Download JNU 2020 Physical Science (Phyh) Previous Question Paper  Jawaharlal Nehru University (JNU) Last 10 Years Question Paper
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Roll No:
Application No:
Name:
Exam Date: 05Oct2020
Exam Time: 09:0012:00
Examination: 1. Course Code  Ph.D.
2. Field of Study  Physical Science (PHYH)
SECTION 1  SECTION 1
Case Study  1 to 3 (Question Id  53)
Question No.1 (Question Id  54)
The surface bound charge b is :
(A)
(B)
(C)
(D)
kR (Correct Answer)
Question No.2 (Question Id  55)
The volume bound charge (b) is :
(A)
(B)
 3kr
(C)
 3k (Correct Answer)
(D)
Question No.3 (Question Id  56)
The electric field outside the sphere is :
(A)
4kR2
(B)
(C)
0 (Correct Answer)
(D)
Question No.4 (Question Id  7)
(A)
(Correct Answer)
(B)
(C)
(D)
Question No.5 (Question Id  14)
For an atom with an electronic configuration np2 (where n is the principal quantum number of a shell),
the possible values of total angular momentum L and total spin S in the ground state are :
(A)
L = 2 and S = 0
(B)
L = 2 and S = 1
(C)
L = 1 and S = 1 (Correct Answer)
(D)
L = 1 and S = 0
Question No.6 (Question Id  2)
(A)
(B)
(C)
(Correct Answer)
(D)
Question No.7 (Question Id  11)
Electrons are ejected from calcium surface when monochromatic light of wavelength 488 nm falls on it.
The work function of calcium is 2.28 eV. What is the maximum kinetic energy of the emitted electron ?
(Planck's constant, h = 4.14 x 1015 eV.sec; speed of light, c = 3 x 108 m/sec)
(A)
0.026 eV
(B)
26 eV
(C)
2.6 eV
(D)
0.26 eV (Correct Answer)
Question No.8 (Question Id  4)
Which one of the following is not true about the superconductors ?
(A)
TypeII superconductors realize a mixed state between the critical magnetic fields Hc1 and Hc2.
(B)
In TypeI superconductors, the penetration depth () is smaller than the coherence length ().
(C)
According to BCS theory, the copper pairs are formed due to electronphonon interaction.
(D)
Superconductivity is characterized by strongly paramagnetic behavior. (Correct Answer)
Question No.9 (Question Id  15)
(A)
(B)
(Correct Answer)
(C)
(D)
Question No.10 (Question Id  5)
Which one of the following expressions is correct for the Helmholtz free energy F(T, V, N) of a
thermodynamic system in canonical ensemble ? Here, P is pressure, V is volume, N is the number of
particles, is chemical potential, and T is temperature.
(A)
F =  PV + N (Correct Answer)
(B)
F = PV + N
(C)
F =  PV  N
(D)
F = N
Question No.11 (Question Id  1)
Let the angular momentum eigenstates with quantum number j be denoted as j, m, where m =  j,  j
+ 1, ..., j  1, j. For a system of two angular momenta j1 and j2, any state can be described as a linear
superposition of their product states j1, m1 j2, m2. For j1 = 1 and j2 = 1/2, which of the following is the
correct expression for the total angular momentum eigenstate with quantum numbers jtotal = 3/2 and
mtotal = 1/2 ?
(A)
(Correct Answer)
(B)
(C)
jtotal = 3/2, mtotal = 1/2 = 1, 01/2, 1/2
(D)
jtotal = 3/2, mtotal = 1/2 = 1, 11/2,  1/2
Case Study  12 to 14 (Question Id  33)
Consider a gas of N free electrons confined in a volume V. (m is the electron mass, is Planck's constant and kB is
Boltzmann's constant.)
Answer the following three questions on the free electron gas problem.
Question No.12 (Question Id  34)
What is the density of states for the free electrons ?
(A)
(B)
(C)
(Correct Answer)
(D)
Question No.13 (Question Id  35)
What is the Fermi energy in terms of N and V ?
(A)
(B)
(C)
(Correct Answer)
(D)
Question No.14 (Question Id  36)
How does the specific heat (CV) of free electron gas vary with temperature (T) at low temperatures ?
(A)
CV T3
(B)
(C)
CV T2
(D)
CV T (Correct Answer)
Case Study  15 to 17 (Question Id  45)
Consider the function f (z) = e1/z of a complex variable z = x + iy in a complex plane. Answer the following three
questions on this function.
