal conductivity?
2. What is meant by Rate of cooling?
3. Does the value of thermal conductivity depend on the dimension of the specimen?
4. Is there any reason to take the specimen in the form of a disc?
5. Can this method be used for good conductors?
6. What is lee's disc method?
7. What are the differences between good conductor and bad conductor?
8. What are the methods used to determine thermal conductivity of bad conductor?
9. What is meant by steady temperature?
10. What is meant by specific heat capacity?

Viva ? voce
36




37


Exp. No. 5 ULTRASONIC INTERFEROMETER

AIM:
To determine the velocity of the ultrasonic waves in a given liquid and to find the compressibility of
the liquid using ultrasonic interferometer
APPARATUS REQUIRED:
Ultrasonic interferometer (high frequency) generator, measuring cell, the experimental liquid
and coaxial cables
FORMULA:
1) Velocity of the ultrasonic waves v = f ? ms
-1
where,
f ?frequency of the ultrasonic waves (Hz)
? ? wavelength of the ultrasonic waves in the liquid (m)

2) Compressibility of the liquid ? =
1
?? 2
?? m
2
N
-1
where
? ? density of the given liquid (kg m
-3
)
v? velocity of the ultrasonic waves with in the liquid (m s
-1
)
DESCRIPTION:
The interferometer consists of (i) high frequency generator and (ii) measuring cell. The high
frequency generator is used to excite the quartz plate fixed at the bottom of the measuring cell.
The exited quartz plate generates ultrasonic waves in the experimental liquid contained in the cell. A micro
ammeter is provided to observe the change in the current.
Two control knobs are also provided in the generator for the purpose of sensitivity regulation and also
adjustment. The measuring cell is a double walled cell to maintain constant temperature during

38


To find the wavelength of the ultrasonic waves in the liquid:

Order of
maximum current

Micrometer reading
Distance for n
maximum current, d
(x10
-3
m)
Wavelength
?=2d/n
(x10
-3
m)
PSR
(x10
-3
m)
HSR
(div)
TR
(x10
-3
m)

x
x+n
x+2n
x+3n



Wavelength, ? = ------------------ x10
-3
m
Frequency of ultrasonic waves = 2 MHz

CALCULATION:
1) The Velocity of the ultrasonic waves, v = f?
= ---------- m s
-1
The density of the given liquid ? = ---------- kg m
-3
2) Adiabatic compressibility of the liquid, ? =
1
?? 2
??
= -----------
Adiabatic compressibility of the liquid, ? = --------------


39

experiment.A fine micrometer arrangement is fixed at the top of the interferometer, enables the reflector
pates to move upward or downward through a known distance.
PRINCIPLE:
The velocity of the ultrasonic waves is determined using the interferometer. The principle used in the
measurement of velocity is based on the accurate determination of the wave length (?) of ultrasonic waves
in the liquid. The ultrasonic waves are reflected back by a removable metallic plate parallel to the crystal
.These two ultrasonic waves superimpose producing stationary wave pattern within the medium.

If the separation between these two plates is exactly an integral multiple of ?/2 of the ultrasonic
waves, acoustic resonance is produced in the standing waves.

This acoustic resonance gives rise to an electrical reaction on the generator and the anode current of the
generator becomes maximum.
PROCEDURE:
The measuring cell is connected to the output terminal of the high frequency generator through a
shielded cable. The cell is filled with an experimental liquid before switching on the generator. The
ultrasonic waves move normally from the quartz crystal till they are reflected back from the movable plate
and the standing waves are formed in the liquid in between the reflector plate and the quartz crystal.
The micrometer is slowly moved till the anode current of the high frequency generator shows a
maximum in the meter. Now the initial reading of the micrometer screw is noted. If the micrometer is rotated
in the same direction, the current various between minimum and maximum.Micrometer screw is rotated in
the same direction until n
th
maximum in the micro ammeter is reached. The reading in the micrometer is
noted.
For n number of maximum anode current, the distance moved (d) is measured with the help of
micrometer. Hence
d = n?/2Therefore, ? = 2d/n
The frequency of the ultrasonic waves is noted as f (Hz)
The experiment is repeated for various n number of maximum and the readings are tabulated.
Knowing the meaning value of ?, the velocity of the ultrasonic waves is calculated.
40

If the distance is now increased or decreased and the variation is exactly one half wavelengths
(?/2) or multiple of it, anode current becomes maximum. From the knowledge of wave length (?) the velocity
v can be obtained using the following relation.
v = f ?
By substituting the value of the density of the given liquid and the velocity of the ultrasonic waves in
the given liquid, the adiabatic compressibility of the given liquid is calculated.





RESULT:
i) Wave length of the ultrasonic waves in the liquid = ---------- m
ii) Velocity of the ultrasonic waves in the liquid = --------- m s-
1
iii) Compressibility of the given liquid = --------- N
-1
m
2








FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
2


PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science and fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems and use this knowledge to acquire
higher education.
2. Core competence
To train the students in Engineering Physics so as to apply their knowledge and training to compare,
and to analyze various engineering industrial problems for finding solutions.
3. Breadth
To provide relevant training and experience to bridge the gap between theoretical learning and
practice that enables them to find solutions for the real time problems in industry and to design products.
4. Professionalism
To inculcate professional and effective communication skills, leadership qualities and team spirit for
the students to make them multi-faceted personalities and develop their ability to relate engineering issues
to broader social context.
5. Lifelong learning/ethics
To demonstrate and practice ethical and professional responsibilities in the industry and society by
and large, through commitment and lifelong learning needed for successful professional career.





3


PROGRAMME OUTCOMES (POs)

a) To demonstrate and apply knowledge of Mathematics, Science and Engineering fundamentals in
Engineering physics
b) To determine the Moment of Inertia of given disc and Rigidity modulus of the given wire using
Torsional Pendulum
c) To determine Young?s modulus of a given bar using Non-Uniform bending
d) To utilize laser source and grating to estimate the wave length, particle size of given powder and
Numerical Aperture & acceptance angle of given optical fiber
e) To find the Thermal conductivity of a bad conductor using Lee?s Disc method
f) To Measure the velocity of ultrasonic wave in a liquid and compressibility of the liquid usingultrasonic
Interferometer
g) To determine the wavelength of Hg source using grating and spectrometer
h) To find the thickness of a thin wire using Air- wedge method
i) To participate and succeed in competitive exams and visualize and work on laboratory and
multidisciplinary tasks











4


BS 8161 ? PHYSICSLABORATORY
(Common to all branches of B.E. / B.TechProgrammes)
SYLLABUS


To introduce different experiments to test basic understanding of physics concepts applied in optics, thermal
physics, properties of matter and liquids.

LIST OF EXPERIMENTS: PHYSICS LABORATORY(Any 5 Experiments)
1. Determination of Rigidity modulus ? Torsion pendulum
2. Determination of Young? s modulus by Non uniform bending method
3. (a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
4. Determination of thermal conductivity of a bad conductor ? Lee?s Disc method.
5. Determination of velocity of sound and compressibility of liquid ? Ultrasonic interferometer
6. Determination of wavelength of mercury spectrum ? spectrometer grating
7. Determination of band gap of a semiconductor
8. Determination of thickness of a thin wire ? Air wedge method




Completion of the course, the students will be able to: apply physics principles of optics and thermal physics
to evaluate engineering properties of materials.


COURSE OUTCOMES
COURSE OBJECTIVES
5

BS 8161 ? PHYSICS LABORATORY
CONTENTS

Sl.No. Name of the Experiment (any 5 experiments)
Page
No.
1.
Determination of Rigidity modulus ? Torsion pendulum
6
2.
Determination of Young ?s modulus by Non uniform bending method
12
3.
(a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
18
4.
Determination of thermal conductivity of a bad conductor ? Lee ?s Disc method.
28
5.
Determination of velocity of sound and compressibility of liquid ? Ultrasonic
interferometer
37
6.
Determination of wavelength of mercury spectrum ? spectrometer grating
42
7.
Determination of thickness of a thin wire ? Air wedge method
48
MEASURING INSTRUMENTS
M1 Screw gauge 54
M2 Vernier Calipers 58
M3 Travelling Microscope 62
M4 Spectrometer 66








6

TORSIONAL PENDULUM










7

Expt. No.1 TORSIONAL PENDULUM

AIM:
To determine the moment of inertia of the given disc and hence to determine the rigidity modulus of
the material of the given suspension wire by torsional oscillations
APPARATUS REQUIRED:
Torsional pendulum, two equal masses, stop clock, screw gauge and meter scale

FORMULA:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
where
m ?mass of the cylinder placed on the disc (kg)
To ?period of the pendulum for a length of l without mass (s)
T1?period of the pendulum for the same length when mass m is placed at a distance d 1
from the center of the suspension wire (s)
T2?period of the pendulum for the same length when mass m is placed at a distance d 2
from the center of the suspension wire (s)
a ? radius of the suspension wire (m)




8

1. To determine the time period of the disc:
Length of the wire (l)= --------
2
10
?
? m
Position of the equal
masses
Time for 10 oscillations Time period
(one oscillation)
s
Trial-1
s
Trial-2
s
Mean
s
Without any masses T0
With masses at
d1 = x10
-2
m
T1
With masses at
d2 = x10
-2
m
T2

2. To determine the radius of the wire:
Least count =0 .01 mm. Zero Error ZE = --------- divisions
Zero Correction ZC = ---------- mm

Sl.No.
Pitch Scale
Reading
PSR
3
10
?
? m
Head Scale
Coincidence
HSC
div
Observed reading
OR = PSR + (HSCXLC)
3
10
?
? m
Correct reading
CR = OR ? ZC
3
10
?
? m




Mean = ----------------
3
10
?
? m



9

PROCEDURE:
Torsional pendulum is suspended from vertical chuck. The length of the suspension wire is measured
between the vertical chuck and the chuck attached to the uniform circular disc (i). The circular disc is twisted
slightly without masses on the disc. Now it executes torsional oscillations. Care is taken to see that the disc
oscillates without wobbling. Time taken for 20 oscillations is noted with the help of a stop clock. Two trials are
taken. The average of these two trial readings is calculated from which the period of oscillations is found out
as T0.
Two identical cylindrical masses each of mass m are symmetrically placed on the disc on either side
of the wire at a distance d from the center of the disc. As before the disc is gently twisted. Time taken for 20
oscillations is noted from which the period of oscillation is calculated as T1.
The cylindrical masses are placed at a distance d2 from the center and the experiment is repeated.
The mean time period of oscillations is calculated T2.
The diameter of the specimen wire is measured accurately with the help of the screw gauge, at
various places on the wire. The average diameter and hence the radius of the wire is calculated as r.
Moment of inertia and the rigidity modulus are determined by the substituting the value of m, T 0, T1, T2,
T3, and l in the formula.










10

CALCULATION:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2

Mass of cylindrical mass, m = ----------- ? 10
-3
kg
Closest distance of the mass from the centre of the suspension wire, d1 = ------------ ? 10
-2
m
Farthest distance of the mass from the centre of suspension wire, d2= ------------? 10
-2
m
Period of oscillation without mass, To = ------------- s
Period of oscillation with mass at d1, T1= ------------ s
Period of oscillation with mass at d2, T2 = ------------- s

Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
= --------------- kg m
2
= --------------- kg m
2

Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
Moment of inertia, I = ------------------ kg m
2
Length of the wire, l = ------------------- ? 10
-2
m
Time of oscillation, To = ------------------ s
Radius of the wire, a = ------------------- ? 10
-3
m
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
= ----------------------
Rigidity modulus, n = ------------------- Nm
-2
11









RESULT:
(i)
The moment of inertia of the given circular disc, I = --------------- kg m
2
(ii)
The rigidity modulus of the material of the given wire, n = -------------- Nm
-2




1. State Hooke?s law.
2. Define ?Rigidity modulus
3. Define ?Moment of inertia
4. What is meant by torsional oscillation?
5. What is period of oscillation?
6. What is meant by twisting couple?
7. Define ? Shearing stress
8. Define ? Shearing strain
9. What is the unit of rigidity modulus?
10. What are the applications of torsional pendulum?


Viva ? voce
12


Young?s Modulus ? Non Uniform Bending
To determine depression (y):
L.C =.001cm M = ___________
3
10
?
? kg

Sl.No

Load


3
10
?
?
k
g
Microscope reading
Mean

2
10
?
? m
Depression
y for M kg

2
10
?
? m
Loading Unloading
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
1 W
2 W+50
3 W+100
4 W+150
5 W+200
6 W+250

Mean (y) = ----------
2
10
?
? m





13

Expt. No.2 YOUNG?S MODULUS BY NON ? UNIFORM BENDING
AIM:
To determine the young?s modulus of the material of the given bar, by non-uniform bending method
APPARATUS REQUIRED:
Travelling microscope, wooden bar, knife- edge, weights hanger, slotted weight, vernier calipers,
screw gauge and pin
FORMULA:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Where,
g ? acceleration due to gravity (9.8 ms
-2
)
l ? length of the bar between two knife edges (m)
b ? breadth of the bar (m)
d ? thickness of the bar (m)
y ? depressiont in the scale reading due to the change of mass M (m)
PROCEDURE:
The given wooden bar, for which young?s modulus is to be determined, is paced symmetrically on the
two knife edges. The distance between the knife edges is measured as the length of the bar (l). It is adjusted
to be, say, 60 cm. the weight hanger is suspended at the centre of the bar. A pin is held vertically at the
centre of the bar with the help of wax.
The given bar is brought to elastic mood by loading and unloading the bar with slotted weights in steps
of 50 g. This is repeated for two or three times. With the hanger as dead load W, the microscope is focused on
to the tip of the pin. The tangential screw of the microscope is adjusted so that the image of the tip of the pin
just touches the horizontal cross wire of the eyepiece. The main scale reading and the vernier scale
coincidence corresponding to this position are noted.
14

To find the breadth using vernier calipers, b:
Least count = ---------- cm Zero error = --------- div.
= ---------- ?10
-2
m Zero correction = ?ZE ?LC= --------- ?10
-2
m
Sl. No.

MSR
x 10
-2
m

VSC
div.
Observed reading
OR = MSR+(VSC ? LC)
x 10
-2
m
Correct Reading
CR = OR ? ZC
x 10
-2
m
1.

2.

3.


Mean, b = ------------------------?10
-2
m
To find the thickness using screw gauge, d:
Least count = ---------- mm Zero error = --------- div.
= ---------- ?10
-3
m Zero correction =ZE ?LC= --------- ?10
-3
m
Sl. No.

PSR
x 10
-3
m

HSC
div.
Observed reading
OR = PSR+ (HSC ? LC)
x 10
-3
m
Correct Reading
CR = OR ? ZC
x 10
-3
m
1.

2.

3.


Mean, d = ---------------------------?10
-3
m
15


The experiment is repeated by adding weights in steps of 50 g and every time the microscope is
adjusted for coincidence. The corresponding readings are noted. The experiment is repeated by unloading the
weights in steps of 50 g and the corresponding readings are tabulated. From this table, the shift in the scale
reading, say y, for a change of mass M is found out.
The breadth of the bar is measured at various points with the help of vernier calipers. Similarly the
thickness of the bar is measured by screw gauge. Substituting the values of M, y, l, d, b and g in the formula,
the young?s modulus of the material of the given bar is calculated.

















