JNTU Previous year Question paper, B.Tech Supplimentary Exam, Engineering physics – Aug/Sep 2008

JNTU Previous year Question paper

JNTU B.Tech Supplimentary Examinations, Aug/Sep 2008




1. (a) Give the analytical treatment of interference of light and hence obtain the

condition for maximum and minimum intensity.

(b) Two coherent sources of intensity 100 Wm?2 and 25 Wm?2 interfere to form

fringes. Find the ratio of maximum intensity to minimum intensity.


2. (a) Discuss the various methods by which polarized light can be produced.

(b) A beam of linearly polarized light is changed into circularly polarized by pass-

ing it through a 30 ?m thick birefringent crystal. Assuming its thickness is

minimum and for a light of wavelength 589.3 nm incident on it normally, find

the difference of refractive indices of the ordinary and extra-ordinary rays.


3. (a) Explain in detail the basic requirements of an acoustically good hall.

(b) For an empty auditorium of size 20 × 15 × 10 m3, the reverberation time

is 3.5 sec. Calculate the average absorption co-efficient of the auditorium.

What area of the wall should be covered by the curtain so as to reduce the

reverberation time to 2.5 sec? Given that the absorption co-efficient of curtain

cloth is 0.5.


4. (a) Explain the terms:

i. temporal coherence

ii. population inversion

iii. metastable state

iv. stimulated emission

(b) Why is the optical resonator required in lasers? Illustrate your answer with

neat sketches.


5. (a) What is the principle of optical fibre communication? Explain.

(b) Discuss various types of fibres for light wave communication.


6. (a) Explain the origin of permanent magnetic dipole moment.

(b) Explain the existence of spontaneous magnetization in ferro-magnetic materials.

(c) The magnetic susceptibility of copper is -0.5 × 10?5. Calculate the magnetic

moment per unit volume in copper when subjected to a field whose magnitude

in side copper is 104 amp/m.


7. (a) What are Miller indices? Draw (111) and (110) planes in a cubic lattice.

(b) Explain Bragg’s law of X-ray diffraction.

(c) The Bragg’s angle for reflection from the (111) plane in a FCC crystal in the

first order, is 19.2o for an X-ray wavelength of 1.54 A.U. Compute the cube

edge of the unit cell.


8. (a) Explain the various point defects in a crystal.

(b) Obtain the expression for the equilibrium concentration of vacancies in a solid

at a given temperature.

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