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Delhi University Entrance Test (DUET) 2020 Previous Year Question Paper With Answer Key

DU MSc Physics
Topic: PHY MSC S2
1) An atomic transition line with wavelength 350 nm is observed to be split into three components in a spectrum of light
from a sunspot. Adjacent components are separated by 1.7 pm. Determine the strength of the magnetic field in the
sunspot
[Question ID = 6662]
1. 3 T [Option ID = 26642]
2. 0.03 T [Option ID = 26643]
3. 3.3 T [Option ID = 26644]
4. 0.3 T [Option ID = 26645]
Correct Answer :
0.3 T [Option ID = 26645]
2) which one of the following is correct in respect of an electron and a proton having a same deBroglie wavelength of 2 ?
[Question ID = 6663]
1. Both have same kinetic energy [Option ID = 26646]
2. Both have same velocity [Option ID = 26647]
3. Both have same momentum [Option ID = 26648]
4. The kinetic energy of proton is more than that of electron [Option ID = 26649]
Correct Answer :
Both have same momentum [Option ID = 26648]
3) If r
th
p & r are the radius and
H
Ep & E
H are the energy of an electron in the n
orbit of positronium atom and hydrogen
atom respectively, then
[Question ID = 6664]
1. rp = 2 r and E
H
p = EH/2
[Option ID = 26650]
2. rp = 2 r and E
H
p = 2 EH
[Option ID = 26651]
3. rp = 2 r and E
H
p = EH/4
[Option ID = 26652]
4. rp = rH and Ep = 2 EH
[Option ID = 26653]
Correct Answer :
rp = 2 r and E
H
p = EH/2
[Option ID = 26650]
4) An Xray beam of wavelength 0.16 nm is incident on a set of planes of a certain crystal. The first Bragg reflection is
observed for an incidence angle of 30?. What is the corresponding inter planar spacing?
[Question ID = 6669]
1. 0.16 nm [Option ID = 26670]
2. 0.67 nm [Option ID = 26671]
3. 1.02 nm [Option ID = 26672]
4. 0.89 nm [Option ID = 26673]
Correct Answer :
0.16 nm [Option ID = 26670]
5) What is the velocity of conduction electron of silver having Fermi energy 5.52 eV
[Question ID = 6670]
1. 1.39 ? 10 m/s
6
[Option ID = 26674]
2. 2.39 x 10 m/s
6
[Option ID = 26675]
3. 0.89 ? 10 m/s
6
[Option ID = 26676]
4. 0 [Option ID = 26677]
Correct Answer :
1.39 ? 10 m/s
6
[Option ID = 26674]
6) Given that a piece of ntype silicon contains 8 ? 10 m
21
phosphorus impurity atoms, calculate the carrier concentration
-3
of silicon at room temperature. Given that the intrinsic electron concentration of silicon at room temperature is 1.6 ? 1016
m-3

---

[Question ID = 6671]
1. 3.2 x 1010 m
3 [Option ID = 26678]
2. 2.3 x 1011 m
3 [Option ID = 26679]
3. 1.5 x 1010 m
3 [Option ID = 26680]
4. 3.2 x 1011 m
3 [Option ID = 26681]
Correct Answer :
3.2 x 1010 m
3 [Option ID = 26678]
7) The dispersion relation for a onedimensional monoatomic lattice chain is given by the equation,
,
where, `a' is the interatomic spacing,
and has the dimension of velocity. The relation between the phase
velocity V and group velocity V
P