16

CALCULATION:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Acceleration due to gravity, g = 9.8 ms
-2
Length of the bar between two knife edges, l = ------------ ?10
-2
m
Breadth of the bar, b = ----------- ?10
-2
m
Thickness of the bar, d = ----------- ?10
-3
m
y = -----------?10
-2
m
E =
???? ?? 2
4?? ?? 3
?? Nm
-2

= ---------------
Young?s modulus, E = ----------- Nm
-2












17








RESULT:
Young?s modulus of the material of the given bar, E = ---------- Nm
-2


1. Define ? Young?s modulus
2. What is meant by Non-uniform bending?
3. Define ? Stress and strain
4. State Hooke?s law.
5. Define ? Neutral axis
6. What is the SI unit of young?s modulus?
7. Define ? Elastic limit
8. Define ? Elasticity
9. What are the factors affecting elasticity?
10. Define ? Elastic fatigue

Viva ? voce
18


To find the wavelength of the laser beam, ?:
Distance between the screen and the grating, D = ------------?10
-2
m
Number of lines per meter length of the grating, N = --------------- Lines per meter
Sl. No.
Order of diffraction,
(m)
Reading of the diffracted image
(?10
-2
m)
?? ?? = ?????? ?1
(
?? ?? ?? )
(deg.)
? =
?????? ?? ?? ????
m

Left side
(xi)
Right side
(xr)
Mean
(xm)










Mean, ? = ---------------- m


19

Expt. No.3(a) WAVELENGTH OF LASER LIGHT AND PARTICLE SIZE


AIM:
(i) To determine the wavelength of the given laser light.
(ii) To determine size of the given particle.
APPARATUS REQUIRED:
Diode laser, grating, screen, given micro particles, scale and screen.
FORMULAE:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
(ii) Grain size or diameter of the grain, 2d =
?????? ?? ?? m
Where
?? ?? ?angle of diffraction (deg.)
M ?order of diffraction (No unit)
N ?number of lines per metre length of the grating (m
-3
)
n ? order of diffraction (no unit)
? ? wavelength of laser light used (m)
D ? distance between the glass plate and the screen (m)
?? ?? - distance between the central bright spot and the nth fringe (m)
PROCEDURE:
TO FIND THE WAVELENGTH OF THE GIVEN LASER LIGHT:
The laser source, grating and screen are placed properly as shown in figure. The diode laser is kept
horizontally and switched on. Extreme care should be taken to avoid direct exposure of laser light on eyes.
20











21

The grating is held normal to the laser beam by adjusting the grating in such a way that the reflected
laser beam from the grating coincides with incident laser beam. Now the diffracted laser spots of various
orders can be seen on the screen, placed on the other side of the grating.

The distance of the different orders on either side of the central spot are measured as x randxi and are
tabulated.The mean value of xrandxiare calculated as xm for the m
th
order diffracted light. The distance
between the grating and the screen is measured as D. Hence, the angle of diffraction for the m
th
order,
?? ?? = ?????? ?1
(
?? ?? ?? )
The experiment is repeated for different orders and the readings are tabulated. From the table, ? for
each order is calculated. Substituting the value of ?, the corresponding order of diffraction and the number of
lines per meter length of the grating, the wavelength is calculated.

TO FIND THE SIZE OF THE GIVEN MICRO PARTICLE:

The lycopodium powder having fine micro particles of nearly same size is sprinkled on a glass plate.
This glass plate is kept between laser source and screen.
Now the particles present in the glass plate diffract laser beam from the source. By adjusting the
distance between the glass plate and the screen, a circular fringe pattern is obtained on the screen with
different orders of fingers. Now distance between the screen and the glass plate (D) is measured.
The distance of the first order and the second order fringe from the centre of spot are also measured.
Using the formula, the particle size is found out. The experiment is repeated for different D values.
22

To find the size of the particle:

CALCULATION:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
Number of lines per metre in the grating, N = ------------ lines per metre.
First order, m1; ?? 1
= ------------
Wavelength, ? =
?????? ?? 1
????
= ------------
Second order, m2; ?? 2
= ------------
Wavelength, ? =
?????? ?? 2
????
= ------------
Third order, m3; ?? 3
= ------------
Wavelength, ? =
?????? ?? 3
????
= ------------
Fourth order, m4; ?? 4
= ------------
Wavelength, ? =
?????? ?? 4
????
= -------------
Fifth order, m5; ?? 5
= ------------

Sl.No



Distance between
screen and glass
plate(D)
2
10
?
? m
Order of
diffraction
(n)
Distance between the
central bright spot and n
th

fringe (xn )
2
10
?
? m
Particle size
2
n
nD
d
x
?
?
m






23

Wavelength, ? =
?????? ?? 4
????
= ------------
Mean wavelength of the given laser light, ? = -------------- m
(ii) Grain size or diameter of the grain. 2d =
?????? ?? ??
Order of differaction, n = --------------
Wavelength of laser light used, ? = ------------- m
Distance between glass plate and the screen, D = ------------ m
Distance between central bright spot and the n
th
fringe,?? ?? = ------------ m
2d =
?????? ?? ??
=
= ------------ m








RESULT:
(i) Wavelength of the laser beam, ? = -------------- m
(ii) Average size of the particle = --------------- m

24


Optical fiber

To find numerical aperture, NA:

Sl. No.
Diameter of the circular patch
D(m)
Distance between the tip of the
fiber and the screen X (m)
NA =
?? (4?? 2
+?? 2
)
1
2





Mean NA =
Therefore, the acceptance angle, ? = Sin
-1
(NA) = -------------------
= -------------------


25

Expt. No.3(b) NUMERICAL APERTURE AND ACCEPTANCE ANGLE
AIM:
To measure the numerical aperture and the acceptance angle of the given fiber cable
APPARATUS REQUIRED:
Optical fiber cable with source, NA jig and in-line adaptor
FORMULA:
The numerical aperture, NA =
?? (4?? 2
+?? 2
)
1
2

Acceptance angle, ? = Sin
-1
(NA)
where,
D ? diameter of the circular patch (m)
X ? distance between the tip of the fiber and the screen (m)
PROCEDURE:
One end of the one metre fiber cable is connected to the laser light source and the other end
to the NA jig as shown in figure. The AC main is plugged in and the laser light is adjusted so that it appears at
the end of the fiber on the NA jig, the intensity knob is adjusted to get maximum intensity.
The white screen with the four concentric circles (10 mm, 20 mm, 30 mm and 40 mm diameter) is held
vertically at a suitable distance to make the red spot from the emitting fiber coincides with the 10 mm circle,
the diameter (D) of the spot is noted. The distance (X) of the screen from the fiber end is recorded.
The procedure is repeated for 20 mm, 30 mm, 40 mm diameter circles and the readings are tabulated.




26

















RESULT:
The numerical aperture, NA = ----------------
Acceptance angle, ? = ----------------




27




1. What is semiconductor diode laser?
2. What is meant by active material in laser?
3. What is meant by LASER?
4. What is stimulated emission?
5. What are the characteristics of laser radiation?
6. What is homo?junction laser?
7. What is hetero?junction laser?
8. What are the applications of semiconductor laser?
9. What are the conditions required for laser action?
10. Define ? Numerical aperture







Viva ? voce
28


Lee?s disc setup


29

Expt. No. 4 THERMAL CONDUCTIVITY OF A BAD CONDUCTOR
BY LEE?S DISC METHOD

AIM:
To determine the coefficient of thermal conductivity of a bad conductor
APPARATUS REQUIRED:
Lee?s disc apparatus, bad conductors, stop-clock, thermometers, screw gauge, vernier calipers and
steam boiler
FORMULA:
Thermal conductivity of a bad conductor,
? ?
? ? ? ?
1 1
2 1
2
2 2
2
? ?
? ?
?
?
?
?
?
?
?
?
?
? k Wm
h r r
h r d
dt
d
MS
K
? ? ?
?

M ? Mass of the metallic disc (Kg)
S ? Specific heat capacity of the metallic disc ( J Kg
-1
K
-1
)
? rate of cooling at steady temperature (
o
C/s)
d ? thickness of the bad conductor (m)
h ? thickness of the metallic disc (m)
r?radius of the metallic disc (m)
1
? ? steady temperature of the steam chamber (
o
C)
2
? ? steady temperature of the Metallic disc (
o
C)

PROCEDURE:
The thickness of the bad conductor say card board and thickness of the metallic disc are determined
using a screw gauge. The radius of the metallic disc is found using a vernier caliper. The mass of a metallic
disc is also found using a common balance. The readings are tabulated.

30

To find the radius of the metallic disc (r) using Vernier Calipers
Least count = 0.01cm Zero error = ? ???div
Zero correction = ? ???cm
= --------- ?10
-2
m
Sl.No.
MSR
(x10
-2
m)
VSC
(div.)
OR = MSR +(VSC x LC)
(x10
-2
m)
CR = OR ? ZC
(x10
-2
m)
1
2
3
4

Mean radius, r = --------------------------------- x10
-2
m
To find the thickness of the bad conductor (d) using Screw gauge
Least count = 0.01mm Zero error = ? ???div
Zero correction = ? ???mm
Sl.No.
PSR
(x10
-3
m)
HSC
(div.)
OR = PSR + (HSC x LC)
(x10
-3
m)
CR = OR ? ZC
(x10
-3
m)
1.
2.
3.
4.

Mean, d = -------------------------------- x10
-3
m
31

The whole Lee?s disc apparatus is suspended from a stand as shown in the figure. The given bad
conductor is placed in between the metallic disc and the steam chamber. Two thermometers T1 and T2 are
inserted into the respective holes.
Steam from the steam boiler is passed into the steam chamber until the temperature of the steam
chamber and the metallic disc are steady. The Steady temperature (?1) of the steam chamber and (?2) of the
metallic disc recorded by the thermometers are noted.
Now the bad conductor is removed and the steam chamber is placed in direct contact with the metallic
disc. The temperature of the disc rapidly rises. When the temperature of the disc rises about 10
o
Cabove
?2
o
C, the steam chamber is carefully removed after cutting of the steam supply.
When the temperature of the disc reaches 10
o
C above the steady temperature of the disc i.e. (?2+
10)
o
C , stop clock is started. Time for every one degree celsius fall of temperature is noted until the metallic
disc attains a temperature (?2 - 10)
o
C.
A graph is drawn taking time along the x-axis and temperature along the y-axis. The cooling curve is
obtained .To obtain the rate of the cooling (
????
????
)
?? 2
from this graph, a triangle is drawn by taking 1
o
C above
and 1
o
Cbelow the steady temperature ?2. Then the slope AB / BC gives the rate of cooling at(
????
????
)
?? 2
. From
these readings and using the given formula thermal conductivity of the given bad conductor is calculated.










32

To find the thickness of the metallic disc (h) using screw gauge
Least count = 0.01mm Zero error = ? ???div
Zero correction = ? ???mm
Sl.No.
PSR
(x10
-3
m)
HSC
(div.)
TR = PSR + (HSC x LC)
(x10
-3
m)
Corrected reading
CR = TR ? ZC
(x10
-3
m)
1
2
3
4
5

Mean, h = ------------------------------ x10
-3
m
To determine the rate of cooling of metallic disc:
Time
s
Temperature
o
C
Time
s
Temperature
o
C







33

CALCULATION:
Mass of the disc, m= ---------- x10
-3
kg
Specific heat capacity of the disc,c = 385 J kg
-1
K
-1
Rate of cooling at ?2,
????
????
= -------------- deg s
-1
Radius of the disc, r = ---------- x10
-2
m
Height of the disc, h = ---------- x10
-2
m
Thickness of the bad conductor, d = ---------- x10
-3 m
Temperature of steam, ?1 = ---------
o
C
Steady temperature of the disc, ?2 = -------------
o
C
Thermal conductivity,
? ?
? ? ? ?
1 1
2 1
2
2 2
2
? ?
? ?
?
?
?
?
?
?
?
?
?
? k Wm
h r r
h r d
dt
d
MS
K
? ? ?
?


= --------------------

= -------------------- Wm
-1
K
-1








34
















RESULT:
The thermal conductivity of the given bad conductor by Lee?s disc method, K = -------------- Wm
-1
K
-1







35





1. What is meant by thermal conductivity?
2. What is meant by Rate of cooling?
3. Does the value of thermal conductivity depend on the dimension of the specimen?
4. Is there any reason to take the specimen in the form of a disc?
5. Can this method be used for good conductors?
6. What is lee's disc method?
7. What are the differences between good conductor and bad conductor?
8. What are the methods used to determine thermal conductivity of bad conductor?
9. What is meant by steady temperature?
10. What is meant by specific heat capacity?

Viva ? voce
36




37


Exp. No. 5 ULTRASONIC INTERFEROMETER

AIM:
To determine the velocity of the ultrasonic waves in a given liquid and to find the compressibility of
the liquid using ultrasonic interferometer
APPARATUS REQUIRED:
Ultrasonic interferometer (high frequency) generator, measuring cell, the experimental liquid
and coaxial cables
FORMULA:
1) Velocity of the ultrasonic waves v = f ? ms
-1
where,
f ?frequency of the ultrasonic waves (Hz)
? ? wavelength of the ultrasonic waves in the liquid (m)

2) Compressibility of the liquid ? =
1
?? 2
?? m
2
N
-1
where
? ? density of the given liquid (kg m
-3
)
v? velocity of the ultrasonic waves with in the liquid (m s
-1
)
DESCRIPTION:
The interferometer consists of (i) high frequency generator and (ii) measuring cell. The high
frequency generator is used to excite the quartz plate fixed at the bottom of the measuring cell.
The exited quartz plate generates ultrasonic waves in the experimental liquid contained in the cell. A micro
ammeter is provided to observe the change in the current.
Two control knobs are also provided in the generator for the purpose of sensitivity regulation and also
adjustment. The measuring cell is a double walled cell to maintain constant temperature during

38


To find the wavelength of the ultrasonic waves in the liquid:

Order of
maximum current

Micrometer reading
Distance for n
maximum current, d
(x10
-3
m)
Wavelength
?=2d/n
(x10
-3
m)
PSR
(x10
-3
m)
HSR
(div)
TR
(x10
-3
m)

x
x+n
x+2n
x+3n



Wavelength, ? = ------------------ x10
-3
m
Frequency of ultrasonic waves = 2 MHz

CALCULATION:
1) The Velocity of the ultrasonic waves, v = f?
= ---------- m s
-1
The density of the given liquid ? = ---------- kg m
-3
2) Adiabatic compressibility of the liquid, ? =
1
?? 2
??
= -----------
Adiabatic compressibility of the liquid, ? = --------------


39

experiment.A fine micrometer arrangement is fixed at the top of the interferometer, enables the reflector
pates to move upward or downward through a known distance.
PRINCIPLE:
The velocity of the ultrasonic waves is determined using the interferometer. The principle used in the
measurement of velocity is based on the accurate determination of the wave length (?) of ultrasonic waves
in the liquid. The ultrasonic waves are reflected back by a removable metallic plate parallel to the crystal
.These two ultrasonic waves superimpose producing stationary wave pattern within the medium.

