Second Semester - B.Tech. Degree Examination
Engineering Physics
Time: 2 hours Max.
Marks: 50
Note: All the objective questions
are compulsory (Part A)
Answer any ONE full question from
each module (Part B).
Physical constants: Velocity of
light, c = 3×108 m/s; h = 6.63×10-34Js; k = 1.38×10-23J/K;
me = 9.1×10-31Kg;
e = 1.6×10-19C.
Part
A
1. To determine the type of semiconductors, we can use
A)
Hall effect B) Thermionic
emission C) Field emission D) None of these
2.
Classical free electron theory
was developed by
A)
Drude and Lorentz B) Fermi and Dirac
C)
Bose and Einstein D) Sommerfeld
3. Which one of the
following is not a type of fiber?
A) Multimode fiber B) Graded index fiber C) Gaseous fiber D) Step-index fiber
4. Which one of the following is a gas laser?
A)
Ruby laser B) semiconductor laser C)
He-Ne laser D) Nd:YAG laser
5. Specific heat of superconductors undergoes a
discontinuous change below
A)
Room temperature B) Boiling point
C)
Zero Kelvin D)
Transition temperature
6. Two opposite poles (north pole and south pole)
separated by a distance ‘2l’ constitute a
A)
Magnetic dipole B) Magnetic moment C)
Susceptibility D) Superconductor
7. In a triclinic lattice,
A)
a=b=c B) a¹b¹c
C) a=b¹c
D)
a¹b=c
8. Minimum volume unit cell is called as
A)
Zero cell B) Primitive cell C) Quantum cell D) Nano cell
9. Which one of the following is an interference experiment?
A)
Air wedge B) Newton’s rings C)
Both A and B D) None of these
10. Which
one of the following is not an optical instrument?
A)
Grating B) Lens C) Telescope D)
Galvanometer
(10×1Mark)
Part B
Module
1
11 (a) What is Fermi energy? Discuss variation of Fermi factor
with energy and temperature. (5
Marks)
(b) The Fermi
level in the silver is 5.5 eV. Find the velocity of conduction electrons in
silver. (3Marks)
OR
12
(a) What
are free electrons? Write down the assumptions
of classical free electron theory. (5
Marks)
(b) Calculate the probability of an electron
occupying an energy level 0.01 eV above the Fermi level at 100 K in a material. (3
Marks)
Module
2
13
(a) Explain Spontaneous emission and stimulated emission. (4
Marks)
(b)
An optical fiber has a core material with refractive index 1.55, and its
cladding material has a refractive index of 1.50. The light is launched into it
in air. Calculate its numerical aperture and the acceptance angle. (4 Marks)
OR
14 (a) Derive
the expression for numerical aperture and acceptance angle of an optical fiber.
(5 Marks)
(b)
A medium in thermal equilibrium at temperature 300 K has two energy levels with
a wavelength separation of 1 μm. Find the ratio of population densities of the
upper and lower levels. (3
Marks)
Module
3
15
(a) Write a note on classification of magnetic materials. What is coercivity? (5 Marks)
(b) A magnetic
material has a magnetization of 3300 A/m and produces a flux density of 0.00471
wb/m2. Calculate magnetizing force. (3 Marks)
OR
16
(a) Explain BCS theory of superconductivity. (4
Marks)
(b) The critical
field of Niobium is 100000 A/m at 8 K and 200000 A/m at 0K. Calculate the
transition temperature of the element. (4
marks)
Module
4
17 (a) What are
primitive and non primitive cells? Explain using figures. (4 Marks)
(b) Ni has fcc structure with lattice
constant 3.52 Å. Calculate the interplanar spacings for (101), (123) and (320)
planes. (4
Marks)
OR
18
(a) Calculate the packing factor for simple cubic and face centered cubic
structures. (4 Marks)
(b)
The minimum order of Bragg’s reflection occurs at an angle 200 in
the plane [212]. Find the wavelength of X-ray if lattice constant is 3.615 Å. (4
Marks)
Module
5
19 (a) What is a zone plate?
Compare it with a convex lens. (4 Marks)
b)
What is the radius of the first half period zone in
a zone plate behaving like a convex lens of focal length 60 cm for light of
wavelength 6000Å? (4 Marks)
OR
20
(a) What is diffraction and interference? Explain the difference between
diffraction and interference bands. (4
Marks)
(b) A soap film of
refractive index 1.33 and thickness 1.5×10-4 cm is illuminated by
white light incident at an angle of 60o. The light reflected by it
is examined by a spectroscope in which is found a dark band corresponding to a
wavelength of 5×10-5 cm. Calculate the order of interference of the
dark band. (4 Marks)
Scheme of
Evaluation
Part
A
1.
A) Hall effect
2.
A) Drude and Lorentz
3.
C) Gaseous fiber
4.
C) He-Ne laser
5.
D) Transition temperature
6.
A) Magnetic dipole
7.
B) a¹b¹c
8.
B) Primitive cell
9.
C)
Both A and B
10. D) Galvanometer
Part
B
11 (a) Fermi energy – 1 Mark
Variation of Fermi factor with energy and temperature – Graph – 1
Mark Explanation – 3 Marks
(b)
EF =
⸫ vF =
= 1.39×106m/s – 1
Mark
12(a) Free electrons – 1 Mark 4 Assumptions
-4×1 Mark
(b) f(E) =
=
= 0.239 – 1 Mark
13(a)
Spontaneous
emission – 2 Marks Stimulated
emission – 2Marks
(b)
Numerical
Aperture, NA=
=
= 0.39 – 1 Mark
Acceptance
angle = sin-1(NA) – 1 Mark
= sin-1(0.39)
= 230 –
1 Mark
14
(a) Figure – 1Mark
Derivation
of acceptance angle im = sin-1
Numerical
aperture
(b)
=
= 1.364 ×
15(a)
Diamagnetic,
Paramagnetic, Ferromagnetic - 3× 1 Mark
Coercivity-2 marks
(b)
B
= µ0(H+M) – 1 Mark ⸫
Magnetising force, H =
= 450 A/m – 1 Mark
16(a) Bardeen,
Cooper and Schrieffer – 1 mark
Electron- lattice- electron
interaction and explanation – 1 Marks
Cooper
pairs and properties – 2 marks
(b) ) Hc(T) = Hc(0)
[1-
= 11.3 K – 1 Mark
17(a)
Primitive cell with figure – 2 Marks Non-Primitive
cell with figure – 2 Marks
(b)
dhkl =
For (101) planes, dhkl =
For
(123) planes, dhkl =
For
(320) planes, dhkl =
18(a)
Simple cubic – 2 Marks Face
centered cubic – 2 Marks
(b) dhkl =
2dsinθ
= n𝛌-1 Mark 𝛌 =
19(a)
Zone plate – 2 Marks
Comparison
with convex lens – 2Marks
(b)
fn =
r1
=6×10-4m – 1 Mark
20
(a) Interference – 1 Mark Diffraction
– 2 Marks
Bands
– any 2 differences - 2×1 Mark
(b) 2 µ t cos r =
nλ – 1 Mark n=
Substitution
– 1 Mark n=6
– 1Mark
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