g in the long wavelength limit is given by
[Question ID = 6674]
1. VP = V
g
[Option ID = 26690]
2. VP = 2V
g
[Option ID = 26691]
3. VP = V
/2
g
[Option ID = 26692]
4. Vp Vg
[Option ID = 26693]
Correct Answer :
VP = V
g
[Option ID = 26690]
8) The largest wavelength of light falling on double slits separated by 1.5 m, for which there is a first order maximum is in
the,
[Question ID = 6676]
1. ultraviolet range [Option ID = 26698]
2. visible range [Option ID = 26699]
3. infrared range [Option ID = 26700]
4. Xray range [Option ID = 26701]
Correct Answer :
infrared range [Option ID = 26700]
9) In a multistage RC coupled amplifier, the coupling capacitor
[Question ID = 6680]
1. limits the low frequency response [Option ID = 26714]
2. limits the high frequency response [Option ID = 26715]
3. reduces the amplitude of input signal [Option ID = 26716]
4. blocks d.c. component without affecting the frequency response [Option ID = 26717]
Correct Answer :
blocks d.c. component without affecting the frequency response [Option ID = 26717]
10) An AM transmitter is coupled to an aerial. The input current is found to be 5 A. With modulation the current value
increases to 5.9 A. The depth of modulation is
[Question ID = 6681]
1. 83.4% [Option ID = 26718]
2. 88.6% [Option ID = 26719]
3. 78.2% [Option ID = 26720]
4. 74.3% [Option ID = 26721]
Correct Answer :
88.6% [Option ID = 26719]
11) Hexadecimal equivalent of a digital number 10011101 is
[Question ID = 6683]
1. H913 [Option ID = 26726]
2. 9D [Option ID = 26727]
3. AE [Option ID = 26728]
4. 157 [Option ID = 26729]
Correct Answer :
9D [Option ID = 26727]
12) If the doping concentration in a SiZener diode is increased, the Zener breakdown voltage
[Question ID = 6684]

---

1. Decreases [Option ID = 26730]
2. Increases [Option ID = 26731]
3. Remains unchanged [Option ID = 26732]
4. Becomes broader [Option ID = 26733]
Correct Answer :
Decreases [Option ID = 26730]
13) Which one of the following is an example of doubly magic nuclei
[Question ID = 6685]
1.
O
18
[Option ID = 26734]
2.
Ca
48
[Option ID = 26735]
3. 124Sn
[Option ID = 26736]
4. 204Pb
[Option ID = 26737]
Correct Answer :
Ca
48
[Option ID = 26735]
14) Which radiation has maximum ionization power?
[Question ID = 6686]
1. Alpha [Option ID = 26738]
2. Beta [Option ID = 26739]
3. Neutron [Option ID = 26740]
4. Gamma [Option ID = 26741]
Correct Answer :
Alpha [Option ID = 26738]
15) For betaminus decay, which statement is TRUE?
[Question ID = 6688]
1. Daughter nuclide atomic mass (A ) is more than that of the parent nuclide atomic mass (A
D
p) [Option ID = 26746]
2. Daughter nuclide atomic number (Z ) is same that of the parent nuclide atomic number (Z
D
p) [Option ID = 26747]
3. Daughter nuclide neutron number (N ) is less than that of the parent nuclide neutron number (N
D
p) [Option ID = 26748]
4. Daughter nuclide neutron number (N ) is same that of the parent nuclide neutron number(N
D
p) [Option ID = 26749]
Correct Answer :
Daughter nuclide neutron number (N ) is less than that of the parent nuclide neutron number (N
D
p) [Option ID = 26748]
16) The probability that student A solves the problem is 1/2, and that of B is 2/3. What is the probability that the problem
is solved?
[Question ID = 6689]
1. 4/6
[Option ID = 26750]
2. 1/3
[Option ID = 26751]
3. 5/6
[Option ID = 26752]
4. none of these
[Option ID = 26753]
Correct Answer :
5/6
[Option ID = 26752]
17) Are the three points whose position vectors are 2i+3j4k, i2j+3k and 7j+10k collinear?
[Question ID = 6690]
1. Yes
[Option ID = 26754]
2. No