If the separation between these two plates is exactly an integral multiple of ?/2 of the ultrasonic
waves, acoustic resonance is produced in the standing waves.

This acoustic resonance gives rise to an electrical reaction on the generator and the anode current of the
generator becomes maximum.
PROCEDURE:
The measuring cell is connected to the output terminal of the high frequency generator through a
shielded cable. The cell is filled with an experimental liquid before switching on the generator. The
ultrasonic waves move normally from the quartz crystal till they are reflected back from the movable plate
and the standing waves are formed in the liquid in between the reflector plate and the quartz crystal.
The micrometer is slowly moved till the anode current of the high frequency generator shows a
maximum in the meter. Now the initial reading of the micrometer screw is noted. If the micrometer is rotated
in the same direction, the current various between minimum and maximum.Micrometer screw is rotated in
the same direction until n
th
maximum in the micro ammeter is reached. The reading in the micrometer is
noted.
For n number of maximum anode current, the distance moved (d) is measured with the help of
micrometer. Hence
d = n?/2Therefore, ? = 2d/n
The frequency of the ultrasonic waves is noted as f (Hz)
The experiment is repeated for various n number of maximum and the readings are tabulated.
Knowing the meaning value of ?, the velocity of the ultrasonic waves is calculated.
40

If the distance is now increased or decreased and the variation is exactly one half wavelengths
(?/2) or multiple of it, anode current becomes maximum. From the knowledge of wave length (?) the velocity
v can be obtained using the following relation.
v = f ?
By substituting the value of the density of the given liquid and the velocity of the ultrasonic waves in
the given liquid, the adiabatic compressibility of the given liquid is calculated.





RESULT:
i) Wave length of the ultrasonic waves in the liquid = ---------- m
ii) Velocity of the ultrasonic waves in the liquid = --------- m s-
1
iii) Compressibility of the given liquid = --------- N
-1
m
2








41



1. What are ultrasonic waves?
2. Define Piezo ? Electric effect
3. Explain inverse Piezo ? Electric effect
4. Is ultrasonic wave,an electro-magnetic wave? Explain.
5. What is meant by acoustical grating?
6. Give the properties of ultrasonic waves.
7. What are the methods used to produce ultrasonic waves?
8. What is meant by SONAR?
9. What is meant by Compressibility?
10. What are the applications of ultrasonic waves?


Viva ? voce
FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
2


PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science and fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems and use this knowledge to acquire
higher education.
2. Core competence
To train the students in Engineering Physics so as to apply their knowledge and training to compare,
and to analyze various engineering industrial problems for finding solutions.
3. Breadth
To provide relevant training and experience to bridge the gap between theoretical learning and
practice that enables them to find solutions for the real time problems in industry and to design products.
4. Professionalism
To inculcate professional and effective communication skills, leadership qualities and team spirit for
the students to make them multi-faceted personalities and develop their ability to relate engineering issues
to broader social context.
5. Lifelong learning/ethics
To demonstrate and practice ethical and professional responsibilities in the industry and society by
and large, through commitment and lifelong learning needed for successful professional career.





3


PROGRAMME OUTCOMES (POs)

a) To demonstrate and apply knowledge of Mathematics, Science and Engineering fundamentals in
Engineering physics
b) To determine the Moment of Inertia of given disc and Rigidity modulus of the given wire using
Torsional Pendulum
c) To determine Young?s modulus of a given bar using Non-Uniform bending
d) To utilize laser source and grating to estimate the wave length, particle size of given powder and
Numerical Aperture & acceptance angle of given optical fiber
e) To find the Thermal conductivity of a bad conductor using Lee?s Disc method
f) To Measure the velocity of ultrasonic wave in a liquid and compressibility of the liquid usingultrasonic
Interferometer
g) To determine the wavelength of Hg source using grating and spectrometer
h) To find the thickness of a thin wire using Air- wedge method
i) To participate and succeed in competitive exams and visualize and work on laboratory and
multidisciplinary tasks











4


BS 8161 ? PHYSICSLABORATORY
(Common to all branches of B.E. / B.TechProgrammes)
SYLLABUS


To introduce different experiments to test basic understanding of physics concepts applied in optics, thermal
physics, properties of matter and liquids.

LIST OF EXPERIMENTS: PHYSICS LABORATORY(Any 5 Experiments)
1. Determination of Rigidity modulus ? Torsion pendulum
2. Determination of Young? s modulus by Non uniform bending method
3. (a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
4. Determination of thermal conductivity of a bad conductor ? Lee?s Disc method.
5. Determination of velocity of sound and compressibility of liquid ? Ultrasonic interferometer
6. Determination of wavelength of mercury spectrum ? spectrometer grating
7. Determination of band gap of a semiconductor
8. Determination of thickness of a thin wire ? Air wedge method




Completion of the course, the students will be able to: apply physics principles of optics and thermal physics
to evaluate engineering properties of materials.


COURSE OUTCOMES
COURSE OBJECTIVES
5

BS 8161 ? PHYSICS LABORATORY
CONTENTS

Sl.No. Name of the Experiment (any 5 experiments)
Page
No.
1.
Determination of Rigidity modulus ? Torsion pendulum
6
2.
Determination of Young ?s modulus by Non uniform bending method
12
3.
(a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
18
4.
Determination of thermal conductivity of a bad conductor ? Lee ?s Disc method.
28
5.
Determination of velocity of sound and compressibility of liquid ? Ultrasonic
interferometer
37
6.
Determination of wavelength of mercury spectrum ? spectrometer grating
42
7.
Determination of thickness of a thin wire ? Air wedge method
48
MEASURING INSTRUMENTS
M1 Screw gauge 54
M2 Vernier Calipers 58
M3 Travelling Microscope 62
M4 Spectrometer 66








6

TORSIONAL PENDULUM










7

Expt. No.1 TORSIONAL PENDULUM

AIM:
To determine the moment of inertia of the given disc and hence to determine the rigidity modulus of
the material of the given suspension wire by torsional oscillations
APPARATUS REQUIRED:
Torsional pendulum, two equal masses, stop clock, screw gauge and meter scale

FORMULA:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
where
m ?mass of the cylinder placed on the disc (kg)
To ?period of the pendulum for a length of l without mass (s)
T1?period of the pendulum for the same length when mass m is placed at a distance d 1
from the center of the suspension wire (s)
T2?period of the pendulum for the same length when mass m is placed at a distance d 2
from the center of the suspension wire (s)
a ? radius of the suspension wire (m)




8

1. To determine the time period of the disc:
Length of the wire (l)= --------
2
10
?
? m
Position of the equal
masses
Time for 10 oscillations Time period
(one oscillation)
s
Trial-1
s
Trial-2
s
Mean
s
Without any masses T0
With masses at
d1 = x10
-2
m
T1
With masses at
d2 = x10
-2
m
T2

2. To determine the radius of the wire:
Least count =0 .01 mm. Zero Error ZE = --------- divisions
Zero Correction ZC = ---------- mm

Sl.No.
Pitch Scale
Reading
PSR
3
10
?
? m
Head Scale
Coincidence
HSC
div
Observed reading
OR = PSR + (HSCXLC)
3
10
?
? m
Correct reading
CR = OR ? ZC
3
10
?
? m




Mean = ----------------
3
10
?
? m



9

PROCEDURE:
Torsional pendulum is suspended from vertical chuck. The length of the suspension wire is measured
between the vertical chuck and the chuck attached to the uniform circular disc (i). The circular disc is twisted
slightly without masses on the disc. Now it executes torsional oscillations. Care is taken to see that the disc
oscillates without wobbling. Time taken for 20 oscillations is noted with the help of a stop clock. Two trials are
taken. The average of these two trial readings is calculated from which the period of oscillations is found out
as T0.
Two identical cylindrical masses each of mass m are symmetrically placed on the disc on either side
of the wire at a distance d from the center of the disc. As before the disc is gently twisted. Time taken for 20
oscillations is noted from which the period of oscillation is calculated as T1.
The cylindrical masses are placed at a distance d2 from the center and the experiment is repeated.
The mean time period of oscillations is calculated T2.
The diameter of the specimen wire is measured accurately with the help of the screw gauge, at
various places on the wire. The average diameter and hence the radius of the wire is calculated as r.
Moment of inertia and the rigidity modulus are determined by the substituting the value of m, T 0, T1, T2,
T3, and l in the formula.










10

CALCULATION:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2

Mass of cylindrical mass, m = ----------- ? 10
-3
kg
Closest distance of the mass from the centre of the suspension wire, d1 = ------------ ? 10
-2
m
Farthest distance of the mass from the centre of suspension wire, d2= ------------? 10
-2
m
Period of oscillation without mass, To = ------------- s
Period of oscillation with mass at d1, T1= ------------ s
Period of oscillation with mass at d2, T2 = ------------- s

Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
= --------------- kg m
2
= --------------- kg m
2

Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
Moment of inertia, I = ------------------ kg m
2
Length of the wire, l = ------------------- ? 10
-2
m
Time of oscillation, To = ------------------ s
Radius of the wire, a = ------------------- ? 10
-3
m
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
= ----------------------
Rigidity modulus, n = ------------------- Nm
-2
11









RESULT:
(i)
The moment of inertia of the given circular disc, I = --------------- kg m
2
(ii)
The rigidity modulus of the material of the given wire, n = -------------- Nm
-2




1. State Hooke?s law.
2. Define ?Rigidity modulus
3. Define ?Moment of inertia
4. What is meant by torsional oscillation?
5. What is period of oscillation?
6. What is meant by twisting couple?
7. Define ? Shearing stress
8. Define ? Shearing strain
9. What is the unit of rigidity modulus?
10. What are the applications of torsional pendulum?


Viva ? voce
12


Young?s Modulus ? Non Uniform Bending
To determine depression (y):
L.C =.001cm M = ___________
3
10
?
? kg

Sl.No

Load


3
10
?
?
k
g
Microscope reading
Mean

2
10
?
? m
Depression
y for M kg

2
10
?
? m
Loading Unloading
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
1 W
2 W+50
3 W+100
4 W+150
5 W+200
6 W+250

Mean (y) = ----------
2
10
?
? m





13

Expt. No.2 YOUNG?S MODULUS BY NON ? UNIFORM BENDING
AIM:
To determine the young?s modulus of the material of the given bar, by non-uniform bending method
APPARATUS REQUIRED:
Travelling microscope, wooden bar, knife- edge, weights hanger, slotted weight, vernier calipers,
screw gauge and pin
FORMULA:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Where,
g ? acceleration due to gravity (9.8 ms
-2
)
l ? length of the bar between two knife edges (m)
b ? breadth of the bar (m)
d ? thickness of the bar (m)
y ? depressiont in the scale reading due to the change of mass M (m)
PROCEDURE:
The given wooden bar, for which young?s modulus is to be determined, is paced symmetrically on the
two knife edges. The distance between the knife edges is measured as the length of the bar (l). It is adjusted
to be, say, 60 cm. the weight hanger is suspended at the centre of the bar. A pin is held vertically at the
centre of the bar with the help of wax.
The given bar is brought to elastic mood by loading and unloading the bar with slotted weights in steps
of 50 g. This is repeated for two or three times. With the hanger as dead load W, the microscope is focused on
to the tip of the pin. The tangential screw of the microscope is adjusted so that the image of the tip of the pin
just touches the horizontal cross wire of the eyepiece. The main scale reading and the vernier scale
coincidence corresponding to this position are noted.
14

To find the breadth using vernier calipers, b:
Least count = ---------- cm Zero error = --------- div.
= ---------- ?10
-2
m Zero correction = ?ZE ?LC= --------- ?10
-2
m
Sl. No.

MSR
x 10
-2
m

VSC
div.
Observed reading
OR = MSR+(VSC ? LC)
x 10
-2
m
Correct Reading
CR = OR ? ZC
x 10
-2
m
1.

2.

3.


Mean, b = ------------------------?10
-2
m
To find the thickness using screw gauge, d:
Least count = ---------- mm Zero error = --------- div.
= ---------- ?10
-3
m Zero correction =ZE ?LC= --------- ?10
-3
m
Sl. No.

PSR
x 10
-3
m

HSC
div.
Observed reading
OR = PSR+ (HSC ? LC)
x 10
-3
m
Correct Reading
CR = OR ? ZC
x 10
-3
m
1.

2.

3.


Mean, d = ---------------------------?10
-3
m
15


The experiment is repeated by adding weights in steps of 50 g and every time the microscope is
adjusted for coincidence. The corresponding readings are noted. The experiment is repeated by unloading the
weights in steps of 50 g and the corresponding readings are tabulated. From this table, the shift in the scale
reading, say y, for a change of mass M is found out.
The breadth of the bar is measured at various points with the help of vernier calipers. Similarly the
thickness of the bar is measured by screw gauge. Substituting the values of M, y, l, d, b and g in the formula,
the young?s modulus of the material of the given bar is calculated.

















16

CALCULATION:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Acceleration due to gravity, g = 9.8 ms
-2
Length of the bar between two knife edges, l = ------------ ?10
-2
m
Breadth of the bar, b = ----------- ?10
-2
m
Thickness of the bar, d = ----------- ?10
-3
m
y = -----------?10
-2
m
E =
???? ?? 2
4?? ?? 3
?? Nm
-2

= ---------------
Young?s modulus, E = ----------- Nm
-2












17








RESULT:
Young?s modulus of the material of the given bar, E = ---------- Nm
-2


1. Define ? Young?s modulus
2. What is meant by Non-uniform bending?
3. Define ? Stress and strain
4. State Hooke?s law.
5. Define ? Neutral axis
6. What is the SI unit of young?s modulus?
7. Define ? Elastic limit
8. Define ? Elasticity
9. What are the factors affecting elasticity?
10. Define ? Elastic fatigue

Viva ? voce
18


To find the wavelength of the laser beam, ?:
Distance between the screen and the grating, D = ------------?10
-2
m
Number of lines per meter length of the grating, N = --------------- Lines per meter
Sl. No.
Order of diffraction,
(m)
Reading of the diffracted image
(?10
-2
m)
?? ?? = ?????? ?1
(
?? ?? ?? )
(deg.)
? =
?????? ?? ?? ????
m

Left side
(xi)
Right side
(xr)
Mean
(xm)










Mean, ? = ---------------- m


19

Expt. No.3(a) WAVELENGTH OF LASER LIGHT AND PARTICLE SIZE


AIM:
(i) To determine the wavelength of the given laser light.
(ii) To determine size of the given particle.
APPARATUS REQUIRED:
Diode laser, grating, screen, given micro particles, scale and screen.
FORMULAE:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
(ii) Grain size or diameter of the grain, 2d =
?????? ?? ?? m
Where
?? ?? ?angle of diffraction (deg.)
M ?order of diffraction (No unit)
N ?number of lines per metre length of the grating (m
-3
)
n ? order of diffraction (no unit)
? ? wavelength of laser light used (m)
D ? distance between the glass plate and the screen (m)
?? ?? - distance between the central bright spot and the nth fringe (m)
PROCEDURE:
TO FIND THE WAVELENGTH OF THE GIVEN LASER LIGHT:
The laser source, grating and screen are placed properly as shown in figure. The diode laser is kept
horizontally and switched on. Extreme care should be taken to avoid direct exposure of laser light on eyes.
20











21

The grating is held normal to the laser beam by adjusting the grating in such a way that the reflected
laser beam from the grating coincides with incident laser beam. Now the diffracted laser spots of various
orders can be seen on the screen, placed on the other side of the grating.

