Download SGBAU BSc 2019 Summer 6th Sem Physics Statistical Mechanics n Solid State Physics Question Paper

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B.Sc. (Part-III) Semester-VI Examination

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6S-PHYSICS

(Statistical Mechanics and Solid State Physics)

Time : Three Hours] [Maximum Marks : 80

Note :— Attempt all questions.

1. (A) Fill in the blanks : 2
   1. The phase space of N particles have dimensions.

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   2. Quantum statistics is applicable to identical and particles.
   3. Schottky defects are defects.
   4. Superconductors are perfectly
   (B) Choose correct alternative of the following : 2
   1. Pauli's exclusion principle is applicable to :
      1. M-B statistics
      2. B-E statistics

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      3. F-D statistics
      4. None of these
   2. Structure of NaCl crystal is :
      1. BCC
      2. FCC

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      3. Simple cubic
      4. Hexagonal
   3. For diamagnetic materials, magnetic susceptibility is :
      1. small and negative
      2. small and positive

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      3. large and negative
      4. large and positive
   4. Nanometer is equal to :
      1. 10^-6m
      2. 10^-7m

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      3. 10^-8m
      4. 10^-9m
   (C) Answer the following in one sentence : 4
   1. What are Bosons ?
   2. What is point defect ?

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   3. What is Curie temperature ?
   4. On what factors properties of nanomaterial depend ?
2. (A) Write expression for thermodynamic probability in M-B distribution and find expression for M-B distribution law. : 6
   (B) By using M-B distribution law of molecular speed show that root mean square speed of gas molecule is given by V_rms. 4
   

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   (C) Find the thermodynamic probability for four distinguishable particles for the microstate (2, 2). 2
   OR
3. (P) State and explain principle of priori probability. 4
   (Q) Show that most probable velocity of gas molecule is V_p. 4
   (R) Explain the terms :
   1. Thermodynamic probability

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   2. Statistical weight.
   4
4. (A) What are the main postulates of Fermi-Dirac statistics ? 4
   (B) Using Bose-Einstein distribution law, deduce an expression for Planck's law of energy distribution in black body radiation. 7
   (C) What is Fermi energy ? 1
   

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   OR
5. (P) Explain the concept of distinguishable and indistinguishable particles. 3
   (Q) Obtain an expression for Fermi-Dirac distribution law by assuming thermodynamic probability. 5
   (R) What is Fermi function ? How it behaves at absolute zero ? 4
6. (A) Define unit cell of crystal. Explain primitive and non-primitive unit cell. 4
   

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   (B) Derive Bragg's law for diffraction of X-rays. 4
   (C) What is line defect in crystal ? Explain the screw dislocation in crystal with neat diagram. 4
   OR
7. (P) Give the names of seven crystal systems and state the parameters of their unit cells. 6
   (Q) What are Miller indices ? Find Miller indices of the plane having intercepts (a, 2b, c/2). 4
   

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   (R) What is reciprocal lattice ? 2
8. (A) Obtain an expression for electrical conductivity in terms of mean free path of electrons. 4
   (B) Discuss formation of insulator, semiconductor and conductor on the basis of band theory of solid. 6
   (C) What are conduction electrons ? 2
   OR

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9. (P) Explain the motion of electron in metals and hence derive an expression for drift velocity of electron. 5
   (Q) Explain qualitatively conduction band, valence band and energy gap in solids. 4
   (R) Explain nearly free electron model. 3
10. (A) State properties of paramagnetic materials. 4
    (B) Explain ferromagnetism on the basis of domain theory. 4
    

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    (C) What is magnetic dipole moment ? Obtain an expression for orbital magnetic dipole moment. 4
    OR
11. (P) Give Langevin's theory of paramagnetism; hence prove that the susceptibility of paramagnetic material is inversely proportional to absolute temperature. 8
    (Q) State properties of diamagnetic material. 4
12. (A) Give brief idea of BCS theory of superconductivity. 6
    

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    (B) Explain type-I and type-II superconductor. 4
    (C) Define:
    1. Critical temperature
    2. Critical magnetic field.
    OR
13. (P) Explain importance of surface to volume ratio and quantum size effect in nanomaterials. 6
    

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    (Q) State any four applications of nanomaterials. 4
    (R) What are nanomaterials ? 2

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