BSc Sem V 2015 2016 2016 Physics Question Paper - Mumbai University | munotes

Questions asked in this paper

• (2) Figures to the right indicate full marks

1. Q1 (a) Attempt any one : 10 marks
   • (i) Explain relaxation time, collision time and mean free path as applied electrons in metals
   • (ii) Derive an expression for density of energy states of a metal
   • (b) Attempt any one : 5
   • (i) of copper is 8.18x Calculate ermi velocity of electrons in copper
   • (ii) Derive an expression for Fermi energy at zero for a given metal in terms of the number of free electrons per
2. Q2 (a) Attempt any one: AS 10 marks
   • (i) Using E-K curves, derive an for effective number of electrons N,,, energy band of a explain how band theory distinguishes between insulator and semiconductor
   • (ii) What is Meissner effect in Discuss type I and type II
   • (b) Attempt any one: 5
   • (i) Consider square lattice of side 0.3 nm. At what electron momentum the sides of the first Brillouin zone come? What is the energy of the fre electron with this momentum?
   • (ii) Explain ho superconducting transition temperature vary with magnetic field
3. Q3 (a) Attempt 10 marks
   • (i) is diamagnetism? Obtain an expression for the Larmor Frequency of & ession of angular momentum vector about the direction of applied field derive an expression for diamagnetic susceptibility, Discuss the quantum theory of Paramagnetism. Derive an expression for paramagnetic susceptibility at ordinary field strength and normal temperature
   • (i) Give the comparison of the Weiss molecular field theory with the 2 results in ferromagnetic materials
   • (ii) Magnetic field strength in a material is 1200 Adn. If the magnetic susceptibility Magnetization (M) and magnetic density Setup the continuity equation for the charge carriers in a semiconductor Explain the various current components in a biased p-n junction. Derive an for the total current in a p-n diode as a function of the
   • (i) Explain the Hall effect. State the expressions for the Hall Hall
   • (ii) Find the forward current and static (dc) resistance of a p-n germanium diode ifthe temperature is 300 K = for an forward bias voltage of 0.2V. Given: 5 (a) Attempt any one:
   • (i) Discuss the variation of Fermi distribution with temperature
   • (ii) Calculate the electronic contribution to heat of copper using quantum formula at 300 k. Fermi energy 300 K is 7.05 eV
   • (b) Attempt any one:
   • (i) Discuss the conclusion of KronggPenney model with the Scattering power P
   • (ii) The critical temperature is 6.4 K in Zero magnetic field The critical magnetic for the same material at 0 K is 7.5 x Find the critical 6K
   • (c) Attempt any one :
   • (i) Calculate susceptibility at normal temperature for a substance having ‘om/m? and magnetic moment of each atom is 1.6 x A.m?
   • (ii) on "Antiferromagnetism", 3
   • (d) Attempt one :
   • (i) the diffusion coefficient of holes of a single crystal at 300 K, if the of holes is 0,025 a (ii) Explain qualitatively the formation of depletion layer at the junction at thermal

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