The distance of the different orders on either side of the central spot are measured as x randxi and are
tabulated.The mean value of xrandxiare calculated as xm for the m
th
order diffracted light. The distance
between the grating and the screen is measured as D. Hence, the angle of diffraction for the m
th
order,
?? ?? = ?????? ?1
(
?? ?? ?? )
The experiment is repeated for different orders and the readings are tabulated. From the table, ? for
each order is calculated. Substituting the value of ?, the corresponding order of diffraction and the number of
lines per meter length of the grating, the wavelength is calculated.

TO FIND THE SIZE OF THE GIVEN MICRO PARTICLE:

The lycopodium powder having fine micro particles of nearly same size is sprinkled on a glass plate.
This glass plate is kept between laser source and screen.
Now the particles present in the glass plate diffract laser beam from the source. By adjusting the
distance between the glass plate and the screen, a circular fringe pattern is obtained on the screen with
different orders of fingers. Now distance between the screen and the glass plate (D) is measured.
The distance of the first order and the second order fringe from the centre of spot are also measured.
Using the formula, the particle size is found out. The experiment is repeated for different D values.
22

To find the size of the particle:

CALCULATION:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
Number of lines per metre in the grating, N = ------------ lines per metre.
First order, m1; ?? 1
= ------------
Wavelength, ? =
?????? ?? 1
????
= ------------
Second order, m2; ?? 2
= ------------
Wavelength, ? =
?????? ?? 2
????
= ------------
Third order, m3; ?? 3
= ------------
Wavelength, ? =
?????? ?? 3
????
= ------------
Fourth order, m4; ?? 4
= ------------
Wavelength, ? =
?????? ?? 4
????
= -------------
Fifth order, m5; ?? 5
= ------------

Sl.No



Distance between
screen and glass
plate(D)
2
10
?
? m
Order of
diffraction
(n)
Distance between the
central bright spot and n
th

fringe (xn )
2
10
?
? m
Particle size
2
n
nD
d
x
?
?
m






23

Wavelength, ? =
?????? ?? 4
????
= ------------
Mean wavelength of the given laser light, ? = -------------- m
(ii) Grain size or diameter of the grain. 2d =
?????? ?? ??
Order of differaction, n = --------------
Wavelength of laser light used, ? = ------------- m
Distance between glass plate and the screen, D = ------------ m
Distance between central bright spot and the n
th
fringe,?? ?? = ------------ m
2d =
?????? ?? ??
=
= ------------ m








RESULT:
(i) Wavelength of the laser beam, ? = -------------- m
(ii) Average size of the particle = --------------- m

24


Optical fiber

To find numerical aperture, NA:

Sl. No.
Diameter of the circular patch
D(m)
Distance between the tip of the
fiber and the screen X (m)
NA =
?? (4?? 2
+?? 2
)
1
2





Mean NA =
Therefore, the acceptance angle, ? = Sin
-1
(NA) = -------------------
= -------------------


25

Expt. No.3(b) NUMERICAL APERTURE AND ACCEPTANCE ANGLE
AIM:
To measure the numerical aperture and the acceptance angle of the given fiber cable
APPARATUS REQUIRED:
Optical fiber cable with source, NA jig and in-line adaptor
FORMULA:
The numerical aperture, NA =
?? (4?? 2
+?? 2
)
1
2

Acceptance angle, ? = Sin
-1
(NA)
where,
D ? diameter of the circular patch (m)
X ? distance between the tip of the fiber and the screen (m)
PROCEDURE:
One end of the one metre fiber cable is connected to the laser light source and the other end
to the NA jig as shown in figure. The AC main is plugged in and the laser light is adjusted so that it appears at
the end of the fiber on the NA jig, the intensity knob is adjusted to get maximum intensity.
The white screen with the four concentric circles (10 mm, 20 mm, 30 mm and 40 mm diameter) is held
vertically at a suitable distance to make the red spot from the emitting fiber coincides with the 10 mm circle,
the diameter (D) of the spot is noted. The distance (X) of the screen from the fiber end is recorded.
The procedure is repeated for 20 mm, 30 mm, 40 mm diameter circles and the readings are tabulated.




26

















RESULT:
The numerical aperture, NA = ----------------
Acceptance angle, ? = ----------------




27




1. What is semiconductor diode laser?
2. What is meant by active material in laser?
3. What is meant by LASER?
4. What is stimulated emission?
5. What are the characteristics of laser radiation?
6. What is homo?junction laser?
7. What is hetero?junction laser?
8. What are the applications of semiconductor laser?
9. What are the conditions required for laser action?
10. Define ? Numerical aperture







Viva ? voce
28


Lee?s disc setup


29

Expt. No. 4 THERMAL CONDUCTIVITY OF A BAD CONDUCTOR
BY LEE?S DISC METHOD

AIM:
To determine the coefficient of thermal conductivity of a bad conductor
APPARATUS REQUIRED:
Lee?s disc apparatus, bad conductors, stop-clock, thermometers, screw gauge, vernier calipers and
steam boiler
FORMULA:
Thermal conductivity of a bad conductor,
? ?
? ? ? ?
1 1
2 1
2
2 2
2
? ?
? ?
?
?
?
?
?
?
?
?
?
? k Wm
h r r
h r d
dt
d
MS
K
? ? ?
?

M ? Mass of the metallic disc (Kg)
S ? Specific heat capacity of the metallic disc ( J Kg
-1
K
-1
)
? rate of cooling at steady temperature (
o
C/s)
d ? thickness of the bad conductor (m)
h ? thickness of the metallic disc (m)
r?radius of the metallic disc (m)
1
? ? steady temperature of the steam chamber (
o
C)
2
? ? steady temperature of the Metallic disc (
o
C)

PROCEDURE:
The thickness of the bad conductor say card board and thickness of the metallic disc are determined
using a screw gauge. The radius of the metallic disc is found using a vernier caliper. The mass of a metallic
disc is also found using a common balance. The readings are tabulated.

30

To find the radius of the metallic disc (r) using Vernier Calipers
Least count = 0.01cm Zero error = ? ???div
Zero correction = ? ???cm
= --------- ?10
-2
m
Sl.No.
MSR
(x10
-2
m)
VSC
(div.)
OR = MSR +(VSC x LC)
(x10
-2
m)
CR = OR ? ZC
(x10
-2
m)
1
2
3
4

Mean radius, r = --------------------------------- x10
-2
m
To find the thickness of the bad conductor (d) using Screw gauge
Least count = 0.01mm Zero error = ? ???div
Zero correction = ? ???mm
Sl.No.
PSR
(x10
-3
m)
HSC
(div.)
OR = PSR + (HSC x LC)
(x10
-3
m)
CR = OR ? ZC
(x10
-3
m)
1.
2.
3.
4.

Mean, d = -------------------------------- x10
-3
m
31

The whole Lee?s disc apparatus is suspended from a stand as shown in the figure. The given bad
conductor is placed in between the metallic disc and the steam chamber. Two thermometers T1 and T2 are
inserted into the respective holes.
Steam from the steam boiler is passed into the steam chamber until the temperature of the steam
chamber and the metallic disc are steady. The Steady temperature (?1) of the steam chamber and (?2) of the
metallic disc recorded by the thermometers are noted.
Now the bad conductor is removed and the steam chamber is placed in direct contact with the metallic
disc. The temperature of the disc rapidly rises. When the temperature of the disc rises about 10
o
Cabove
?2
o
C, the steam chamber is carefully removed after cutting of the steam supply.
When the temperature of the disc reaches 10
o
C above the steady temperature of the disc i.e. (?2+
10)
o
C , stop clock is started. Time for every one degree celsius fall of temperature is noted until the metallic
disc attains a temperature (?2 - 10)
o
C.
A graph is drawn taking time along the x-axis and temperature along the y-axis. The cooling curve is
obtained .To obtain the rate of the cooling (
????
????
)
?? 2
from this graph, a triangle is drawn by taking 1
o
C above
and 1
o
Cbelow the steady temperature ?2. Then the slope AB / BC gives the rate of cooling at(
????
????
)
?? 2
. From
these readings and using the given formula thermal conductivity of the given bad conductor is calculated.










32

To find the thickness of the metallic disc (h) using screw gauge
Least count = 0.01mm Zero error = ? ???div
Zero correction = ? ???mm
Sl.No.
PSR
(x10
-3
m)
HSC
(div.)
TR = PSR + (HSC x LC)
(x10
-3
m)
Corrected reading
CR = TR ? ZC
(x10
-3
m)
1
2
3
4
5

Mean, h = ------------------------------ x10
-3
m
To determine the rate of cooling of metallic disc:
Time
s
Temperature
o
C
Time
s
Temperature
o
C







33

CALCULATION:
Mass of the disc, m= ---------- x10
-3
kg
Specific heat capacity of the disc,c = 385 J kg
-1
K
-1
Rate of cooling at ?2,
????
????
= -------------- deg s
-1
Radius of the disc, r = ---------- x10
-2
m
Height of the disc, h = ---------- x10
-2
m
Thickness of the bad conductor, d = ---------- x10
-3 m
Temperature of steam, ?1 = ---------
o
C
Steady temperature of the disc, ?2 = -------------
o
C
Thermal conductivity,
? ?
? ? ? ?
1 1
2 1
2
2 2
2
? ?
? ?
?
?
?
?
?
?
?
?
?
? k Wm
h r r
h r d
dt
d
MS
K
? ? ?
?


= --------------------

= -------------------- Wm
-1
K
-1








34
















RESULT:
The thermal conductivity of the given bad conductor by Lee?s disc method, K = -------------- Wm
-1
K
-1







35





1. What is meant by thermal conductivity?
2. What is meant by Rate of cooling?
3. Does the value of thermal conductivity depend on the dimension of the specimen?
4. Is there any reason to take the specimen in the form of a disc?
5. Can this method be used for good conductors?
6. What is lee's disc method?
7. What are the differences between good conductor and bad conductor?
8. What are the methods used to determine thermal conductivity of bad conductor?
9. What is meant by steady temperature?
10. What is meant by specific heat capacity?

Viva ? voce
36




37


Exp. No. 5 ULTRASONIC INTERFEROMETER

AIM:
To determine the velocity of the ultrasonic waves in a given liquid and to find the compressibility of
the liquid using ultrasonic interferometer
APPARATUS REQUIRED:
Ultrasonic interferometer (high frequency) generator, measuring cell, the experimental liquid
and coaxial cables
FORMULA:
1) Velocity of the ultrasonic waves v = f ? ms
-1
where,
f ?frequency of the ultrasonic waves (Hz)
? ? wavelength of the ultrasonic waves in the liquid (m)

2) Compressibility of the liquid ? =
1
?? 2
?? m
2
N
-1
where
? ? density of the given liquid (kg m
-3
)
v? velocity of the ultrasonic waves with in the liquid (m s
-1
)
DESCRIPTION:
The interferometer consists of (i) high frequency generator and (ii) measuring cell. The high
frequency generator is used to excite the quartz plate fixed at the bottom of the measuring cell.
The exited quartz plate generates ultrasonic waves in the experimental liquid contained in the cell. A micro
ammeter is provided to observe the change in the current.
Two control knobs are also provided in the generator for the purpose of sensitivity regulation and also
adjustment. The measuring cell is a double walled cell to maintain constant temperature during

38


To find the wavelength of the ultrasonic waves in the liquid:

Order of
maximum current

Micrometer reading
Distance for n
maximum current, d
(x10
-3
m)
Wavelength
?=2d/n
(x10
-3
m)
PSR
(x10
-3
m)
HSR
(div)
TR
(x10
-3
m)

x
x+n
x+2n
x+3n



Wavelength, ? = ------------------ x10
-3
m
Frequency of ultrasonic waves = 2 MHz

CALCULATION:
1) The Velocity of the ultrasonic waves, v = f?
= ---------- m s
-1
The density of the given liquid ? = ---------- kg m
-3
2) Adiabatic compressibility of the liquid, ? =
1
?? 2
??
= -----------
Adiabatic compressibility of the liquid, ? = --------------


39

experiment.A fine micrometer arrangement is fixed at the top of the interferometer, enables the reflector
pates to move upward or downward through a known distance.
PRINCIPLE:
The velocity of the ultrasonic waves is determined using the interferometer. The principle used in the
measurement of velocity is based on the accurate determination of the wave length (?) of ultrasonic waves
in the liquid. The ultrasonic waves are reflected back by a removable metallic plate parallel to the crystal
.These two ultrasonic waves superimpose producing stationary wave pattern within the medium.

If the separation between these two plates is exactly an integral multiple of ?/2 of the ultrasonic
waves, acoustic resonance is produced in the standing waves.

This acoustic resonance gives rise to an electrical reaction on the generator and the anode current of the
generator becomes maximum.
PROCEDURE:
The measuring cell is connected to the output terminal of the high frequency generator through a
shielded cable. The cell is filled with an experimental liquid before switching on the generator. The
ultrasonic waves move normally from the quartz crystal till they are reflected back from the movable plate
and the standing waves are formed in the liquid in between the reflector plate and the quartz crystal.
The micrometer is slowly moved till the anode current of the high frequency generator shows a
maximum in the meter. Now the initial reading of the micrometer screw is noted. If the micrometer is rotated
in the same direction, the current various between minimum and maximum.Micrometer screw is rotated in
the same direction until n
th
maximum in the micro ammeter is reached. The reading in the micrometer is
noted.
For n number of maximum anode current, the distance moved (d) is measured with the help of
micrometer. Hence
d = n?/2Therefore, ? = 2d/n
The frequency of the ultrasonic waves is noted as f (Hz)
The experiment is repeated for various n number of maximum and the readings are tabulated.
Knowing the meaning value of ?, the velocity of the ultrasonic waves is calculated.
40

If the distance is now increased or decreased and the variation is exactly one half wavelengths
(?/2) or multiple of it, anode current becomes maximum. From the knowledge of wave length (?) the velocity
v can be obtained using the following relation.
v = f ?
By substituting the value of the density of the given liquid and the velocity of the ultrasonic waves in
the given liquid, the adiabatic compressibility of the given liquid is calculated.





RESULT:
i) Wave length of the ultrasonic waves in the liquid = ---------- m
ii) Velocity of the ultrasonic waves in the liquid = --------- m s-
1
iii) Compressibility of the given liquid = --------- N
-1
m
2








41



1. What are ultrasonic waves?
2. Define Piezo ? Electric effect
3. Explain inverse Piezo ? Electric effect
4. Is ultrasonic wave,an electro-magnetic wave? Explain.
5. What is meant by acoustical grating?
6. Give the properties of ultrasonic waves.
7. What are the methods used to produce ultrasonic waves?
8. What is meant by SONAR?
9. What is meant by Compressibility?
10. What are the applications of ultrasonic waves?