---

[Option ID = 26755]
3. Cannot be determined
[Option ID = 26756]
4. None of these
[Option ID = 26757]
Correct Answer :
Yes
[Option ID = 26754]
18) The number of independent fundamental solutions in nth order ordinary differential equation is
[Question ID = 6692]
1. n1 [Option ID = 26762]
2. n [Option ID = 26763]
3. n+1 [Option ID = 26764]
4. 2n [Option ID = 26765]
Correct Answer :
n [Option ID = 26763]
19) If
and
then find
[Question ID = 6693]
1. 5/266i/13
[Option ID = 26766]
2. 5/26+6i/13
[Option ID = 26767]
3. 8+18i
[Option ID = 26768]
4. 818i
[Option ID = 26769]
Correct Answer :
5/266i/13
[Option ID = 26766]
20)
The rank of the following matrix
is
[Question ID = 6699]
1. 1
[Option ID = 26790]
2. 2
[Option ID = 26791]
3. 3
[Option ID = 26792]
4. 4
[Option ID = 26793]
Correct Answer :
2
[Option ID = 26791]
21) Two Carnot engines X and Y are operating in series. The engine X receives heat at 1200 K and rejects to a reservoir at
a temperature T. The second engine Y receives the heat rejected by X and in turn rejects to a heat reservoir at 300 K.
Calculate the temperature T (in Kelvin) for the situation when the efficiency of the engines is same
[Question ID = 6704]
1. 600 K [Option ID = 26810]
2. 750 K [Option ID = 26811]
3. 0 [Option ID = 26812]
4. 450 K [Option ID = 26813]
Correct Answer :
600 K [Option ID = 26810]
22) A square conducting loop of mass m, side l and resistance R is dropped into a region with a uniform horizontal magnetic

---

field B whose direction is perpendicular to the plane of the falling loop. The loop will reach a terminal velocity given by
[Question ID = 7330]
1.
[Option ID = 29314]
2.
[Option ID = 29315]
3.
[Option ID = 29316]
4. None of these
[Option ID = 29317]
Correct Answer :
[Option ID = 29314]
23) An ideal inductor, a resistor of resistance R Ohms and a capacitor with adjustable capacitance are connected in series
to an alternating voltage with an effective value of V Volts and with frequency of f Hz. The current flowing through the
circuit when the capacitance of the capacitor is set to C is the same as when the capacitance of the capacitor is set to
1
C ,
2
. The inductance of the inductor L is given by
[Question ID = 7331]
1.
[Option ID = 29318]
2.
[Option ID = 29319]
3.
[Option ID = 29320]
4.
[Option ID = 29321]
Correct Answer :
[Option ID = 29318]
24) A cylinder of length L is made up of an inner core of steel of radius r1 and an outer sheath of copper of thickness r .
1
The resistivities of steel and copper are
and
respectively. The total resistance of the cylinder is
[Question ID = 7332]
1.
[Option ID = 29322]
2.
[Option ID = 29323]
3.
[Option ID = 29324]
4. Cannot be determined from the information provided above

---

[Option ID = 29325]
Correct Answer :
[Option ID = 29322]
25) A meter stick is at an angle of 45? to the x' axis in its rest frame. The rod moves with a speed of
along the
direction w.r.t. a frame S. The length of the rod in S is
[Question ID = 7333]
1.
[Option ID = 29326]
2.
[Option ID = 29327]
3.
[Option ID = 29328]
4.
[Option ID = 29329]
Correct Answer :
[Option ID = 29326]
26) An AC generator with output and frequency f is connected to the plates of an air filled parallel plate capacitor of plate
area A and plate separation d. The maximum value of the displacement current is
[Question ID = 7334]
1.
[Option ID = 29330]
2.
[Option ID = 29331]
3.
[Option ID = 29332]
4. Cannot be determined from the information provided
[Option ID = 29333]
Correct Answer :
[Option ID = 29330]
27) An electron enters a uniform magnetic field of flux density 1.2 Wb/m . Find the energy difference in (eV), between
2
electrons having spins parallel and antiparallel to the field. (Given:
J/T)
[Question ID = 7335]
1. 3 .95 x 10 eV
5
[Option ID = 29334]
2. 13.95 x 10 eV
5

