Physics Ii Dec 2002

· B. E. IInd Semester Examination, December-2002

PHYSICS-II Paper-Phy-102 C Maximum Marks: 100

TIme allowed : 3 hours

Note: Attempt five questions in all, selecting at least two questions from each part.

Part-A Discuss mechanisms of dielectric polarization. Show

1. (a)

how presence of a dielectric medium modifies the otherwise existing electric field. 13 (b)

Briefly explain the principle and working of a betatron.

2.

7

Discuss the propagation of electromagnetic '·vaves in a conducting medium and hence define 'skin depth'. Explain significance of skin depth in daily life. 20

3. (a) (b)

4. (a)

Explain de-Broglie concept of matter-waves. Discuss experimental evidence in support of the concept. 13 Life time of an excited state of electron is 1 O~ sec. Calculate the uncertainty in the frequency of the radiation emitted when the electron returns to the 7 ground state. Discuss Schrodinger wave equation. Explain the significance of wave vector. 7 A particle is

(b)

constrained to have only one-dimensional motion in the limits x = 0 and x = L. Derive expression

320-A-400 P-2 (Q-8)

P.T.O.

for the eigenfunctions and energy eigenvalues allowed to the particle.

13

Part-B S. (a)

Define Crystal, Unit cell and Fundamental translation vectors.

(b)

6

What are Miller Indices ? How Miller Indices of a crystallographic direction and a crystallographic plane are specified ?

(c)

Sketch the planes with the following Miller Indices:

(110), (234) and (43T).

6. (a)

8

6

Explain the terms: Energy band, Forbidden region, Valancy band, Conduction band and Energy gap. 7

(b)

Show that a completely filled energy band does not contribute to electrical conductivity.

7.

13

Distinguish between intrinsic and extrinsic semiconductors. Derive expressions to show how Fermi level and conductivity of an intrinsic semiconductor depend on temperature. 20

8. (a)

Discuss experimental facts about variation of specific heat of solids with temperature. 6

(bj

Explaining mail! as~umptions of Einstein'" model, show'how far it could explain the experimental facts regarding specific heat of solids. 14

320-A-400