Solid State Physics — DU B.Sc. (Hons) Physics Previous Year Question Papers

Du.ration: 3 Hours Department of physics & Astrophysics B.Sc. Hons. NEP GH Solid State Physics Maximum Marlrs: 90 (a) In 2D structures there is no centred square Bravais lattice. Give your argument to prove that the centred square is not a new lattice. a) Differentiate between Amorphous and Crystalline materials. Give one example of each. (c) The Hall coefficient of a certain silicon specimen was found to be -6.24*10-5 m3C-I from 100 K to 400 K. Determine the nature of the semiconductor. Further, the electrical conductivity was found to be 200 a-]m-I. Calculate the density and mobility of charge carriers. (d) What do you understand by effective mass of electrons? (e) The critical magnetic field for Aluminium is 4.5xl05 A/in. Calculate the critical current which can flow through a long thin superconducting wire of Aluminium of diameter 1 o-4m. 2.(a) Prove that the volume of a unit cell in the reciprocal lattice is inversely proportional to the volume of a unit cell in the direct lattice. (5) (b) Define Brillouin zones? Draw fii.st two Brillouin zones of a square lattice? (7.5) (c) Show that for hexagonal close packed structure c/a =/575 , where a and c are the lattice parameters. (5) 3(a) Derive an expression for the dispersion relation for the monoatomic linear chain of atoms and show that how it behaves as a low pass filter. (10) (b)The dispersion relation for the vibrational modes of diatomic linear lattice having massesmandM(m<xpco4]S_2ff(i+i)co2+#Sm2Ka=° where the symbols have their usual meanings. Obtain expressions for acoustical and ^optical curves. Als.o draw the dispersion curves. 4(a) Write the assumptions taken in the formulation of Kronig-Penney model to describe the formation of energy bands in solids. Describe the argument for taking the wave function of electron as a Bloch function? (7.5) (b) Show that for the free electrons, the effective mass of electron is equal to the free electron mass. (c) Calculate the number of energy states available for the electrons in a cubical box of side 1 cm lying below the energy of 1 eV. reason one practical application each of a soft and hard material. (b) A magnetic material has a magnetization of 3300 A-m'' and flux density of 0.0044 Wb-m?. Calculate the magnetizing force and the relative permeability of the material. 6(a) what do you understand by dielectric, dipole moment, dielectric polarization, and depolarization. Show that D= & Et P where symbols have their usual meaning. (b) What are polar and non-polar molecules? Give examples. Also calculate the electric susceptibility for a dielectric material having dielectric constant 1.329. (c) The capacitance of a parallel capacitor increases from 0.085uF to 0.195uF when a sheet of polythene is placed between the plate. Determine the dielectric constant of polythene. 7.(a) State and explain Meissner effect. Show that this law violates the classical law? (b) Discuss application of superconductors in power transmission and magnetic