---

[Option ID = 29335]
3. 23.95 x 10 eV
5
[Option ID = 29336]
4. 33.95 x 10 eV
5
[Option ID = 29337]
Correct Answer :
13.95 x 10 eV
5
[Option ID = 29335]
28) Using the vector atom model, determine the possible values of the angular momentum of an electron in f shell
[Question ID = 7336]
1.
[Option ID = 29338]
2.
[Option ID = 29339]
3.
[Option ID = 29340]
4.
[Option ID = 29341]
Correct Answer :
[Option ID = 29338]
29) The two eigenvalues of the matrix
are
[Question ID = 7337]
1. 2,0
[Option ID = 29342]
2. 1,1
[Option ID = 29343]
3. 1,2
[Option ID = 29344]
4. 0,1
[Option ID = 29345]
Correct Answer :
2,0
[Option ID = 29342]
30) The commutator,
, is equal to
[Question ID = 7338]
1. ihx
[Option ID = 29346]
2. 2ihx
[Option ID = 29347]
3. 2ihpx
[Option ID = 29348]
4. Zero
[Option ID = 29349]
Correct Answer :
ihx
[Option ID = 29346]
31)

---

[Question ID = 7339]
1.
[Option ID = 29350]
2.
[Option ID = 29351]
3.
[Option ID = 29352]
4.
[Option ID = 29353]
Correct Answer :
[Option ID = 29350]
32)
[Question ID = 7340]
1. 0.96 [Option ID = 29354]
2. 0.32 [Option ID = 29355]
3. 0 [Option ID = 29356]
4. 0.75 [Option ID = 29357]
Correct Answer :
0.96 [Option ID = 29354]
33) The primitive translation vector of a twodimensional lattice are
,
. The primitive translation vector of
its reciprocal lattice in xdirection is given by
[Question ID = 7341]
1.
[Option ID = 29358]
2.
[Option ID = 29359]
3.
[Option ID = 29360]
4.
[Option ID = 29361]
Correct Answer :
[Option ID = 29358]
34) The mean drift speed
of an electron in an applied electric field E with electron density `n' can be expressed as
[Question ID = 7342]
1.
[Option ID = 29362]
2.

---

[Option ID = 29363]
3.
[Option ID = 29364]
4. none of these
[Option ID = 29365]
Correct Answer :
[Option ID = 29362]
35) An undamped oscillator has time period
sec. Now a little damping is added so that its time period changes to
sec. By what factor will the amplitude of oscillation decrease after 10 cycles?
[Question ID = 7343]
1.
[Option ID = 29366]
2.
[Option ID = 29367]
3.
[Option ID = 29368]
4. None of these
[Option ID = 29369]
Correct Answer :
[Option ID = 29366]
36) A kilogram of water has a constant heat capacity of 4.2 kJ/K/kg over the temperature range 0 C to 100
?
C. The water
?
was initially at 0? C and is brought into contact with a heat reservoir at 100? C. When the water is in thermal equilibrium
with the heat reservoir calculate the change in entropy of the universe (Water + Reservoir).
[Question ID = 7344]
1.
J/K
[Option ID = 29370]
2.
J/K
[Option ID = 29371]
3.
J/K
[Option ID = 29372]
4. 1310.8 J/K
[Option ID = 29373]
Correct Answer :
J/K
[Option ID = 29370]
37) Two identical finite bodies of constant volume and of constant heat capacity at constant volume C , are used to drive a
v
heat engine. Their initial temperatures are T and
1
T . The maximum amount of work which can be obtained from the
2
system is
[Question ID = 7345]
1.
[Option ID = 29374]
2.
[Option ID = 29375]
3.
[Option ID = 29376]
4. 0
[Option ID = 29377]