Question No.15 (Question Id  46)
The function f (z) = e1/z has :
(A)
no singularity at z = 0
(B)
an essential singularity at z = 0 (Correct Answer)
(C)
a simple pole at z = 0
(D)
a branch point at z = 0
Question No.16 (Question Id  47)
(A)
(B)
i
(C)
i2 (Correct Answer)
(D)
2
Question No.17 (Question Id  48)
The equation of the contour corresponding to a fixed value, A, of the amplitude of the function e1/z is :
(A)
(Correct Answer)
(B)
(C)
(D)
Question No.18 (Question Id  19)
(A)
 cos 2q
(B)
cos 2q
(C)
1 (Correct Answer)
(D)
0
Case Study  19 to 21 (Question Id  41)
Answer the following three questions on the relativistic corrections to the hydrogen problem.
Question No.19 (Question Id  42)
The leading relativistic correction to the kinetic energy term in the hydrogen atom Hamiltonian is :
(A)
(B)
(C)
(Correct Answer)
(D)
Question No.20 (Question Id  43)
The relativistic correction to the hydrogen atom problem leading to spinorbit interaction is given by :
(A)
(B)
(Correct Answer)
(C)
(D)
Question No.21 (Question Id  44)
(A)
Only l = 0 states (Correct Answer)
(B)
Only l = 1 states
(C)
Only l = 2 states
(D)
All l states
Case Study  22 to 24 (Question Id  37)
Question No.22 (Question Id  38)
The tail current is :
(A)
5 mA
(B)
10 mA
(C)
6 mA (Correct Answer)
(D)
8 mA
Question No.23 (Question Id  39)
The value of emitter current is :
(A)
1 mA
(B)
2 mA
(C)
3 mA (Correct Answer)
(D)
4 mA
Question No.24 (Question Id  40)
The value of the collector voltage :
(A)
4 V
(B)
6 V (Correct Answer)
(C)
8 V
(D)
10 V
Question No.25 (Question Id  10)
Which one of the following elements cannot be used as dopants in Silicon to make it ntype
semiconductor ?
(A)
Arsenic
(B)
Phosphorus
(C)
Boron (Correct Answer)
(D)
Antimony
Question No.26 (Question Id  13)
Consider a particle in a state given by the wavefunction (x, y, z) = (y + iz)2. This wavefunction is an
eigenfunction of the angular momentum operator Lx with eigenvalue.
(A)
 2
(B)

(C)
+
(D)
+ 2 (Correct Answer)
Question No.27 (Question Id  20)
By doing an elastic scattering experiment with a beam of electrons of momentum p 120 MeV/c, we
can determine :
(Planck's constant, h = 6.63 x 1034 J.s; speed of light, c = 3 x 108 m/s; electron charge, e = 1.6 x 1019
C)
(A)
the size of a biomolecule
(B)
the lattice constants of a crystal of gold
(C)
the size of an atomic nucleus (Correct Answer)
(D)
none of the above
Case Study  28 to 30 (Question Id  21)
A "twolevel" atom is considered to have only two energy levels with energies 0 and . For a system of N non
interacting twolevel atoms with total energy E, answer the following three questions.
Question No.28 (Question Id  22)
What is the number of microstates (N, E) ?
(A)
(B)
(Correct Answer)
(C)
(D)
Question No.29 (Question Id  23)
What is the entropy per particle in the limit of large N ?
(A)
(B)
(C)
(Correct Answer)
(D)
Question No.30 (Question Id  24)
What is the corresponding temperature T ?
(A)
(Correct Answer)
(B)
(C)
(D)
Question No.31 (Question Id  8)
The decay n p + e of a neutron (n) into a proton (p) and an electron (e) is forbidden due to the
violation of conservation of :
(A)
Angular momentum and baryon number
(B)
Energy and lepton number
(C)
Angular momentum and lepton number (Correct Answer)
(D)
Electric charge and baryon number
Case Study  32 to 34 (Question Id  49)
Consider a crystalline material which, under ambient conditions, is given to have the FCC (facecentered cubic) lattice
structure with monoatomic basis. Answer the following three questions for this system.
Question No.32 (Question Id  50)
A primitive unit cell of the monoatomic FCC crystal contains :
(A)
1 atom (Correct Answer)
(B)
2 atoms
(C)
3 atoms
(D)
4 atoms
Question No.33 (Question Id  51)
The phonon dispersion of a monoatomic FCC crystal has :
(A)
3 branches of acoustic phonons only. (Correct Answer)
(B)
3 branches of acoustic phonons, and 9 branches of optical phonons.
