B.E./B.Tech. DEGREE EXAMINATIONS, MAY/JUNE 2010

Regulations 2008

First Semester

Common to all branches

PH2111 Engineering Physics I

Time: Three Hours Maximum: 100 Marks

Answer ALL Questions

Part A - (10 x 2 = 20 Marks)

1. Mention any two properties of ultrasonic waves.2. What i s the principle of pulse echo system?

3. What are the conditions needed for laser action?

4. What is holography?.

5. De¯ne acceptance angle of a ¯bre.

6. Give the applications of the ¯bre optical system.

7. Calculate de Broglie wavelength of an electron moving with velocity 107 m/s.

8. Explain degenerate and non-degenerate states.

9. Calculate the ¯rst and second nearest neighbor distances in the body centered cubic unit

cell of sodium, which has lattice constant of 4:3 £ 10¡10 m.

10. What is meant by Frenkel imperfection?

Part B - (5 x 16 = 80 Marks)

11. (a) (i) What are magnetostriction and piezoelectric e®ect? (4)(ii) Write down the complete experimental procedure with a neat circuit diagram of

producing ultrasonic waves by piezoelectric e®ect. (12)

OR

11. (b) (i) What is an acoustic grating? How is it used in determining the velocity of

ultrasound?

(2 + 6)

(ii) Explain the process of non-destructive testing of materials using ultrasonic waves

by pulse-echo method. (8)

12. (a) (i) Derive the relation between the probabilities of spontaneous emission and stimu-

lated emission in terms of Einstein's coe±cients. (8)

(ii) Explain the following pumping mechanisms.

(1) optical and

(2) electric discharge. (8)

OR

12. (b) (i) With a neat sketch, explain the construction, principle and working of CO2 laser.

(14)

(ii) Mention four applications of lasers in materials processing.

(2)

13. (a) (i) Explain the basic structure of an optical ¯bre and discuss the principle of trans-

mission of light through optical ¯bres. (5)

(ii) Derive an expression for numerical aperture. (5)

(iii) Brie°y discuss a technique of optical ¯bre drawing. (6)

OR

13. (b) (i) With a neat diagram, give an account on displacement sensors. (8)

(ii) Give an elaborate account on losses in optical ¯bres. (8)

14. (a) (i) What is Compton e®ect? Derive an expression for the change in wavelength

su®ered by an X-ray photon, when it collides with an electron. (2 + 12)

(ii) An electron at rest is accelerated through a potential of 2 kV. Calculate the de

Broglie wavelength of matter wave associated with it. (2)

OR

14. (b) (i) Solve the Schrodinger's wave equation for a free particle of mass m moving within

a one dimensional potential box of width L to obtain eigenvalues of energy and

eigenfunctions.

(11)

(ii) Find the eigenvalues of energies and eigenfunctions of an electron moving in a

one dimensional potential box of in¯nite height and 1 ÂșA of width. Given that m

= 9.11 £10¡31 kg and h = 6.63 £10¡34 J. (5)

15. (a) (i) What are Miller indices? Mention the steps involved to determine the Miller

indices with example. (2 + 4)

(ii) The material zinc has HCP structure. If the radius of the atom is

1

4

th of the

diagonal of hexagon, calculate the height of the unit cell in terms of atomic

radius.

(2)

(iii) Show that the packing factor for HCP i s 74% . (8)

OR

15. (b) (i) What i s Burger vector? (2)

(ii) Draw Burger circuit indicating Burger vector for edge dislocation and screw dis-

location. (4+4)

(iii) Certain defects in crystals improve the properties of crystals. Explain. (6)

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