BSc Physics SEM V ATKT May 2018-19 ATKT PHYSICS SOLID STSTE PHYSICS Question Paper - Mumbai University | munotes

Questions asked in this paper

• (2) Figures to the right indicate full marks

1. Q1 Attempt any two:
   • (a) crystal, deduce an expression for interplanar distance for planes 10 of Miller indices (hk 1)
   • (b) Define ‘Primitive cell’ and * Non-primitive cell’. Explain the terms ‘Atomic- 10 radius’ and ‘Atomic packing fraction’. Obtain packing fraction for a body
   • (c) With the help of a neat diagram, explain seven crystal systems and fourteen 10 2 Attempt any two:
   • (a) Write down one main feature of the ‘Sommerfeld free electron model’. Hence, 10 obtain an expression for the density of states for the potential energy box of On the basis of quantum theory, derive an expression for the electrical 10 conductivity of metal. Modify it on the basis of band theory
   • (c) What is meant by Thermionic emission’? derive Richardson-Dushman 10
2. Q3 Attempt any two:
   • (a) Derive an expression for the concentration of electrons in an intrinsic 10
   • (b) Using Kroning Penney model, obtain solution of Schrodinger’s equation for an 10 electron in a periodic potential
   • (c) Set up the continuity equation for the charge carriers in a semiconductors. 10 Paper Subject Code: 24225 Physics: Solid State Physics
3. Q4 Attempt any two:
   • (a) Explain the band structure of an open circuited p-n junction with the help of 10 neat diagram. Derive an expression for the contact difference Eo of the junction
   • (b) What is superconductivity? Explain and distinguish between Type I and Type 10
   • (c) Derive the law of junction assuming low level injection for a p-n junction 10
4. Q5 Attempt any Four:
   • (i) Show that for a cubic fcc crystal, the lattice constant is given by 05 where M is the molecular weight of molecules at lattice points, d is the density of a crystal and N is. Avogadro’s number
   • (ii) are accelerated by 844 V and are reflected from 05 Calculate the spacing of the crystal; if the maximum reflection occurs at the glancing angle of 58 degree
   • (iii) Resistivity of an uniform Silver wire is 1.54 x Q-m.at room 05 temperature. Compute the average drift velocity of an electrons, their mobility and also relaxation time. Assume an electric field is of along the wire and there are 5.8 x conduction electrons per meter
   • (iv) At what temperature we can expect a 10.% probability that electrons in 05 a Silver possess an energy that is 1% above the Fermi-energy. Given Fermi-energy of Silver is 5.5 eV The minority carrier life time in p-type material is s. The mobility 05 of electron in silicon is 0.15 m? /VS. Find the diffusion length of
   • (vi) Consider a two dimensional square lattice of side 0.3 nm. At what 05 electron momentum values do the sides of the first Brillouin zone come? What is the energy of the free electron with this momentum?
   • (vii) The lead material works as a superconductor at a temperature of 05 Tc = 7.26 K. If the constant characteristics field of the lead material at 0K is Ho=8 A/m. Calculate the critical magnetic field at 5K A germanium p-n junction has reverse saturation current, = 2u, at Find its static and dynamic resistance for an applied forward bias

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