(C)
1 branch of acoustic phonons, and 2 branches of optical phonons.
(D)
3 branches of optical phonons only.
Question No.34 (Question Id  52)
Suppose by changing the temperature, if the crystal structure of the material changes from the
monoatomic FCC to monoatomic BCC (bodycentered cubic), then the number of optical phonon
branches will change by :
(A)
0 (Correct Answer)
(B)
2
(C)
3
(D)
6
Case Study  35 to 37 (Question Id  57)
Answer the following three questions on the semiempirical formula for the binding energy of atomic nuclei in terms of
the nuclear mass number A and the proton number Z.
Question No.35 (Question Id  58)
In the formula for binding energy per nucleon, the volume energy term is :
(A)
a constant (Correct Answer)
(B)
proportional to Z
(C)
proportional to A
(D)
proportional to A1/3
Question No.36 (Question Id  59)
In the formula for binding energy per nucleon, the contribution from Coulomb repulsion between protons
is :
(A)
proportional to Z only
(B)
proportional to Z(Z1) only
(C)
proportional to Z(Z  1)A1/3
(D)
proportional to Z(Z  1)A4/3 (Correct Answer)
Question No.37 (Question Id  60)
In the formula for binding energy per nucleon, the pairing energy term is :
(A)
always zero
(B)
zero only when A is an odd integer (Correct Answer)
(C)
nonzero only when A is an odd integer
(D)
always nonzero
Question No.38 (Question Id  3)
(A)
0
(B)
(Correct Answer)
(C)
(D)
Case Study  39 to 41 (Question Id  29)
A body of mass m is thrown up vertically with an initial speed u. The air exerts a drag force  kv upon it, where v is
the instantaneous velocity of the body and k is a constant. The body also experiences gravitational acceleration g.
Answer the following three questions on this problem.
Question No.39 (Question Id  30)
What is the terminal speed attained by the body ?
(A)
(Correct Answer)
(B)
(C)
(D)
u
Question No.40 (Question Id  31)
What is the time it will take to attain the maximum height ?
(A)
(B)
(C)
(Correct Answer)
(D)
Question No.41 (Question Id  32)
What is the maximum height attained by the body ?
(A)
(B)
(Correct Answer)
(C)
(D)
Question No.42 (Question Id  16)
(A)
(x + y)
(B)
(x  y)
(C)
2(x + y) (Correct Answer)
(D)
2(x  y)
Question No.43 (Question Id  17)
In spectroscopy, the selection rule for transition between the rotational energy levels of a diatomic
molecule (given by the rotational quantum number J) states that the transition between two rotational
levels is allowed if :
(A)
J = ?1 (Correct Answer)
(B)
J = ?2
(C)
J = 0
(D)
None of the above
Question No.44 (Question Id  9)
For a classical system described by the Hamiltonian H(q, p) in terms of the generalized coordinates q
and p, the Hamilton's equations of motion (in the standard notation) are :
(A)
(B)
(C)
(Correct Answer)
(D)
Question No.45 (Question Id  6)
For a thermodynamic system of N particles at temperature T, which of the following relation is correct
for the change in entropy S with respect to volume V ?
(A)
(B)
(Correct Answer)
(C)
(D)
Question No.46 (Question Id  12)
A spin1/2 particle in a magnetic field B pointing along ydirection is described by the Hamiltonian H =
BBy, where y is the Pauli matrix corresponding to the y component of the spin1/2 operator (and B
is the Bohr magneton) . For this system, the time evolution operator eiHt/ can be written as :
(A)
(B)
(C)
(D)
(Correct Answer)
Case Study  47 to 49 (Question Id  25)
Question No.47 (Question Id  26)
The commutator [aa, aa] is equal to :
(A)
 2aa
(B)
2aa
(C)
2aa (Correct Answer)
(D)
 2aa
Question No.48 (Question Id  27)
(A)
(B)
(Correct Answer)
(C)
0
(D)
Question No.49 (Question Id  28)
Which of the following is the correct expression for the creation operator ?
(A)
(B)
(Correct Answer)
(C)
(D)
Question No.50 (Question Id  18)
Consider a rectangular waveguide with a crosssection of dimension 2 cm x 1 cm. If the driving
frequency is 1.7 x 1010 Hz, the Transverse Electric (TE) mode that will propagate in this wave guide is :
(A)
0.53 x 1010 Hz
(B)
0.75 x 1010 Hz (Correct Answer)
(C)
1.9 x 1010 Hz
(D)
1.4 x 109 Hz
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This post was last modified on 21 January 2021