Viva ? voce
42



Normal Incidence Angle of diffraction






FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
2


PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science and fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems and use this knowledge to acquire
higher education.
2. Core competence
To train the students in Engineering Physics so as to apply their knowledge and training to compare,
and to analyze various engineering industrial problems for finding solutions.
3. Breadth
To provide relevant training and experience to bridge the gap between theoretical learning and
practice that enables them to find solutions for the real time problems in industry and to design products.
4. Professionalism
To inculcate professional and effective communication skills, leadership qualities and team spirit for
the students to make them multi-faceted personalities and develop their ability to relate engineering issues
to broader social context.
5. Lifelong learning/ethics
To demonstrate and practice ethical and professional responsibilities in the industry and society by
and large, through commitment and lifelong learning needed for successful professional career.





3


PROGRAMME OUTCOMES (POs)

a) To demonstrate and apply knowledge of Mathematics, Science and Engineering fundamentals in
Engineering physics
b) To determine the Moment of Inertia of given disc and Rigidity modulus of the given wire using
Torsional Pendulum
c) To determine Young?s modulus of a given bar using Non-Uniform bending
d) To utilize laser source and grating to estimate the wave length, particle size of given powder and
Numerical Aperture & acceptance angle of given optical fiber
e) To find the Thermal conductivity of a bad conductor using Lee?s Disc method
f) To Measure the velocity of ultrasonic wave in a liquid and compressibility of the liquid usingultrasonic
Interferometer
g) To determine the wavelength of Hg source using grating and spectrometer
h) To find the thickness of a thin wire using Air- wedge method
i) To participate and succeed in competitive exams and visualize and work on laboratory and
multidisciplinary tasks











4


BS 8161 ? PHYSICSLABORATORY
(Common to all branches of B.E. / B.TechProgrammes)
SYLLABUS


To introduce different experiments to test basic understanding of physics concepts applied in optics, thermal
physics, properties of matter and liquids.

LIST OF EXPERIMENTS: PHYSICS LABORATORY(Any 5 Experiments)
1. Determination of Rigidity modulus ? Torsion pendulum
2. Determination of Young? s modulus by Non uniform bending method
3. (a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
4. Determination of thermal conductivity of a bad conductor ? Lee?s Disc method.
5. Determination of velocity of sound and compressibility of liquid ? Ultrasonic interferometer
6. Determination of wavelength of mercury spectrum ? spectrometer grating
7. Determination of band gap of a semiconductor
8. Determination of thickness of a thin wire ? Air wedge method




Completion of the course, the students will be able to: apply physics principles of optics and thermal physics
to evaluate engineering properties of materials.


COURSE OUTCOMES
COURSE OBJECTIVES
5

BS 8161 ? PHYSICS LABORATORY
CONTENTS

Sl.No. Name of the Experiment (any 5 experiments)
Page
No.
1.
Determination of Rigidity modulus ? Torsion pendulum
6
2.
Determination of Young ?s modulus by Non uniform bending method
12
3.
(a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
18
4.
Determination of thermal conductivity of a bad conductor ? Lee ?s Disc method.
28
5.
Determination of velocity of sound and compressibility of liquid ? Ultrasonic
interferometer
37
6.
Determination of wavelength of mercury spectrum ? spectrometer grating
42
7.
Determination of thickness of a thin wire ? Air wedge method
48
MEASURING INSTRUMENTS
M1 Screw gauge 54
M2 Vernier Calipers 58
M3 Travelling Microscope 62
M4 Spectrometer 66








6

TORSIONAL PENDULUM










7

Expt. No.1 TORSIONAL PENDULUM

AIM:
To determine the moment of inertia of the given disc and hence to determine the rigidity modulus of
the material of the given suspension wire by torsional oscillations
APPARATUS REQUIRED:
Torsional pendulum, two equal masses, stop clock, screw gauge and meter scale

FORMULA:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
where
m ?mass of the cylinder placed on the disc (kg)
To ?period of the pendulum for a length of l without mass (s)
T1?period of the pendulum for the same length when mass m is placed at a distance d 1
from the center of the suspension wire (s)
T2?period of the pendulum for the same length when mass m is placed at a distance d 2
from the center of the suspension wire (s)
a ? radius of the suspension wire (m)




8

1. To determine the time period of the disc:
Length of the wire (l)= --------
2
10
?
? m
Position of the equal
masses
Time for 10 oscillations Time period
(one oscillation)
s
Trial-1
s
Trial-2
s
Mean
s
Without any masses T0
With masses at
d1 = x10
-2
m
T1
With masses at
d2 = x10
-2
m
T2

2. To determine the radius of the wire:
Least count =0 .01 mm. Zero Error ZE = --------- divisions
Zero Correction ZC = ---------- mm

Sl.No.
Pitch Scale
Reading
PSR
3
10
?
? m
Head Scale
Coincidence
HSC
div
Observed reading
OR = PSR + (HSCXLC)
3
10
?
? m
Correct reading
CR = OR ? ZC
3
10
?
? m




Mean = ----------------
3
10
?
? m



9

PROCEDURE:
Torsional pendulum is suspended from vertical chuck. The length of the suspension wire is measured
between the vertical chuck and the chuck attached to the uniform circular disc (i). The circular disc is twisted
slightly without masses on the disc. Now it executes torsional oscillations. Care is taken to see that the disc
oscillates without wobbling. Time taken for 20 oscillations is noted with the help of a stop clock. Two trials are
taken. The average of these two trial readings is calculated from which the period of oscillations is found out
as T0.
Two identical cylindrical masses each of mass m are symmetrically placed on the disc on either side
of the wire at a distance d from the center of the disc. As before the disc is gently twisted. Time taken for 20
oscillations is noted from which the period of oscillation is calculated as T1.
The cylindrical masses are placed at a distance d2 from the center and the experiment is repeated.
The mean time period of oscillations is calculated T2.
The diameter of the specimen wire is measured accurately with the help of the screw gauge, at
various places on the wire. The average diameter and hence the radius of the wire is calculated as r.
Moment of inertia and the rigidity modulus are determined by the substituting the value of m, T 0, T1, T2,
T3, and l in the formula.










10

CALCULATION:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2

Mass of cylindrical mass, m = ----------- ? 10
-3
kg
Closest distance of the mass from the centre of the suspension wire, d1 = ------------ ? 10
-2
m
Farthest distance of the mass from the centre of suspension wire, d2= ------------? 10
-2
m
Period of oscillation without mass, To = ------------- s
Period of oscillation with mass at d1, T1= ------------ s
Period of oscillation with mass at d2, T2 = ------------- s

Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
= --------------- kg m
2
= --------------- kg m
2

Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
Moment of inertia, I = ------------------ kg m
2
Length of the wire, l = ------------------- ? 10
-2
m
Time of oscillation, To = ------------------ s
Radius of the wire, a = ------------------- ? 10
-3
m
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
= ----------------------
Rigidity modulus, n = ------------------- Nm
-2
11









RESULT:
(i)
The moment of inertia of the given circular disc, I = --------------- kg m
2
(ii)
The rigidity modulus of the material of the given wire, n = -------------- Nm
-2




1. State Hooke?s law.
2. Define ?Rigidity modulus
3. Define ?Moment of inertia
4. What is meant by torsional oscillation?
5. What is period of oscillation?
6. What is meant by twisting couple?
7. Define ? Shearing stress
8. Define ? Shearing strain
9. What is the unit of rigidity modulus?
10. What are the applications of torsional pendulum?


Viva ? voce
12


Young?s Modulus ? Non Uniform Bending
To determine depression (y):
L.C =.001cm M = ___________
3
10
?
? kg

Sl.No

Load


3
10
?
?
k
g
Microscope reading
Mean

2
10
?
? m
Depression
y for M kg

2
10
?
? m
Loading Unloading
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
1 W
2 W+50
3 W+100
4 W+150
5 W+200
6 W+250

Mean (y) = ----------
2
10
?
? m





13

Expt. No.2 YOUNG?S MODULUS BY NON ? UNIFORM BENDING
AIM:
To determine the young?s modulus of the material of the given bar, by non-uniform bending method
APPARATUS REQUIRED:
Travelling microscope, wooden bar, knife- edge, weights hanger, slotted weight, vernier calipers,
screw gauge and pin
FORMULA:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Where,
g ? acceleration due to gravity (9.8 ms
-2
)
l ? length of the bar between two knife edges (m)
b ? breadth of the bar (m)
d ? thickness of the bar (m)
y ? depressiont in the scale reading due to the change of mass M (m)
PROCEDURE:
The given wooden bar, for which young?s modulus is to be determined, is paced symmetrically on the
two knife edges. The distance between the knife edges is measured as the length of the bar (l). It is adjusted
to be, say, 60 cm. the weight hanger is suspended at the centre of the bar. A pin is held vertically at the
centre of the bar with the help of wax.
The given bar is brought to elastic mood by loading and unloading the bar with slotted weights in steps
of 50 g. This is repeated for two or three times. With the hanger as dead load W, the microscope is focused on
to the tip of the pin. The tangential screw of the microscope is adjusted so that the image of the tip of the pin
just touches the horizontal cross wire of the eyepiece. The main scale reading and the vernier scale
coincidence corresponding to this position are noted.
14

To find the breadth using vernier calipers, b:
Least count = ---------- cm Zero error = --------- div.
= ---------- ?10
-2
m Zero correction = ?ZE ?LC= --------- ?10
-2
m
Sl. No.

MSR
x 10
-2
m

VSC
div.
Observed reading
OR = MSR+(VSC ? LC)
x 10
-2
m
Correct Reading
CR = OR ? ZC
x 10
-2
m
1.

2.

3.


Mean, b = ------------------------?10
-2
m
To find the thickness using screw gauge, d:
Least count = ---------- mm Zero error = --------- div.
= ---------- ?10
-3
m Zero correction =ZE ?LC= --------- ?10
-3
m
Sl. No.

PSR
x 10
-3
m

HSC
div.
Observed reading
OR = PSR+ (HSC ? LC)
x 10
-3
m
Correct Reading
CR = OR ? ZC
x 10
-3
m
1.

2.

3.


Mean, d = ---------------------------?10
-3
m
15


The experiment is repeated by adding weights in steps of 50 g and every time the microscope is
adjusted for coincidence. The corresponding readings are noted. The experiment is repeated by unloading the
weights in steps of 50 g and the corresponding readings are tabulated. From this table, the shift in the scale
reading, say y, for a change of mass M is found out.
The breadth of the bar is measured at various points with the help of vernier calipers. Similarly the
thickness of the bar is measured by screw gauge. Substituting the values of M, y, l, d, b and g in the formula,
the young?s modulus of the material of the given bar is calculated.

















16

CALCULATION:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Acceleration due to gravity, g = 9.8 ms
-2
Length of the bar between two knife edges, l = ------------ ?10
-2
m
Breadth of the bar, b = ----------- ?10
-2
m
Thickness of the bar, d = ----------- ?10
-3
m
y = -----------?10
-2
m
E =
???? ?? 2
4?? ?? 3
?? Nm
-2

= ---------------
Young?s modulus, E = ----------- Nm
-2












17








RESULT:
Young?s modulus of the material of the given bar, E = ---------- Nm
-2


1. Define ? Young?s modulus
2. What is meant by Non-uniform bending?
3. Define ? Stress and strain
4. State Hooke?s law.
5. Define ? Neutral axis
6. What is the SI unit of young?s modulus?
7. Define ? Elastic limit
8. Define ? Elasticity
9. What are the factors affecting elasticity?
10. Define ? Elastic fatigue

Viva ? voce
18


To find the wavelength of the laser beam, ?:
Distance between the screen and the grating, D = ------------?10
-2
m
Number of lines per meter length of the grating, N = --------------- Lines per meter
Sl. No.
Order of diffraction,
(m)
Reading of the diffracted image
(?10
-2
m)
?? ?? = ?????? ?1
(
?? ?? ?? )
(deg.)
? =
?????? ?? ?? ????
m

Left side
(xi)
Right side
(xr)
Mean
(xm)










Mean, ? = ---------------- m


19

Expt. No.3(a) WAVELENGTH OF LASER LIGHT AND PARTICLE SIZE


AIM:
(i) To determine the wavelength of the given laser light.
(ii) To determine size of the given particle.
APPARATUS REQUIRED:
Diode laser, grating, screen, given micro particles, scale and screen.
FORMULAE:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
(ii) Grain size or diameter of the grain, 2d =
?????? ?? ?? m
Where
?? ?? ?angle of diffraction (deg.)
M ?order of diffraction (No unit)
N ?number of lines per metre length of the grating (m
-3
)
n ? order of diffraction (no unit)
? ? wavelength of laser light used (m)
D ? distance between the glass plate and the screen (m)
?? ?? - distance between the central bright spot and the nth fringe (m)
PROCEDURE:
TO FIND THE WAVELENGTH OF THE GIVEN LASER LIGHT:
The laser source, grating and screen are placed properly as shown in figure. The diode laser is kept
horizontally and switched on. Extreme care should be taken to avoid direct exposure of laser light on eyes.
20











21

The grating is held normal to the laser beam by adjusting the grating in such a way that the reflected
laser beam from the grating coincides with incident laser beam. Now the diffracted laser spots of various
orders can be seen on the screen, placed on the other side of the grating.

The distance of the different orders on either side of the central spot are measured as x randxi and are
tabulated.The mean value of xrandxiare calculated as xm for the m
th
order diffracted light. The distance
between the grating and the screen is measured as D. Hence, the angle of diffraction for the m
th
order,
?? ?? = ?????? ?1
(
?? ?? ?? )
The experiment is repeated for different orders and the readings are tabulated. From the table, ? for
each order is calculated. Substituting the value of ?, the corresponding order of diffraction and the number of
lines per meter length of the grating, the wavelength is calculated.

