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BSc (VI Semester) Examination
PHYSICS
Paper : PHY–362 (Old Course)
( Solid-state Physics )
Full Marks : 80
Pass Marks : 35%
Time : Three Hours
Note : 1. Answer any five questions.
2. The figures in the margin indicate full marks for the questions.
1. (a) Explain the concepts of lattice, basis and crystal structure. How are they related? 6
(b) What are the amorphous materials? Give examples of such materials. Define the primitive and non primitive translation vectors. 1+1+2=4
(c) What are the Brillouin zones? Discuss the construction of the first three Brillouin zones for a square lattice. 6
2. (a) How does the Fermi energy of a metal depend on temperature, concentration of electrons and the total number of electrons present in the metal? The atomic radius of sodium is 1·86 Å. Calculate the Fermi energy of sodium at absolute zero. 5+5=10
(b) Distinguish between metals, insulators and semiconductors on the basis of band theory of solid. 6
3. (a) State and prove the Bloch theorem. Discuss its importance in the band theory. 12
(b) How does a free electron gas differ from an ordinary gas? 4
4. (a) Explain the difference between the terms ‘Curie temperature’ and ‘Neel temperature’. 6
(b) What is the essential difference between the classical theory and the quantum theory of para magnetism? 10
5. (a) What is Meissner effect? Explain the difference between type I and type II superconductors using the Meissner effect. 10
(b) What are London equation and coherence length? 6
6. (a) What is a phonon? Give an evidence for the existence of phonons. What is meant by acoustical mode of wave propagation in a diatomic crystal? 1+2+3=6
(b) Discuss the Debye model of lattice heat capacity. What is Debye law? 4+6=10
7. Write short notes on any four of the following : 4×4=16
(a) X-ray diffraction
(b) Density of states
(c) Continuous solid
(d) Kronig-Penney model
(e) Hysteresis
(f) Coercivity
(g) Critical temperature
