PH 4806 – SOLID STATE PHYSICS – II

Date : 16-04-2012 Dept. No. Max. : 100 Marks

Time : 1:00 – 4:00

PART – A

Answer ALL questions: (10×2=20)

What are direct and indirect band semiconductors ?
Show that n₀p₀ is independent of the position of the Fermi level.
Establish the relation between relative permeability and magnetic susceptibility.
Evaluate Lande’s g factor for S=0.
What is pyroelectric effect?
What is photoconductivity?
Explain ferri-electricity.
What is the working principle of a Maser?
Mention the three critical parameters of a super conductor.
Explain isotope effect in superconductivity.

PART – B

Answer any FOUR questions: (4×7.5 = 30)

Explain the effect of temperature on the mobility of charge carriers in a semiconductor.
Give the classical theory of electronic polarisation.
Explain the phenomenon of absorption in semiconductors and the role of excitons.
Derive an expression for anti ferro magnetic susceptibility.
Write a short note on high temperature superconductivity.

PART – C

Answer any FOUR questions : (4×12.5 =50)

(a) Explain with suitable energy level diagrams the rectifying effect at a metal semiconductor junction. (8.5)

(b). Calculate the intrinsic conductivity σ_i at 300K for germanium. Given μ_e and μ_pare 0.39 and 0.19 m²v^-1s^-1 , E_gis 0.72eV and C is 4.8 x10 ²¹ (4)

(a) Derive an expression for the local field in a dielectric.

(b) Establish the Clausius-Mossotti equation. (5)

18 . (a) Explain the phenomenon of photoluminiscence. (5)

(b) Derive expressions for Einstein coefficients of stimulated emission.

(a) Explain classical theory of dia-magnetism.

(b) What are ferrites? Give any two examples. (4)

Briefly outline the BCS theory of superconductivity and derive an approximate expression for the transition temperature.

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