TO FIND THE SIZE OF THE GIVEN MICRO PARTICLE:

The lycopodium powder having fine micro particles of nearly same size is sprinkled on a glass plate.
This glass plate is kept between laser source and screen.
Now the particles present in the glass plate diffract laser beam from the source. By adjusting the
distance between the glass plate and the screen, a circular fringe pattern is obtained on the screen with
different orders of fingers. Now distance between the screen and the glass plate (D) is measured.
The distance of the first order and the second order fringe from the centre of spot are also measured.
Using the formula, the particle size is found out. The experiment is repeated for different D values.
22

To find the size of the particle:

CALCULATION:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
Number of lines per metre in the grating, N = ------------ lines per metre.
First order, m1; ?? 1
= ------------
Wavelength, ? =
?????? ?? 1
????
= ------------
Second order, m2; ?? 2
= ------------
Wavelength, ? =
?????? ?? 2
????
= ------------
Third order, m3; ?? 3
= ------------
Wavelength, ? =
?????? ?? 3
????
= ------------
Fourth order, m4; ?? 4
= ------------
Wavelength, ? =
?????? ?? 4
????
= -------------
Fifth order, m5; ?? 5
= ------------

Sl.No



Distance between
screen and glass
plate(D)
2
10
?
? m
Order of
diffraction
(n)
Distance between the
central bright spot and n
th

fringe (xn )
2
10
?
? m
Particle size
2
n
nD
d
x
?
?
m






23

Wavelength, ? =
?????? ?? 4
????
= ------------
Mean wavelength of the given laser light, ? = -------------- m
(ii) Grain size or diameter of the grain. 2d =
?????? ?? ??
Order of differaction, n = --------------
Wavelength of laser light used, ? = ------------- m
Distance between glass plate and the screen, D = ------------ m
Distance between central bright spot and the n
th
fringe,?? ?? = ------------ m
2d =
?????? ?? ??
=
= ------------ m








RESULT:
(i) Wavelength of the laser beam, ? = -------------- m
(ii) Average size of the particle = --------------- m

24


Optical fiber

To find numerical aperture, NA:

Sl. No.
Diameter of the circular patch
D(m)
Distance between the tip of the
fiber and the screen X (m)
NA =
?? (4?? 2
+?? 2
)
1
2





Mean NA =
Therefore, the acceptance angle, ? = Sin
-1
(NA) = -------------------
= -------------------


25

Expt. No.3(b) NUMERICAL APERTURE AND ACCEPTANCE ANGLE
AIM:
To measure the numerical aperture and the acceptance angle of the given fiber cable
APPARATUS REQUIRED:
Optical fiber cable with source, NA jig and in-line adaptor
FORMULA:
The numerical aperture, NA =
?? (4?? 2
+?? 2
)
1
2

Acceptance angle, ? = Sin
-1
(NA)
where,
D ? diameter of the circular patch (m)
X ? distance between the tip of the fiber and the screen (m)
PROCEDURE:
One end of the one metre fiber cable is connected to the laser light source and the other end
to the NA jig as shown in figure. The AC main is plugged in and the laser light is adjusted so that it appears at
the end of the fiber on the NA jig, the intensity knob is adjusted to get maximum intensity.
The white screen with the four concentric circles (10 mm, 20 mm, 30 mm and 40 mm diameter) is held
vertically at a suitable distance to make the red spot from the emitting fiber coincides with the 10 mm circle,
the diameter (D) of the spot is noted. The distance (X) of the screen from the fiber end is recorded.
The procedure is repeated for 20 mm, 30 mm, 40 mm diameter circles and the readings are tabulated.




26

















RESULT:
The numerical aperture, NA = ----------------
Acceptance angle, ? = ----------------




27




1. What is semiconductor diode laser?
2. What is meant by active material in laser?
3. What is meant by LASER?
4. What is stimulated emission?
5. What are the characteristics of laser radiation?
6. What is homo?junction laser?
7. What is hetero?junction laser?
8. What are the applications of semiconductor laser?
9. What are the conditions required for laser action?
10. Define ? Numerical aperture







Viva ? voce
28


Lee?s disc setup


29

Expt. No. 4 THERMAL CONDUCTIVITY OF A BAD CONDUCTOR
BY LEE?S DISC METHOD

AIM:
To determine the coefficient of thermal conductivity of a bad conductor
APPARATUS REQUIRED:
Lee?s disc apparatus, bad conductors, stop-clock, thermometers, screw gauge, vernier calipers and
steam boiler
FORMULA:
Thermal conductivity of a bad conductor,
? ?
? ? ? ?
1 1
2 1
2
2 2
2
? ?
? ?
?
?
?
?
?
?
?
?
?
? k Wm
h r r
h r d
dt
d
MS
K
? ? ?
?

M ? Mass of the metallic disc (Kg)
S ? Specific heat capacity of the metallic disc ( J Kg
-1
K
-1
)
? rate of cooling at steady temperature (
o
C/s)
d ? thickness of the bad conductor (m)
h ? thickness of the metallic disc (m)
r?radius of the metallic disc (m)
1
? ? steady temperature of the steam chamber (
o
C)
2
? ? steady temperature of the Metallic disc (
o
C)

PROCEDURE:
The thickness of the bad conductor say card board and thickness of the metallic disc are determined
using a screw gauge. The radius of the metallic disc is found using a vernier caliper. The mass of a metallic
disc is also found using a common balance. The readings are tabulated.

30

To find the radius of the metallic disc (r) using Vernier Calipers
Least count = 0.01cm Zero error = ? ???div
Zero correction = ? ???cm
= --------- ?10
-2
m
Sl.No.
MSR
(x10
-2
m)
VSC
(div.)
OR = MSR +(VSC x LC)
(x10
-2
m)
CR = OR ? ZC
(x10
-2
m)
1
2
3
4

Mean radius, r = --------------------------------- x10
-2
m
To find the thickness of the bad conductor (d) using Screw gauge
Least count = 0.01mm Zero error = ? ???div
Zero correction = ? ???mm
Sl.No.
PSR
(x10
-3
m)
HSC
(div.)
OR = PSR + (HSC x LC)
(x10
-3
m)
CR = OR ? ZC
(x10
-3
m)
1.
2.
3.
4.

Mean, d = -------------------------------- x10
-3
m
31

The whole Lee?s disc apparatus is suspended from a stand as shown in the figure. The given bad
conductor is placed in between the metallic disc and the steam chamber. Two thermometers T1 and T2 are
inserted into the respective holes.
Steam from the steam boiler is passed into the steam chamber until the temperature of the steam
chamber and the metallic disc are steady. The Steady temperature (?1) of the steam chamber and (?2) of the
metallic disc recorded by the thermometers are noted.
Now the bad conductor is removed and the steam chamber is placed in direct contact with the metallic
disc. The temperature of the disc rapidly rises. When the temperature of the disc rises about 10
o
Cabove
?2
o
C, the steam chamber is carefully removed after cutting of the steam supply.
When the temperature of the disc reaches 10
o
C above the steady temperature of the disc i.e. (?2+
10)
o
C , stop clock is started. Time for every one degree celsius fall of temperature is noted until the metallic
disc attains a temperature (?2 - 10)
o
C.
A graph is drawn taking time along the x-axis and temperature along the y-axis. The cooling curve is
obtained .To obtain the rate of the cooling (
????
????
)
?? 2
from this graph, a triangle is drawn by taking 1
o
C above
and 1
o
Cbelow the steady temperature ?2. Then the slope AB / BC gives the rate of cooling at(
????
????
)
?? 2
. From
these readings and using the given formula thermal conductivity of the given bad conductor is calculated.










32

To find the thickness of the metallic disc (h) using screw gauge
Least count = 0.01mm Zero error = ? ???div
Zero correction = ? ???mm
Sl.No.
PSR
(x10
-3
m)
HSC
(div.)
TR = PSR + (HSC x LC)
(x10
-3
m)
Corrected reading
CR = TR ? ZC
(x10
-3
m)
1
2
3
4
5

Mean, h = ------------------------------ x10
-3
m
To determine the rate of cooling of metallic disc:
Time
s
Temperature
o
C
Time
s
Temperature
o
C







33

CALCULATION:
Mass of the disc, m= ---------- x10
-3
kg
Specific heat capacity of the disc,c = 385 J kg
-1
K
-1
Rate of cooling at ?2,
????
????
= -------------- deg s
-1
Radius of the disc, r = ---------- x10
-2
m
Height of the disc, h = ---------- x10
-2
m
Thickness of the bad conductor, d = ---------- x10
-3 m
Temperature of steam, ?1 = ---------
o
C
Steady temperature of the disc, ?2 = -------------
o
C
Thermal conductivity,
? ?
? ? ? ?
1 1
2 1
2
2 2
2
? ?
? ?
?
?
?
?
?
?
?
?
?
? k Wm
h r r
h r d
dt
d
MS
K
? ? ?
?


= --------------------

= -------------------- Wm
-1
K
-1








34
















RESULT:
The thermal conductivity of the given bad conductor by Lee?s disc method, K = -------------- Wm
-1
K
-1







35





1. What is meant by thermal conductivity?
2. What is meant by Rate of cooling?
3. Does the value of thermal conductivity depend on the dimension of the specimen?
4. Is there any reason to take the specimen in the form of a disc?
5. Can this method be used for good conductors?
6. What is lee's disc method?
7. What are the differences between good conductor and bad conductor?
8. What are the methods used to determine thermal conductivity of bad conductor?
9. What is meant by steady temperature?
10. What is meant by specific heat capacity?

Viva ? voce
36




37


Exp. No. 5 ULTRASONIC INTERFEROMETER

AIM:
To determine the velocity of the ultrasonic waves in a given liquid and to find the compressibility of
the liquid using ultrasonic interferometer
APPARATUS REQUIRED:
Ultrasonic interferometer (high frequency) generator, measuring cell, the experimental liquid
and coaxial cables
FORMULA:
1) Velocity of the ultrasonic waves v = f ? ms
-1
where,
f ?frequency of the ultrasonic waves (Hz)
? ? wavelength of the ultrasonic waves in the liquid (m)

2) Compressibility of the liquid ? =
1
?? 2
?? m
2
N
-1
where
? ? density of the given liquid (kg m
-3
)
v? velocity of the ultrasonic waves with in the liquid (m s
-1
)
DESCRIPTION:
The interferometer consists of (i) high frequency generator and (ii) measuring cell. The high
frequency generator is used to excite the quartz plate fixed at the bottom of the measuring cell.
The exited quartz plate generates ultrasonic waves in the experimental liquid contained in the cell. A micro
ammeter is provided to observe the change in the current.
Two control knobs are also provided in the generator for the purpose of sensitivity regulation and also
adjustment. The measuring cell is a double walled cell to maintain constant temperature during

38


To find the wavelength of the ultrasonic waves in the liquid:

Order of
maximum current

Micrometer reading
Distance for n
maximum current, d
(x10
-3
m)
Wavelength
?=2d/n
(x10
-3
m)
PSR
(x10
-3
m)
HSR
(div)
TR
(x10
-3
m)

x
x+n
x+2n
x+3n



Wavelength, ? = ------------------ x10
-3
m
Frequency of ultrasonic waves = 2 MHz

CALCULATION:
1) The Velocity of the ultrasonic waves, v = f?
= ---------- m s
-1
The density of the given liquid ? = ---------- kg m
-3
2) Adiabatic compressibility of the liquid, ? =
1
?? 2
??
= -----------
Adiabatic compressibility of the liquid, ? = --------------


39

experiment.A fine micrometer arrangement is fixed at the top of the interferometer, enables the reflector
pates to move upward or downward through a known distance.
PRINCIPLE:
The velocity of the ultrasonic waves is determined using the interferometer. The principle used in the
measurement of velocity is based on the accurate determination of the wave length (?) of ultrasonic waves
in the liquid. The ultrasonic waves are reflected back by a removable metallic plate parallel to the crystal
.These two ultrasonic waves superimpose producing stationary wave pattern within the medium.

If the separation between these two plates is exactly an integral multiple of ?/2 of the ultrasonic
waves, acoustic resonance is produced in the standing waves.

This acoustic resonance gives rise to an electrical reaction on the generator and the anode current of the
generator becomes maximum.
PROCEDURE:
The measuring cell is connected to the output terminal of the high frequency generator through a
shielded cable. The cell is filled with an experimental liquid before switching on the generator. The
ultrasonic waves move normally from the quartz crystal till they are reflected back from the movable plate
and the standing waves are formed in the liquid in between the reflector plate and the quartz crystal.
The micrometer is slowly moved till the anode current of the high frequency generator shows a
maximum in the meter. Now the initial reading of the micrometer screw is noted. If the micrometer is rotated
in the same direction, the current various between minimum and maximum.Micrometer screw is rotated in
the same direction until n
th
maximum in the micro ammeter is reached. The reading in the micrometer is
noted.
For n number of maximum anode current, the distance moved (d) is measured with the help of
micrometer. Hence
d = n?/2Therefore, ? = 2d/n
The frequency of the ultrasonic waves is noted as f (Hz)
The experiment is repeated for various n number of maximum and the readings are tabulated.
Knowing the meaning value of ?, the velocity of the ultrasonic waves is calculated.
40

If the distance is now increased or decreased and the variation is exactly one half wavelengths
(?/2) or multiple of it, anode current becomes maximum. From the knowledge of wave length (?) the velocity
v can be obtained using the following relation.
v = f ?
By substituting the value of the density of the given liquid and the velocity of the ultrasonic waves in
the given liquid, the adiabatic compressibility of the given liquid is calculated.





RESULT:
i) Wave length of the ultrasonic waves in the liquid = ---------- m
ii) Velocity of the ultrasonic waves in the liquid = --------- m s-
1
iii) Compressibility of the given liquid = --------- N
-1
m
2








41



1. What are ultrasonic waves?
2. Define Piezo ? Electric effect
3. Explain inverse Piezo ? Electric effect
4. Is ultrasonic wave,an electro-magnetic wave? Explain.
5. What is meant by acoustical grating?
6. Give the properties of ultrasonic waves.
7. What are the methods used to produce ultrasonic waves?
8. What is meant by SONAR?
9. What is meant by Compressibility?
10. What are the applications of ultrasonic waves?


Viva ? voce
42



Normal Incidence Angle of diffraction






43

Exp. No. 6 SPECTROMETER - GRATING

AIM:
To standardize the grating using sodium vapour lamp and to use it to find the wavelength of the
mercury spectra using spectrometer
APPARATUS REQUIRED:
Spectrometer grating, sodium vapour lamp and mercury vapour lamp
FORMULA:
Wavelength of the spectral line ? =
???????? ????
m
?? ? angle of diffraction (deg.)
N ? number of lines / meter length of the grating ( m
-1
)
M ? order of the spectra (No unit)
PROCEDURE:
The preliminary adjustments of the spectrometer are done.
To adjust for normal incidence:
a) The slit of the collimator is illuminated by the sodium vapour lamp. The telescope is brought in
the line with the direct ray. The tangential screw of the telescope is adjusted so that the vertical cross wire
coincides with the direct ray. The direct ray reading in the Vernier is rotated.
b) The telescope is turned through 90
?
in any direction and is fixed.
c) The grating is mounted vertically on the prism table. On viewing through the telescope, the
grating alone is rotated until the reflected image of the slit is obtained. The grating is slightly adjusted so
that the reflected image is made to coincide with the vertical cross wire. The grating is fixed at this
position.
d) Now the vernier is released and is rotated along with the grating through 45
?
in the proper
direction and is fixed. Now the grating is normal to the direct ray. This is the normal incidence position.


FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
2


PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science and fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems and use this knowledge to acquire
higher education.
2. Core competence
To train the students in Engineering Physics so as to apply their knowledge and training to compare,
and to analyze various engineering industrial problems for finding solutions.
3. Breadth
To provide relevant training and experience to bridge the gap between theoretical learning and
practice that enables them to find solutions for the real time problems in industry and to design products.
4. Professionalism
To inculcate professional and effective communication skills, leadership qualities and team spirit for
the students to make them multi-faceted personalities and develop their ability to relate engineering issues
to broader social context.
5. Lifelong learning/ethics
To demonstrate and practice ethical and professional responsibilities in the industry and society by
and large, through commitment and lifelong learning needed for successful professional career.





