BSc Physics SEM V 2018 19 2018-19 Physics II Solid State Physics 19 Old Question Paper - Mumbai University | munotes

Questions asked in this paper

• (2) Figures to the right indicate full marks

1. Q1 Charge on electron
2. Q4 Velocity of lightin vacuum c=3x
3. Q5 Permeability of free space = 1.257 x
4. Q6 Permittivity of free space = 8.85 x C?/ N-m?
5. Q8 Boltzmann constant k=1.38 x
6. Q1 (a) Attempt any one: Explain thermionic emission in metals. Derive an expression for the 10
   • (ii) Derive the expression of Fermi energy and average energy of electron at absolute zero. Assume the expression of density of states
   • (b) Attempt any one:
   • (i) Explain drift velocity, relaxation time and mean free path as applied to free 5 electron in.a metal
   • (ii) Find the temperature at which there is 1% probability that a state with 5 energy 0.5 eV above fermi energy will be occupied
7. Q2 (a) Attempt any one:
   • (i). Discuss the Kronig- Penney model for behavior of an electron in a dimensional periodic lattice. Show that it leads to the occurrence of allowed and forbidden bands for the electrons Explain Meissner effect in superconductors. Hence discuss Type I and Paper Subject Code: 24179 Physics : Paper II - Solid State Physics. (Old)
   • (b) Attempt any one:
   • (i) Explain how materials can be classified into conductors, insulators and 5 semiconductors on the basis of E-K curve for the materials
   • (ii) The critical temperature for a superconductor is 6.4 K in zero magnetic field. The critical magnetic field for the same material at 0 K is A/m. Find the critical field at 3.6 K and 1K
8. Q3 (a) Attempt any one:
   • (i) Explain Langevin’s classical theory of Paramagnetism. Derive an expression for 10 the paramagnetic susceptibility of metal at ordinary temperature and normal field
   • (ii) | Discuss Weiss field theory of Ferromagnetism. Hence derive a relation 10 ferromagnetic Curie temperature and Weiss constant
   • (b) Attempt any one: the origin of permanent magnetic dipole moments 5 obtain the relation between magnetic dipole moment and angular momentum of an orbiting electron
   • (ii) A magnetic field strength of a material is A/m.If the magnetic 5 susceptibility of the material is —(0.8 x ), calculate magnetization and
9. Q4 (a) Attempt any one: What is p junction? With the help of energy band diagram of 10 unbiased p-n junction explain the terms: Depletion region and Potential
   • (ii) Derive an expression for electron concentration in an intrinsic 10 semiconductor, hence write the expression for hole concentration at
   • (b) Attempt any one:
   • (i). Draw the volt-ampere characteristics of the p-n junction diode. Explain 5 how they depend on the temperature
   • (i) A germanium p-n junction diode has reverse saturation current of 5 Find its static and dynamic resistance for an applied forward bias of 0.3 V at Paper Subject Code: 24179 Physics : Paper II - Solid State Physics. (Old)
10. Q5 (a) Attempt any one:
    • (i) The density of silver is Kg the atomic weight of silver is 107.9 — 4
    • a.m.u. The conductivity of silver at is 7x107 Calculate the collision time in silver
    • (ii) Find the Fermi velocity and temperature of electron in sodium for 4
    • (b) Attempt any one:
    • (i) Calculate critical current through Tungsten wire of diameter 2.8mm and 4
    • (ii) A two dimensional square lattice side of 0.85 nm. Calculate 4 momentum and energy of the free electron of first Brillion zone
    • (c) Attempt any one:
    • (i) Consider helium atom in its ground state. The mean radius is 0.528nm. 4 Density of helium is 0.178kg/m? Calculate the diamagnetic susceptibility of the helium atom. Atomic mass of helium = 4.003u
    • (ii) A magnetic material made of steel has a magnetic moment of 3 Am* anda 4 mass of 6 kg. If the density of steel is 7.9 x 107 kg magnetic flux density when it is placed in magnetic field of
    • (d) Attempt any one: intrinsic semiconductor with gap width Eg = 0.7eV, calculate the 3 concentration of intrinsic carrier at 300 K. Given mo = 9.1 x 107! kg, qi) An electric field of 50V/m is applied sample of n-type semiconductor 3 whose Hall coefficient is Determine the carrier charge density (n) in the sample

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