# JNTU previous year question papers B -Tech Supplimentary Examinations, Engineering physics- Aug/Sep 2008

JNTU previous year question papers

JNTU B.Tech Supplimentary Examinations, Aug/Sep 2008

ENGINEERING PHYSICS

SET-IV

1. (a) Give the theory of interference and obtain the condition for constructive and

destructive interference.

(b) Light waves of wavelength 650 nm and 500 nm produce interference fringes on

a screen at a distance of 1 m from a double slit of separation 0.5 mm. Find

the least distance of a point from the central maximum where bright fringe

due to both coincide.

2. (a) What is meant by polarization of light?

(b) Describe an experiment that shows light is not propagated as longitudinal

waves.

(c) What is plane of vibration?

3. (a) What is reverberation time?

(b) Explain how the sound absorption coefficient of a material is determined.

(c) The reverberation time is found to be 1.5 sec. for an empty hall and it is found

to be 1.0 sec when a curtain cloth of 20 m2 is suspended at the centre of the

hall. If the dimensions of the hall are 10 × 8 × 6 m3, calculate the coefficient

of absorption of curtain cloth.

4. (a) Explain the need of a cavity resonator in a laser.

(b) With the help of suitable diagrams, explain the principle, construction and

working of a Ruby laser.

5. (a) Explain the principle behind the functioning of an optical fibre.

(b) Derive an expression for acceptance angle for an optical fibre. How it is related

to numerical aperture?

(c) An optical fibre has a numerical aperture of 0.20 and a cladding refractive index of 1.59. Find the refractive index of core and the acceptance angle for the fibre in water which has a refractive index of 1.33.

6. (a) Define crystal lattice, unit cell, lattice parameter and co-ordination number.

(b) Consider a Body Centered Cubic lattice of identical atoms having radius R.

Compute

i. the number of atoms per unit cell

ii. the co-ordination number and

iii. the packing fraction.

7. (a) Derive Bragg’s law of X-ray diffraction.

(b) Describe Bragg’s X-ray spectrometer and explain how Bragg’s law can be verified.

(c) Monochromatic X-rays of ?=1.5 A.U. are incident on a crystal face having an interplanar spacing of 1.6 A.U. Find the highest order for which Bragg’s reflection maximum can be seen.

8. (a) Give an account on the effects of dislocations on the properties of solids.

(b) Explain the significance of Burgers vector.