3


PROGRAMME OUTCOMES (POs)

a) To demonstrate and apply knowledge of Mathematics, Science and Engineering fundamentals in
Engineering physics
b) To determine the Moment of Inertia of given disc and Rigidity modulus of the given wire using
Torsional Pendulum
c) To determine Young?s modulus of a given bar using Non-Uniform bending
d) To utilize laser source and grating to estimate the wave length, particle size of given powder and
Numerical Aperture & acceptance angle of given optical fiber
e) To find the Thermal conductivity of a bad conductor using Lee?s Disc method
f) To Measure the velocity of ultrasonic wave in a liquid and compressibility of the liquid usingultrasonic
Interferometer
g) To determine the wavelength of Hg source using grating and spectrometer
h) To find the thickness of a thin wire using Air- wedge method
i) To participate and succeed in competitive exams and visualize and work on laboratory and
multidisciplinary tasks











4


BS 8161 ? PHYSICSLABORATORY
(Common to all branches of B.E. / B.TechProgrammes)
SYLLABUS


To introduce different experiments to test basic understanding of physics concepts applied in optics, thermal
physics, properties of matter and liquids.

LIST OF EXPERIMENTS: PHYSICS LABORATORY(Any 5 Experiments)
1. Determination of Rigidity modulus ? Torsion pendulum
2. Determination of Young? s modulus by Non uniform bending method
3. (a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
4. Determination of thermal conductivity of a bad conductor ? Lee?s Disc method.
5. Determination of velocity of sound and compressibility of liquid ? Ultrasonic interferometer
6. Determination of wavelength of mercury spectrum ? spectrometer grating
7. Determination of band gap of a semiconductor
8. Determination of thickness of a thin wire ? Air wedge method




Completion of the course, the students will be able to: apply physics principles of optics and thermal physics
to evaluate engineering properties of materials.


COURSE OUTCOMES
COURSE OBJECTIVES
5

BS 8161 ? PHYSICS LABORATORY
CONTENTS

Sl.No. Name of the Experiment (any 5 experiments)
Page
No.
1.
Determination of Rigidity modulus ? Torsion pendulum
6
2.
Determination of Young ?s modulus by Non uniform bending method
12
3.
(a) Determination of Wavelength, and particle size using Laser.
(b) Determination of acceptance angle in an optical fiber.
18
4.
Determination of thermal conductivity of a bad conductor ? Lee ?s Disc method.
28
5.
Determination of velocity of sound and compressibility of liquid ? Ultrasonic
interferometer
37
6.
Determination of wavelength of mercury spectrum ? spectrometer grating
42
7.
Determination of thickness of a thin wire ? Air wedge method
48
MEASURING INSTRUMENTS
M1 Screw gauge 54
M2 Vernier Calipers 58
M3 Travelling Microscope 62
M4 Spectrometer 66








6

TORSIONAL PENDULUM










7

Expt. No.1 TORSIONAL PENDULUM

AIM:
To determine the moment of inertia of the given disc and hence to determine the rigidity modulus of
the material of the given suspension wire by torsional oscillations
APPARATUS REQUIRED:
Torsional pendulum, two equal masses, stop clock, screw gauge and meter scale

FORMULA:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
where
m ?mass of the cylinder placed on the disc (kg)
To ?period of the pendulum for a length of l without mass (s)
T1?period of the pendulum for the same length when mass m is placed at a distance d 1
from the center of the suspension wire (s)
T2?period of the pendulum for the same length when mass m is placed at a distance d 2
from the center of the suspension wire (s)
a ? radius of the suspension wire (m)




8

1. To determine the time period of the disc:
Length of the wire (l)= --------
2
10
?
? m
Position of the equal
masses
Time for 10 oscillations Time period
(one oscillation)
s
Trial-1
s
Trial-2
s
Mean
s
Without any masses T0
With masses at
d1 = x10
-2
m
T1
With masses at
d2 = x10
-2
m
T2

2. To determine the radius of the wire:
Least count =0 .01 mm. Zero Error ZE = --------- divisions
Zero Correction ZC = ---------- mm

Sl.No.
Pitch Scale
Reading
PSR
3
10
?
? m
Head Scale
Coincidence
HSC
div
Observed reading
OR = PSR + (HSCXLC)
3
10
?
? m
Correct reading
CR = OR ? ZC
3
10
?
? m




Mean = ----------------
3
10
?
? m



9

PROCEDURE:
Torsional pendulum is suspended from vertical chuck. The length of the suspension wire is measured
between the vertical chuck and the chuck attached to the uniform circular disc (i). The circular disc is twisted
slightly without masses on the disc. Now it executes torsional oscillations. Care is taken to see that the disc
oscillates without wobbling. Time taken for 20 oscillations is noted with the help of a stop clock. Two trials are
taken. The average of these two trial readings is calculated from which the period of oscillations is found out
as T0.
Two identical cylindrical masses each of mass m are symmetrically placed on the disc on either side
of the wire at a distance d from the center of the disc. As before the disc is gently twisted. Time taken for 20
oscillations is noted from which the period of oscillation is calculated as T1.
The cylindrical masses are placed at a distance d2 from the center and the experiment is repeated.
The mean time period of oscillations is calculated T2.
The diameter of the specimen wire is measured accurately with the help of the screw gauge, at
various places on the wire. The average diameter and hence the radius of the wire is calculated as r.
Moment of inertia and the rigidity modulus are determined by the substituting the value of m, T 0, T1, T2,
T3, and l in the formula.










10

CALCULATION:
Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2

Mass of cylindrical mass, m = ----------- ? 10
-3
kg
Closest distance of the mass from the centre of the suspension wire, d1 = ------------ ? 10
-2
m
Farthest distance of the mass from the centre of suspension wire, d2= ------------? 10
-2
m
Period of oscillation without mass, To = ------------- s
Period of oscillation with mass at d1, T1= ------------ s
Period of oscillation with mass at d2, T2 = ------------- s

Moment of Inertia of the disc, I =
2?? (?? 2
2
??? 1
2
)?? ?? 2
?? 2
2
??? 1
2
kg m
2
= --------------- kg m
2
= --------------- kg m
2

Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
Moment of inertia, I = ------------------ kg m
2
Length of the wire, l = ------------------- ? 10
-2
m
Time of oscillation, To = ------------------ s
Radius of the wire, a = ------------------- ? 10
-3
m
Rigidity modulus of the wire, n =
8?????? ?? ?? 2
?? 4
Nm
-2
= ----------------------
Rigidity modulus, n = ------------------- Nm
-2
11









RESULT:
(i)
The moment of inertia of the given circular disc, I = --------------- kg m
2
(ii)
The rigidity modulus of the material of the given wire, n = -------------- Nm
-2




1. State Hooke?s law.
2. Define ?Rigidity modulus
3. Define ?Moment of inertia
4. What is meant by torsional oscillation?
5. What is period of oscillation?
6. What is meant by twisting couple?
7. Define ? Shearing stress
8. Define ? Shearing strain
9. What is the unit of rigidity modulus?
10. What are the applications of torsional pendulum?


Viva ? voce
12


Young?s Modulus ? Non Uniform Bending
To determine depression (y):
L.C =.001cm M = ___________
3
10
?
? kg

Sl.No

Load


3
10
?
?
k
g
Microscope reading
Mean

2
10
?
? m
Depression
y for M kg

2
10
?
? m
Loading Unloading
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
MSR

2
10
?
? m
VSC

div
TR

2
10
?
? m
1 W
2 W+50
3 W+100
4 W+150
5 W+200
6 W+250

Mean (y) = ----------
2
10
?
? m





13

Expt. No.2 YOUNG?S MODULUS BY NON ? UNIFORM BENDING
AIM:
To determine the young?s modulus of the material of the given bar, by non-uniform bending method
APPARATUS REQUIRED:
Travelling microscope, wooden bar, knife- edge, weights hanger, slotted weight, vernier calipers,
screw gauge and pin
FORMULA:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Where,
g ? acceleration due to gravity (9.8 ms
-2
)
l ? length of the bar between two knife edges (m)
b ? breadth of the bar (m)
d ? thickness of the bar (m)
y ? depressiont in the scale reading due to the change of mass M (m)
PROCEDURE:
The given wooden bar, for which young?s modulus is to be determined, is paced symmetrically on the
two knife edges. The distance between the knife edges is measured as the length of the bar (l). It is adjusted
to be, say, 60 cm. the weight hanger is suspended at the centre of the bar. A pin is held vertically at the
centre of the bar with the help of wax.
The given bar is brought to elastic mood by loading and unloading the bar with slotted weights in steps
of 50 g. This is repeated for two or three times. With the hanger as dead load W, the microscope is focused on
to the tip of the pin. The tangential screw of the microscope is adjusted so that the image of the tip of the pin
just touches the horizontal cross wire of the eyepiece. The main scale reading and the vernier scale
coincidence corresponding to this position are noted.
14

To find the breadth using vernier calipers, b:
Least count = ---------- cm Zero error = --------- div.
= ---------- ?10
-2
m Zero correction = ?ZE ?LC= --------- ?10
-2
m
Sl. No.

MSR
x 10
-2
m

VSC
div.
Observed reading
OR = MSR+(VSC ? LC)
x 10
-2
m
Correct Reading
CR = OR ? ZC
x 10
-2
m
1.

2.

3.


Mean, b = ------------------------?10
-2
m
To find the thickness using screw gauge, d:
Least count = ---------- mm Zero error = --------- div.
= ---------- ?10
-3
m Zero correction =ZE ?LC= --------- ?10
-3
m
Sl. No.

PSR
x 10
-3
m

HSC
div.
Observed reading
OR = PSR+ (HSC ? LC)
x 10
-3
m
Correct Reading
CR = OR ? ZC
x 10
-3
m
1.

2.

3.


Mean, d = ---------------------------?10
-3
m
15


The experiment is repeated by adding weights in steps of 50 g and every time the microscope is
adjusted for coincidence. The corresponding readings are noted. The experiment is repeated by unloading the
weights in steps of 50 g and the corresponding readings are tabulated. From this table, the shift in the scale
reading, say y, for a change of mass M is found out.
The breadth of the bar is measured at various points with the help of vernier calipers. Similarly the
thickness of the bar is measured by screw gauge. Substituting the values of M, y, l, d, b and g in the formula,
the young?s modulus of the material of the given bar is calculated.

















16

CALCULATION:
Young?s modulus of the material of the material of the given bar, E =
???? ?? 2
4?? ?? 3
?? Nm
-2
Acceleration due to gravity, g = 9.8 ms
-2
Length of the bar between two knife edges, l = ------------ ?10
-2
m
Breadth of the bar, b = ----------- ?10
-2
m
Thickness of the bar, d = ----------- ?10
-3
m
y = -----------?10
-2
m
E =
???? ?? 2
4?? ?? 3
?? Nm
-2

= ---------------
Young?s modulus, E = ----------- Nm
-2












17








RESULT:
Young?s modulus of the material of the given bar, E = ---------- Nm
-2


1. Define ? Young?s modulus
2. What is meant by Non-uniform bending?
3. Define ? Stress and strain
4. State Hooke?s law.
5. Define ? Neutral axis
6. What is the SI unit of young?s modulus?
7. Define ? Elastic limit
8. Define ? Elasticity
9. What are the factors affecting elasticity?
10. Define ? Elastic fatigue

Viva ? voce
18


To find the wavelength of the laser beam, ?:
Distance between the screen and the grating, D = ------------?10
-2
m
Number of lines per meter length of the grating, N = --------------- Lines per meter
Sl. No.
Order of diffraction,
(m)
Reading of the diffracted image
(?10
-2
m)
?? ?? = ?????? ?1
(
?? ?? ?? )
(deg.)
? =
?????? ?? ?? ????
m

Left side
(xi)
Right side
(xr)
Mean
(xm)










Mean, ? = ---------------- m


19

Expt. No.3(a) WAVELENGTH OF LASER LIGHT AND PARTICLE SIZE


AIM:
(i) To determine the wavelength of the given laser light.
(ii) To determine size of the given particle.
APPARATUS REQUIRED:
Diode laser, grating, screen, given micro particles, scale and screen.
FORMULAE:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
(ii) Grain size or diameter of the grain, 2d =
?????? ?? ?? m
Where
?? ?? ?angle of diffraction (deg.)
M ?order of diffraction (No unit)
N ?number of lines per metre length of the grating (m
-3
)
n ? order of diffraction (no unit)
? ? wavelength of laser light used (m)
D ? distance between the glass plate and the screen (m)
?? ?? - distance between the central bright spot and the nth fringe (m)
PROCEDURE:
TO FIND THE WAVELENGTH OF THE GIVEN LASER LIGHT:
The laser source, grating and screen are placed properly as shown in figure. The diode laser is kept
horizontally and switched on. Extreme care should be taken to avoid direct exposure of laser light on eyes.
20











21

The grating is held normal to the laser beam by adjusting the grating in such a way that the reflected
laser beam from the grating coincides with incident laser beam. Now the diffracted laser spots of various
orders can be seen on the screen, placed on the other side of the grating.

The distance of the different orders on either side of the central spot are measured as x randxi and are
tabulated.The mean value of xrandxiare calculated as xm for the m
th
order diffracted light. The distance
between the grating and the screen is measured as D. Hence, the angle of diffraction for the m
th
order,
?? ?? = ?????? ?1
(
?? ?? ?? )
The experiment is repeated for different orders and the readings are tabulated. From the table, ? for
each order is calculated. Substituting the value of ?, the corresponding order of diffraction and the number of
lines per meter length of the grating, the wavelength is calculated.

TO FIND THE SIZE OF THE GIVEN MICRO PARTICLE:

The lycopodium powder having fine micro particles of nearly same size is sprinkled on a glass plate.
This glass plate is kept between laser source and screen.
Now the particles present in the glass plate diffract laser beam from the source. By adjusting the
distance between the glass plate and the screen, a circular fringe pattern is obtained on the screen with
different orders of fingers. Now distance between the screen and the glass plate (D) is measured.
The distance of the first order and the second order fringe from the centre of spot are also measured.
Using the formula, the particle size is found out. The experiment is repeated for different D values.
22

To find the size of the particle:

CALCULATION:
(i) Wavelength of the given laser source of light, ? =
?????? ?? ?? ????
m
Number of lines per metre in the grating, N = ------------ lines per metre.
First order, m1; ?? 1
= ------------
Wavelength, ? =
?????? ?? 1
????
= ------------
Second order, m2; ?? 2
= ------------
Wavelength, ? =
?????? ?? 2
????
= ------------
Third order, m3; ?? 3
= ------------
Wavelength, ? =
?????? ?? 3
????
= ------------
Fourth order, m4; ?? 4
= ------------
Wavelength, ? =
?????? ?? 4
????
= -------------
Fifth order, m5; ?? 5
= ------------

Sl.No



Distance between
screen and glass
plate(D)
2
10
?
? m
Order of
diffraction
(n)
Distance between the
central bright spot and n
th

fringe (xn )
2
10
?
? m
Particle size
2
n
nD
d
x
?
?
m






23

Wavelength, ? =
?????? ?? 4
????
= ------------
Mean wavelength of the given laser light, ? = -------------- m
(ii) Grain size or diameter of the grain. 2d =
?????? ?? ??
Order of differaction, n = --------------
Wavelength of laser light used, ? = ------------- m
Distance between glass plate and the screen, D = ------------ m
Distance between central bright spot and the n
th
fringe,?? ?? = ------------ m
2d =
?????? ?? ??
=
= ------------ m








RESULT:
(i) Wavelength of the laser beam, ? = -------------- m
(ii) Average size of the particle = --------------- m

24


Optical fiber

To find numerical aperture, NA:

Sl. No.
Diameter of the circular patch
D(m)
Distance between the tip of the
fiber and the screen X (m)
NA =
?? (4?? 2
+?? 2
)
1
2





Mean NA =
Therefore, the acceptance angle, ? = Sin
-1
(NA) = -------------------
= -------------------


25

Expt. No.3(b) NUMERICAL APERTURE AND ACCEPTANCE ANGLE
AIM:
To measure the numerical aperture and the acceptance angle of the given fiber cable
APPARATUS REQUIRED:
Optical fiber cable with source, NA jig and in-line adaptor
FORMULA:
The numerical aperture, NA =
?? (4?? 2
+?? 2
)
1
2

Acceptance angle, ? = Sin
-1
(NA)
where,
D ? diameter of the circular patch (m)
X ? distance between the tip of the fiber and the screen (m)
PROCEDURE:
One end of the one metre fiber cable is connected to the laser light source and the other end
to the NA jig as shown in figure. The AC main is plugged in and the laser light is adjusted so that it appears at
the end of the fiber on the NA jig, the intensity knob is adjusted to get maximum intensity.
The white screen with the four concentric circles (10 mm, 20 mm, 30 mm and 40 mm diameter) is held
vertically at a suitable distance to make the red spot from the emitting fiber coincides with the 10 mm circle,
the diameter (D) of the spot is noted. The distance (X) of the screen from the fiber end is recorded.
The procedure is repeated for 20 mm, 30 mm, 40 mm diameter circles and the readings are tabulated.




