Applied Physics 1 - Dec 2013

First Year Engineering (Semester 1)

TOTAL MARKS: 60
TOTAL TIME: 2 HOURS (1) Question 1 is compulsory.
(2) Attempt any three from the remaining questions.
(3) Use suitable data wherever required.
(4) Figures to the right indicate full marks.

Slove any five from the following

1 (a) Define the term space lattice, unit cell and lattice parameter.(3 marks) 1 (b) Find the interplaner spacing between the family of planes (111) in a crystal of lattice constant 3A?.(3 marks) 1 (c) Represent the following in the cubic unit cell :-
(IT2), (002), [121] (3 marks) 1 (d) Define drift current, diffusion current and mobility of charge carriers.(3 marks) 1 (e) Explain the use of P-N junction as a solar cell.(3 marks) 1 (f) State with neat diagram direct and inverse Piezoelectric effect.(3 marks) 1 (g) What is magnetic circuit? Explain Ohm's Law on case of magnetic circuit.(3 marks) 2 (a) Explain the hall effect in metal ? Derive the formulae to determine the density and mobility of the electrons.(8 marks) 2 (b) Define ligancy and critical radius ratio in case of ionic solid. Write the conditions for stability of ionic crystal in 3-D ? Determine critical radius ratio for ligancy 6.(7 marks) 3 (a) Explain with neat diagram construction of Bragg's X-ray spectrometer ? Write the procedure to determine crystal structure. Calculate the maximum order of diffraction if X-ray of wave length 0.819 A? is incident on a crystal of lattice spacing 0.282 nm.(8 marks) 3 (b) Calculate the number of turns required to produce a magnetic flux of 4 x 10⁵ wb, if iron rod of length 50cm and cross sectional area 4 cm² carrying an electric current 1A is in the form of ring.(Permeability of iron is 65 x 10^-4 H/m).(7 marks) 4 (a) What is mesomorphic state of matter ? Explain with neat diagram cholesteric phase.(5 marks) 4 (b) What is dielectric polarization and dielectric susceptibility? Find the relation between them?(5 marks) 4 (c) The resistivity of intrinsic InSb at room temperature is 2 x 10^-4? cm. if the mobility of electron is 6m²/V-Sec and mobility of hole is 0-2 m²/V-Sec. calculate its instrinsic carrier density.(5 marks) 5 (a) Identify the crystal structure if its density is 9.6 x 10² kg/m³, lattice constant is 4.3 A? and atomic weight is 23.(5 marks) 5 (b) Explain the formation of depletion region in P-N junction.(5 marks) 5 (c) Define reverberation time ? State Sabine's formula and explain the terms involved in it?(5 marks) 6 (a) What are soft and Hard magnetic materials ? State their properties and applications.(5 marks) 6 (b) What is Fermi level in semiconductor? Show that in intrinsic semiconductor Fermi level always at the middle between the forbidden energy gap?(5 marks) 6 (c) An Ultrasonic sound wave is used to detect the position of defect in a steel bar of thickness 50 cm. if the echo times are 40 and 90 ?-sec. Locate the position of defect.(5 marks)