RR
Code No: RR100203
I B.Tech (RR) Supplementary Examinations, June 2009 SOLID STATE PHYSICS (Common to Electrical & Electronics Engineering, Electronics & Communication Engineering, Computer Science & Engineering, Electronics & Instrumentation Engineering, Bio-Medical Engineering, Information Technology, Electronics & Control Engineering, Computer Science & Systems Engineering, Electronics & Computer Engineering and Instrumentation & Control Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ????? 1. (a) Plot and explain the variation of i. attractive potential energy ii. repulsive potential energy iii. resultant potential energy with interatomic distance, when two atoms are brought nearer. (b) Estimate the bond energy for the NaCl molecule as formed from sodium and chlorine atoms. The inter ionic equilibrium distance is 236 pm. Born constant is 8. The ionization energy of sodium is 5.14 eV and electron affinity of chlorine is 3.65 eV. [10+6] 2. (a) Deduce the expression for the inter-planar distance in terms of Miller indices for a cubic structure. (b) Sketch the following planes of a cubic unit cell: (0 0 1), (1 2 0) and ( 2 1 1). (c) Calculate the ration d100 : d110 : d111 for a simple cubic structure. [8+4+4] 3. (a) Explain the physical significance of wave function. (b) Assuming the time independent Schrodinger’s wave equation, discuss the solution for a particle in a one-dimensional potential well of infinite height. (c) A quantum particle confined to one-dimensional box of width ‘a’ is known to be in its first excited state. Determine the probability of the particle in the central half. [4+6+6] 4. (a) Explain the origin of energy bands in solids. (b) Assuming the electron - lattice interaction to be responsible for scattering of conduction electrons in a metal, obtain an expression for conductivity in terms of relaxation time and explain any three draw backs of classical theory of free electrons. (c) Find the temperature at which there is 1% probability of a state with an energy 0.5 eV above Fermi energy. [6+6+4] 5. (a) What are the important characteristics of ferro-electric materials? (b) Describe the possible mechanism of polarization in a dielectric material. (c) The dielectric constant of Helium gas at NTP is 1.0000684. Calculate the electronic polarisability of He atoms if the gas contains 2.7 × 1025 atoms / m3 . [6+6+4] 6. (a) What are the characteristics of soft magnetic materials? (b) What is ferro-magnetic Curie temperature? Discuss the behaviour of a ferro- magnetic material below the Curie temperature. (c) The magnetic field in the interior of a certain solenoid has the value of 6.5 × 10−4 T when the solenoid is empty. When it is filled with iron, the field becomes 1.4 T. Find the relative permeability of iron. [6+6+4] 7. (a) Distinguish between metals, semiconductors and insulators. (b) Explain the effect of temperature on resistivity of a semiconductor. (c) Derive an expression for the number of electrons per unit volume in the conduction band of an intrinsic semiconductor. [6+4+6] 8. (a) Explain the purpose of an active medium in a gas laser. (b) With the help of suitable diagrams, explain the principle, construction and working of a heliumneon laser. [6+10] ?????