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Posted By: kishore Member Level: Gold Posted Date: 06 Jun 2008
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2007 Jawaharlal Nehru Technological University B.Tech Electrical and Electronics Engineering APPLIED PHYSICS setno2 Question paper
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1. (a) Define crystal lattice, unit cell, lattice parameter and coordination number.[8]
(b) Consider a body centered cubic lattice of identical atoms having radius R.
Compute
i. the number of atoms per unit cell
ii. the coordination number and
iii. the packing fraction. [8]
2. (a) What are Miller indices? Draw (111) and (110) planes in a cubic lattice. [6]
(b) Explain Bragg’s law of X-ray diffraction. [6]
(c) The Bragg’s angle for reflection from the (111) plane in a FCC crystal is 19.2o
for an X-ray wavelength of 1.54 A.U. Compute the cube edge of the unit cell.
[4]
3. (a) Explain Schottky and Frenkel defects with the help of suitable figures. [10]
(b) Explain the significance of Burgers vector. [6]
4. (a) How does the electrical resistance of a metal change with temperature? [4]
(b) Discuss the motion of an electron in a periodic lattice. [8]
(c) Find the relaxation time of conduction electrons in a metal having resistivity
1.54 × 10-8
-m, if the metal has 5.8 × 1028 conduction electrons per cubic
meter. [4]
5. (a) Obtain a relation between electronic polarization and electric susceptibility of
the dielectric medium. [6]
(b) What is dielectric breakdown? Explain briefly the various factors contributing
to breakdown in dielectrics. [6]
(c) A parallel plate capacitor having a plate separation of 2 × 10-3 m across which
a potential of 10 V is applied. Calculate the dielectric displacement, when a
material of dielectric constant 6.0 is introduced between the plates. [4]
6. (a) Explain Meissner effect. [6]
(b) What is meant by isotopic effect? Explain with suitable example. [6]
(c) A superconducting material has a critical temperature of 3.7 K, and a magnetic
field of 0.0306 tesla at 0 K. Find the critical field at 2 K. [4]
7. (a) Explain the terms:
i. Absorption.
ii. Spontaneous emission.
iii. Stimulated emission.
iv. Pumping mechanism.
v. Population inversion.
vi. Optical cavity. [12]
(b) Mention the medical applications of lasers. [4]
8. (a) Explain the principle behind the functioning of an optical fibre. [4]
(b) Derive an expression for acceptance angle for an optical fibre. How it is related
to numerical aperture? [8]
(c) An optical fibre has a numerical aperture of 0.20 and a cladding refractive
index of 1.59. Find the acceptance angle for the fibre in water which has a
refractive index of 1.33. [4]
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