DHAANISH AHMED COLLEGE OF ENGINEERING, PADAPPAI
PH1X01 ENGINEERING PHYSICS
MODEL EXAM MARCH-2008
(COMMON TO ECE-A,ECE-B,CSE-A,CSE-B,B.TECH IT)

TIME : 3 HOURS MAXIMUM MARKS : 100

ANSWER ALL :
Part-A ( 2x 10 = 20)
Define a) Magnetostriction effect and b) Piezo electric effect
Write a note on SONAR
What is known as Numerical Aperture
Differentiate between active and passive fibre optic sensors
Define Wiedemann Franz law
Outline the drawbacks of classical free electron theory
Define Fermi energy
State Stress optic law
The superconducting transition temperature of lead is 7.26 k. The initial field at 0K is 64 x 103 Am-1. Calculate the critical field at 5 K.
Discuss the temperature dependence of Polarisation in dielectrics.

Part B (15 x 16 = 80)
a) Explain the various factors affecting the architectural acoustics of a building
and their remedies.. (16)
or
b) i) Define Packing Factor. (2)
ii) Deduce the c/a ratio and packing factor for HCP structure. (10)
iii)Calculate the Interplanar spacing for (101) and (221) planes in a simple
cubic lattice whose lattice constant is 0.42 nm. ( 4)

a) i) Explain how the wavelength of monochromatic source of light can be
experimentally determined using a Michelson’s Interferometer (8)
ii) Distinguish between a) circularly polarized light and unpolarised light b)
elliptically polarized and partially polarzed light. (8)
Or
b) i) Explain the lasing schemes and working of a Nd: YAG laser. (8)
ii) Explain the construction and working of a CO2 laser. (8)

a) i) Define Compton Effect. (2)
ii) Derive an expression for the wavelength of the scattered photon (Compton
shift). (10)
iii) Find the change in wavelength of a X-ray photon when it is scattered
through an angle of 135 by a free electron.(h = 6.626x 10-34js-1, m0 = 9.1 x .
10-31 kg; c= 3x 108 m/s) (4)
or
b) Derive an expression for the density of energy states and carrier concentration in
a solid material by using the Fermi distribution function. (16)

a) i) Define Hall Effect. (2)
ii) Explain in detail how hall coefficient can be determined experimentally.(10)
iii)The donor density of an n type germanium sample is 1021/m3. The sample is
arranged in a Hall experiment having magnetic field of 0.5 tesla and current
density is 500 ampere/m3. find the hall voltage if the sample is 3 mm
wide.(4)
Or
b) i)Derive the expressions for the electron and hole concentrations in extrinsic
semiconductors . (12)
ii) Discuss with diagrams the variation of Fermi level with temperature in extrinsic
semiconductor. (4)

15 a) Derive an expression for internal field and deduce the Clausius- Mosotti equation.
Or
b) i) Derive time dependent and time independent Schroedinger wave equations (10)
ii) Solve Schroedinger wave equation for a particle in one dimensional box. (16)

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