---

Correct Answer :
[Option ID = 29374]
38) For a system of bosons, we can write the BoseEinstein distribution function as
, Where,

and
(kB = Boltzmann constant). If represents the chemical potential, then which one of the following is true?
[Question ID = 7346]
1.
[Option ID = 29378]
2.
[Option ID = 29379]
3.
[Option ID = 29380]
4.
[Option ID = 29381]
Correct Answer :
[Option ID = 29379]
39) An ideal capacitor C is charged to a voltage Vo and connected at t = 0 across an ideal inductor L (The circuit now
consists of a capacitor and an inductor only). If the resonant frequency
, the voltage across the capacitor at time t > 0 is given by
[Question ID = 7347]
1. V
o [Option ID = 29382]
2. V cos(
o
t)
o
[Option ID = 29383]
3. V sin(
o
t)
o
[Option ID = 29384]
4.
[Option ID = 29385]
Correct Answer :
V cos(
o
t)
o
[Option ID = 29383]
40) Magnetic moment of proton
in terms of nuclear magneton
is
[Question ID = 7348]
1.
[Option ID = 29386]
2.
[Option ID = 29387]
3.
[Option ID = 29388]
4.
[Option ID = 29389]
Correct Answer :
[Option ID = 29387]
41) Find the eigenvalues of A+4I where I is identity matrix and A =
[Question ID = 7349]
1. 1,3
[Option ID = 29390]
2. 5,7

---

[Option ID = 29391]
3. 4,4
[Option ID = 29392]
4. None of these
[Option ID = 29393]
Correct Answer :
5,7
[Option ID = 29391]
42) The limit
is
[Question ID = 7350]
1.
[Option ID = 29394]
2. 1
[Option ID = 29395]
3. 0
[Option ID = 29396]
4.
[Option ID = 29397]
Correct Answer :
1
[Option ID = 29395]
43)
is equal to
[Question ID = 7351]
1.
[Option ID = 29398]
2.
[Option ID = 29399]
3.
[Option ID = 29400]
4.
[Option ID = 29401]
Correct Answer :
[Option ID = 29398]
44)
is equal to
[Question ID = 7352]
1.
[Option ID = 29402]
2.

---

[Option ID = 29403]
3.
[Option ID = 29404]
4.
[Option ID = 29405]
Correct Answer :
[Option ID = 29403]
45) Two students are working on a math problem. The first student has probability ? of solving it and the second student
has probability ? of solving it. What is the probability that at least one of them solves the problem?
[Question ID = 7353]
1.
[Option ID = 29406]
2.
[Option ID = 29407]
3.
[Option ID = 29408]
4.
[Option ID = 29409]
Correct Answer :
[Option ID = 29408]
46) Expansion of the function
in the region defined by
is
[Question ID = 7354]
1.
[Option ID = 29410]
2.
[Option ID = 29411]
3.
[Option ID = 29412]
4.
[Option ID = 29413]
Correct Answer :
[Option ID = 29411]
47) The Fourier transformation of the function
is
[Question ID = 7355]
1.

---

[Option ID = 29414]
2.
[Option ID = 29415]
3.
[Option ID = 29416]
4.
[Option ID = 29417]
Correct Answer :
[Option ID = 29414]
48) The Laplace transformation of the function
is
[Question ID = 7356]
1.
[Option ID = 29418]
2.
[Option ID = 29419]
3.
[Option ID = 29420]
4.
[Option ID = 29421]
Correct Answer :
[Option ID = 29419]
49) Consider a collection of noninteracting particles, each of mass m in a volume where the gravitational force is a ?ve (z
direction). Consider the system is in thermal equilibrium at a temperature T. Find the partition function
[Question ID = 7357]
1.
[Option ID = 29422]
2.
[Option ID = 29423]
3.
[Option ID = 29424]
4.
[Option ID = 29425]

---

Correct Answer :
[Option ID = 29422]
50) The quantum distribution function for any gas atom which follows MB, BE and FD statistics is given as a generalized
single form
If the distribution function follows the MB statistics in a classical limit then what will be the condition of the following.
Symbols have their usual meanings
[Question ID = 7358]
1.
[Option ID = 29426]
2.
[Option ID = 29427]
3.
[Option ID = 29428]
4.
[Option ID = 29429]
Correct Answer :
[Option ID = 29427]

---