26

















RESULT:
The numerical aperture, NA = ----------------
Acceptance angle, ? = ----------------




27




1. What is semiconductor diode laser?
2. What is meant by active material in laser?
3. What is meant by LASER?
4. What is stimulated emission?
5. What are the characteristics of laser radiation?
6. What is homo?junction laser?
7. What is hetero?junction laser?
8. What are the applications of semiconductor laser?
9. What are the conditions required for laser action?
10. Define ? Numerical aperture







Viva ? voce
28


Lee?s disc setup


29

Expt. No. 4 THERMAL CONDUCTIVITY OF A BAD CONDUCTOR
BY LEE?S DISC METHOD

AIM:
To determine the coefficient of thermal conductivity of a bad conductor
APPARATUS REQUIRED:
Lee?s disc apparatus, bad conductors, stop-clock, thermometers, screw gauge, vernier calipers and
steam boiler
FORMULA:
Thermal conductivity of a bad conductor,
? ?
? ? ? ?
1 1
2 1
2
2 2
2
? ?
? ?
?
?
?
?
?
?
?
?
?
? k Wm
h r r
h r d
dt
d
MS
K
? ? ?
?

M ? Mass of the metallic disc (Kg)
S ? Specific heat capacity of the metallic disc ( J Kg
-1
K
-1
)
? rate of cooling at steady temperature (
o
C/s)
d ? thickness of the bad conductor (m)
h ? thickness of the metallic disc (m)
r?radius of the metallic disc (m)
1
? ? steady temperature of the steam chamber (
o
C)
2
? ? steady temperature of the Metallic disc (
o
C)

PROCEDURE:
The thickness of the bad conductor say card board and thickness of the metallic disc are determined
using a screw gauge. The radius of the metallic disc is found using a vernier caliper. The mass of a metallic
disc is also found using a common balance. The readings are tabulated.

30

To find the radius of the metallic disc (r) using Vernier Calipers
Least count = 0.01cm Zero error = ? ???div
Zero correction = ? ???cm
= --------- ?10
-2
m
Sl.No.
MSR
(x10
-2
m)
VSC
(div.)
OR = MSR +(VSC x LC)
(x10
-2
m)
CR = OR ? ZC
(x10
-2
m)
1
2
3
4

Mean radius, r = --------------------------------- x10
-2
m
To find the thickness of the bad conductor (d) using Screw gauge
Least count = 0.01mm Zero error = ? ???div
Zero correction = ? ???mm
Sl.No.
PSR
(x10
-3
m)
HSC
(div.)
OR = PSR + (HSC x LC)
(x10
-3
m)
CR = OR ? ZC
(x10
-3
m)
1.
2.
3.
4.

Mean, d = -------------------------------- x10
-3
m
31

The whole Lee?s disc apparatus is suspended from a stand as shown in the figure. The given bad
conductor is placed in between the metallic disc and the steam chamber. Two thermometers T1 and T2 are
inserted into the respective holes.
Steam from the steam boiler is passed into the steam chamber until the temperature of the steam
chamber and the metallic disc are steady. The Steady temperature (?1) of the steam chamber and (?2) of the
metallic disc recorded by the thermometers are noted.
Now the bad conductor is removed and the steam chamber is placed in direct contact with the metallic
disc. The temperature of the disc rapidly rises. When the temperature of the disc rises about 10
o
Cabove
?2
o
C, the steam chamber is carefully removed after cutting of the steam supply.
When the temperature of the disc reaches 10
o
C above the steady temperature of the disc i.e. (?2+
10)
o
C , stop clock is started. Time for every one degree celsius fall of temperature is noted until the metallic
disc attains a temperature (?2 - 10)
o
C.
A graph is drawn taking time along the x-axis and temperature along the y-axis. The cooling curve is
obtained .To obtain the rate of the cooling (
????
????
)
?? 2
from this graph, a triangle is drawn by taking 1
o
C above
and 1
o
Cbelow the steady temperature ?2. Then the slope AB / BC gives the rate of cooling at(
????
????
)
?? 2
. From
these readings and using the given formula thermal conductivity of the given bad conductor is calculated.










32

To find the thickness of the metallic disc (h) using screw gauge
Least count = 0.01mm Zero error = ? ???div
Zero correction = ? ???mm
Sl.No.
PSR
(x10
-3
m)
HSC
(div.)
TR = PSR + (HSC x LC)
(x10
-3
m)
Corrected reading
CR = TR ? ZC
(x10
-3
m)
1
2
3
4
5

Mean, h = ------------------------------ x10
-3
m
To determine the rate of cooling of metallic disc:
Time
s
Temperature
o
C
Time
s
Temperature
o
C







33

CALCULATION:
Mass of the disc, m= ---------- x10
-3
kg
Specific heat capacity of the disc,c = 385 J kg
-1
K
-1
Rate of cooling at ?2,
????
????
= -------------- deg s
-1
Radius of the disc, r = ---------- x10
-2
m
Height of the disc, h = ---------- x10
-2
m
Thickness of the bad conductor, d = ---------- x10
-3 m
Temperature of steam, ?1 = ---------
o
C
Steady temperature of the disc, ?2 = -------------
o
C
Thermal conductivity,
? ?
? ? ? ?
1 1
2 1
2
2 2
2
? ?
? ?
?
?
?
?
?
?
?
?
?
? k Wm
h r r
h r d
dt
d
MS
K
? ? ?
?


= --------------------

= -------------------- Wm
-1
K
-1








34
















RESULT:
The thermal conductivity of the given bad conductor by Lee?s disc method, K = -------------- Wm
-1
K
-1







35





1. What is meant by thermal conductivity?
2. What is meant by Rate of cooling?
3. Does the value of thermal conductivity depend on the dimension of the specimen?
4. Is there any reason to take the specimen in the form of a disc?
5. Can this method be used for good conductors?
6. What is lee's disc method?
7. What are the differences between good conductor and bad conductor?
8. What are the methods used to determine thermal conductivity of bad conductor?
9. What is meant by steady temperature?
10. What is meant by specific heat capacity?

Viva ? voce
36




37


Exp. No. 5 ULTRASONIC INTERFEROMETER

AIM:
To determine the velocity of the ultrasonic waves in a given liquid and to find the compressibility of
the liquid using ultrasonic interferometer
APPARATUS REQUIRED:
Ultrasonic interferometer (high frequency) generator, measuring cell, the experimental liquid
and coaxial cables
FORMULA:
1) Velocity of the ultrasonic waves v = f ? ms
-1
where,
f ?frequency of the ultrasonic waves (Hz)
? ? wavelength of the ultrasonic waves in the liquid (m)

2) Compressibility of the liquid ? =
1
?? 2
?? m
2
N
-1
where
? ? density of the given liquid (kg m
-3
)
v? velocity of the ultrasonic waves with in the liquid (m s
-1
)
DESCRIPTION:
The interferometer consists of (i) high frequency generator and (ii) measuring cell. The high
frequency generator is used to excite the quartz plate fixed at the bottom of the measuring cell.
The exited quartz plate generates ultrasonic waves in the experimental liquid contained in the cell. A micro
ammeter is provided to observe the change in the current.
Two control knobs are also provided in the generator for the purpose of sensitivity regulation and also
adjustment. The measuring cell is a double walled cell to maintain constant temperature during

38


To find the wavelength of the ultrasonic waves in the liquid:

Order of
maximum current

Micrometer reading
Distance for n
maximum current, d
(x10
-3
m)
Wavelength
?=2d/n
(x10
-3
m)
PSR
(x10
-3
m)
HSR
(div)
TR
(x10
-3
m)

x
x+n
x+2n
x+3n



Wavelength, ? = ------------------ x10
-3
m
Frequency of ultrasonic waves = 2 MHz

CALCULATION:
1) The Velocity of the ultrasonic waves, v = f?
= ---------- m s
-1
The density of the given liquid ? = ---------- kg m
-3
2) Adiabatic compressibility of the liquid, ? =
1
?? 2
??
= -----------
Adiabatic compressibility of the liquid, ? = --------------


39

experiment.A fine micrometer arrangement is fixed at the top of the interferometer, enables the reflector
pates to move upward or downward through a known distance.
PRINCIPLE:
The velocity of the ultrasonic waves is determined using the interferometer. The principle used in the
measurement of velocity is based on the accurate determination of the wave length (?) of ultrasonic waves
in the liquid. The ultrasonic waves are reflected back by a removable metallic plate parallel to the crystal
.These two ultrasonic waves superimpose producing stationary wave pattern within the medium.

If the separation between these two plates is exactly an integral multiple of ?/2 of the ultrasonic
waves, acoustic resonance is produced in the standing waves.

This acoustic resonance gives rise to an electrical reaction on the generator and the anode current of the
generator becomes maximum.
PROCEDURE:
The measuring cell is connected to the output terminal of the high frequency generator through a
shielded cable. The cell is filled with an experimental liquid before switching on the generator. The
ultrasonic waves move normally from the quartz crystal till they are reflected back from the movable plate
and the standing waves are formed in the liquid in between the reflector plate and the quartz crystal.
The micrometer is slowly moved till the anode current of the high frequency generator shows a
maximum in the meter. Now the initial reading of the micrometer screw is noted. If the micrometer is rotated
in the same direction, the current various between minimum and maximum.Micrometer screw is rotated in
the same direction until n
th
maximum in the micro ammeter is reached. The reading in the micrometer is
noted.
For n number of maximum anode current, the distance moved (d) is measured with the help of
micrometer. Hence
d = n?/2Therefore, ? = 2d/n
The frequency of the ultrasonic waves is noted as f (Hz)
The experiment is repeated for various n number of maximum and the readings are tabulated.
Knowing the meaning value of ?, the velocity of the ultrasonic waves is calculated.
40

If the distance is now increased or decreased and the variation is exactly one half wavelengths
(?/2) or multiple of it, anode current becomes maximum. From the knowledge of wave length (?) the velocity
v can be obtained using the following relation.
v = f ?
By substituting the value of the density of the given liquid and the velocity of the ultrasonic waves in
the given liquid, the adiabatic compressibility of the given liquid is calculated.





RESULT:
i) Wave length of the ultrasonic waves in the liquid = ---------- m
ii) Velocity of the ultrasonic waves in the liquid = --------- m s-
1
iii) Compressibility of the given liquid = --------- N
-1
m
2








41



1. What are ultrasonic waves?
2. Define Piezo ? Electric effect
3. Explain inverse Piezo ? Electric effect
4. Is ultrasonic wave,an electro-magnetic wave? Explain.
5. What is meant by acoustical grating?
6. Give the properties of ultrasonic waves.
7. What are the methods used to produce ultrasonic waves?
8. What is meant by SONAR?
9. What is meant by Compressibility?
10. What are the applications of ultrasonic waves?


Viva ? voce
42



Normal Incidence Angle of diffraction






43

Exp. No. 6 SPECTROMETER - GRATING

AIM:
To standardize the grating using sodium vapour lamp and to use it to find the wavelength of the
mercury spectra using spectrometer
APPARATUS REQUIRED:
Spectrometer grating, sodium vapour lamp and mercury vapour lamp
FORMULA:
Wavelength of the spectral line ? =
???????? ????
m
?? ? angle of diffraction (deg.)
N ? number of lines / meter length of the grating ( m
-1
)
M ? order of the spectra (No unit)
PROCEDURE:
The preliminary adjustments of the spectrometer are done.
To adjust for normal incidence:
a) The slit of the collimator is illuminated by the sodium vapour lamp. The telescope is brought in
the line with the direct ray. The tangential screw of the telescope is adjusted so that the vertical cross wire
coincides with the direct ray. The direct ray reading in the Vernier is rotated.
b) The telescope is turned through 90
?
in any direction and is fixed.
c) The grating is mounted vertically on the prism table. On viewing through the telescope, the
grating alone is rotated until the reflected image of the slit is obtained. The grating is slightly adjusted so
that the reflected image is made to coincide with the vertical cross wire. The grating is fixed at this
position.
d) Now the vernier is released and is rotated along with the grating through 45
?
in the proper
direction and is fixed. Now the grating is normal to the direct ray. This is the normal incidence position.


44

To find the wavelength, ?:











FirstRanker.com - FirstRanker's Choice



?



DEPARTMENT OF SCIENCE AND HUMANITIES


I SEMESTER - R 2017

BS8161 ? PHYSICS LABORATORY







Name : _______________________________________
Register No : _______________________________________
Section : _______________________________________


LABORATORY MANUAL
1





College of Engineering is committed to provide highly disciplined, conscientious and
enterprising professionals conforming to global standards through value based quality education and training.

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic excellence in pursuit of Technical Education at different
levels
? To train the students to sell his brawn and brain to the highest bidder but to never put a price tag on heart
and soul













VISION
MISSION
2


PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science and fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems and use this knowledge to acquire
higher education.
2. Core competence
To train the students in Engineering Physics so as to apply their knowledge and training to compare,
and to analyze various engineering industrial problems for finding solutions.
3. Breadth
To provide relevant training and experience to bridge the gap between theoretical learning and
practice that enables them to find solutions for the real time problems in industry and to design products.
4. Professionalism
To inculcate professional and effective communication skills, leadership qualities and team spirit for
the students to make them multi-faceted personalities and develop their ability to relate engineering issues
to broader social context.
5. Lifelong learning/ethics
To demonstrate and practice ethical and professional responsibilities in the industry and society by
and large, through commitment and lifelong learning needed for successful professional career.





3


PROGRAMME OUTCOMES (POs)

a) To demonstrate and apply knowledge of Mathematics, Science and Engineering fundamentals in
Engineering physics
b) To determine the Moment of Inertia of given disc and Rigidity modulus of the given wire using
Torsiona