I B.Tech - Regular Examinations, June 2009
First Year
APPLIED PHYSICS - SET NO: 4
(Regulation 2007)
Time : 3 hours |
Maximam Marks:80 |
Answer any FIVE Questions
1. (a) Plot and explain the variation of (i) attractive potential energy (ii) repulsive
potential energy and (iii) resultant potential energy with inter-atomic distance,
when two atoms are brought nearer.
(b) The Madelung constant of KCl is 1.75. Its neighbour separation is 0.314 nm.
Find the cohesive energy per atom. [Given that the Repulsive exponent value
= 5.77; Ionization energy of potassium = 4.1 eV; Electron affinity of chlorine
= 3.6 eV]
2.(a) Derive one-dimensional, time independent Schrodinger wave equation for an
electron.
(b) What is the physical significance of wave function?
(c) An electron is confined to a box of length 10-8m. Calculate the minimum
uncertainty in velocity.
3.(a) What is Fermi energy? Explain.
(b) Explain the Fermi-Dirac distribution function of electrons. Illustrate graphi-
cally the effect of temperature on the distribution.
(c) The Fermi energy of silver is 5.5 eV. An electron in silver has an energy
which is 1% above Fermi energy. At what temperature we can expect a 10%
probability of electron at this energy level?
4. (a) Explain the terms:
i. Magnetic flux density
ii. Magnetic field strength
iii. Magnetization and
iv. Magnetic susceptibility. How they are related to each other?
(b) What are hard and soft magnetic materials? Write their characteristic prop
erties and applications.
5. (a) Write a note on intrinsic semiconductors.
(b) Derive an expression for the number of electrons per unit volume in the con-
duction band of an intrinsic semiconductor.
6. (a) Explain the characteristics of a LASER.
(b) Describe the construction and working of Ruby laser.
(c) Write any four applications of laser.
7. (a) Explain the advantages of optical fiber in communication.
(b) Discuss different losses in optical fibers.
(c) The refractive indices of core and cladding are 1.53 and 1.42 respectively. Then
calculate its critical angle.
8. (a) What are nanomaterials? Explain.
(b) Describe the various types of carbon nanotubes.
(c) Explain the fabrication of carbon nanotubes.
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