LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

M.Sc. DEGREE EXAMINATION – PHYSICS

FOURTH SEMESTER – NOVEMBER 2003

PH 4801 / PH 1017 – SOLID STATE PHYSICS II

 

30.10.2003                                                                                          Max.   : 100 Marks

1.00 – 4.00

 

 

PART – A

 

Answer all the questions.                                                                                 (10 x 2 = 20)

 

1. Explain the physical basis of the effective mass.

 

2. Discuss the Mott – metal insulation transition with a suitable example.

 

3. List the microwave and infrared properties of superconductors.

 

4. Outline briefly, the various methods of measuring the B.E of excitons.

 

5. Explain the nature of piezoelectricity and hence obtain the piezoelectric equations for polarization and elastic strain.

 

6. What is meant by “zero field splitting”?

 

7. Discuss the role of isotope effect on superconductivity.

 

8. With necessary diagrams, explain the mechanism responsible for the mobility of a dislocation.

 

9. Distinguish between the Burger vector of a screw dislocation and that of an edge dislocation.

 

10. Explain the formation of a hole trapped color centre with suitable example.

 

PART – B

 

Answer any FOUR questions only                                                                   (4 x 7.5 = 30)

 

11. Explain the thermoelectric effects in semiconductors and hence obtain the Kelvin’s relation for irreversible thermodynamics.

 

12. Derive the dispersion relation for electromagnetic waves and discuss in detail the conditions to be satisfied for the propagation or attenuation of em waves.

 

13. State the essential conditions required in the formation of Freckle exciton and obtain the energy eigen values.

 

14. Explain the thermodynamics of the super conducting transition and obtain the expression for stabilization energy density of the super conducting state at absolute zero.

 

15. Discuss in detail, the Landau’s theory of phase transition and explain the second order phase transition.

-2-

 

 

PART – C

 

Answer any FOUR questions only.                                                                (4 x 12.5 = 50)

 

16. Derive the expression for the intrinsic carrier concentration and hence form the law of mass action. Prove that the Fermi level lies in the middle of the forbidden gap.

 

17. a) Discuss in detail, the electrostatic screening behavior of electron gas and obtain the

relation connecting the es potential and charge concentration.                             (7)

 

5. Using the Thomas-Fermi approximation, derive the expression for the dielectric function of an electron gas.             (5.5)

 

18. a) Distinguish between A.C. Josephson and D.C. Josephson effects. (3.5)

 

1. b) Prove that the current of superconductor pairs across the junction depends on the phase difference  in the case of D.C Josephon effect.                                                       (9)

 

19. Derive the Block equations of motion and obtain the equations for (i) the power absorption and (ii) half width of the resonance at half maximum power.

 

20. a) What are lattice vacancies? Explain the mechanisms of forming the Schottky and Freckle defects with relevant diagrams.             (5.5)

 

1. b) Derive the expression for the number of defects formed in the Schottky type with special references to ionic crystals. (7)

 

 

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LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

M.Sc. DEGREE EXAMINATION – PHYSICS

FOURTH SEMESTER – APRIL 2012

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)

 

1. What are direct and indirect band semiconductors ?
2. Show that n₀ p₀ is independent of the position of the Fermi level.
3. Establish the relation between relative permeability and magnetic susceptibility.
4. Evaluate Lande’s g factor for S=0.
5. What is pyroelectric effect?
6. What is photoconductivity?
7. Explain ferri-electricity.
8. What is the working principle of a Maser?
9. Mention the three critical parameters of a super conductor.
10. Explain isotope effect in superconductivity.

 

PART – B

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

 

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

                                   

PART – C

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

 

16. (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_p are 0.39 and 0.19 m²v^-1s^-1 , E_g is 0.72eV and C is 4.8 x10 ²¹                           (4)

17. (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.

19. (a) Explain classical theory of dia-magnetism.

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

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

 

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