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BSc (VI Semester) Examination
PHYSICS
Paper : PHY–362 (New Course)
( Solid-state Physics )
Full Marks : 80
Pass Marks : 35%
Time : Three Hours
Note : 1. Answer eight questions in which Question No. 1 is compulsory.
2. The figures in the margin indicate full marks for the questions.
1. (a) What are the amorphous materials? Give examples of such materials. 2
(b) Define the primitive and nonprimitive translation vectors. 2
(c) How does a free electron gas differ from an ordinary gas? 2
(d) What is a phonon? Give an evidence for the existence of phonons. 2
(e) Give any two characteristics of a superconductor. 2
2. (a) Explain the concepts of lattice, basis and crystal structure. How are they related? 5
(b) What are the Brillouin zones? Discuss the construction of the first three Brillouin zones for a square lattice. 5
3. (a) Define cohesive energy and determine its value for crystals of inert gases. 7
(b) What are the covalent crystals? Give two examples. 3
4. (a) Discuss the Debye model of lattice heat capacity. What is Debye law? 8
(b) What is meant by acoustical mode of wave propagation in a diatomic crystal? 2
5. (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? 5
(b) The atomic radius of sodium is 1·86 Å. Calculate the Fermi energy of sodium at absolute zero. 5
6. State and prove the Bloch theorem. Discuss its importance in the band theory. 10
7. (a) Define the Fermi level. What is its importance in semiconductor materials? 5
(b) Distinguish between the intrinsic and extrinsic semiconductors. 5
8. Discuss the Langevin’s theory of paramagnetism and derive the expression of Curie temperature. 10
9. Explain the following terms briefly : 2×5=10
(a) Hysteresis
(b) Coercivity
(c) Critical temperature
(d) Domains
(e) Permeability
10. (a) What is Meissner effect? Explain the difference between type I and type II superconductors using the Meissner effect. 5
(b) What are London equation and coherence length? 5
11. Write short notes on any two of the following : 5×2=10
(a) X-ray diffraction
(b) Density of States
(c) Continuous solid
(d) Kronig-Penney model
