Model Question Paper with effect from 2017-18
CBCS Scheme
17PHY12/22
First/Second Semester B.E. Degree Examination
Engineering Physics
Time 3 hrs Max. Marks: 100
Note: 1. Answer FIVE full questions, choosing one full question from each module.
2. Physical constants: Velocity of light c 3 108m/s; h 6.625 10 -34JS; k 1.38 10 NA 6.02 10 23/Kmole; me 9.1 10-31kg; e 1.6 10-19C.
Module 1
1 a. What is a black body? Discuss in brief Wien's law and Rayleigh jean's law to explain black body spectrum. Describe ultraviolet catastrophe. marks)
b. State and explain Heisenberg uncertainty principle. Discuss the significance of the principle. Prove that, using uncertainty principle, the electron emitted during is not the preexisted electron in nucleus. marks)
c. An electron is confined to a potential well of infinite height and width 5A0. Calculate the de Broglie wavelength when the electron is in ground state and 3rd excited state marks)
OR
2 a. What are matter waves? Discuss their characteristics marks)
b. Define Phase velocity and Group velocity. Obtain the relation between them and hence show that in a non-dispersion medium the group and phase velocities are same. marks)
c. Write a short note on properties of wave function. marks)
d. Find the kinetic energy of an electron whose de Broglie wavelength is the same as that of a 100keV x-ray. marks)
Module-2
3 a. Define the terms drift velocity, thermal velocity, mean free path and relaxation time. Explain why thermal velocity is not responsible for electric current in a conductor. marks)
b. Explain briefly the formation of cooper pairs and hence BCS theory marks)
c. Discuss any three major failures of classical free electron theory. marks)
d. For a metal having 6.5 x 10 28 free electrons per unit volume the relaxation time at room temperature 300K is 3.82 x 10 -14 second. Calculate its electrical resistivity using classical free electron theory marks)
OR
4 a. What is a super conductor? Explain Meissner effect marks)
b. Give the expressions for concentration of electrons and holes in an intrinsic semi-conductor. Obtain the expression for electrical conductivity of intrinsic semiconductor. marks)
c. What is Fermi-Dirac statistics? Explain marks)
d. A superconducting tin has a critical temperature at 3.7K in zero magnetic fields and a critical field of 0.0306 T at 0K. Find the critical field at TC. marks)
Module-3
5 a. State and explain the necessary conditions for laser marks)
b. With a neat diagram explain the construction and working of semiconductor laser marks)
c. Describe briefly the application of laser in welding and cutting (4marks)
d. The angle of acceptance of an optical fiber is 300 when kept in air. Find the angle of acceptance when it is in a medium of RI 1.33 marks)
OR
6 a. What is attenuation in optical fiber? Discuss the various loss factors in optical fiber communication marks)
b. Discuss the any three advantages and disadvantages of optical fiber communication system over conventional communication system marks)
c. Mention the applications of holography marks)
d. Calculate on the basis of Einstein's theory, the number of photons emitted per second by laser source emitting light of wavelength 6328A0 with an optical power output 10mW. marks)
Module 4
7 a. Define lattice points, unit cell, Bravais lattice and primitive cell marks)
b. Describe briefly the seven crystal systems marks)
c. Obtain an expression for the inter planar distance in a cubic crystal in terms of Miller indices
marks)
d. The grating space of calcite is 3.036A0 and for the first order Bragg reflection the glancing angle is 120. Find the path difference between the rays marks)
OR
8 a. Discuss the allotropy of carbon with reference to diamond and graphite marks)
b. Give a qualitative explanation of perovskite crystal structure marks)
c. Define coordination number and packing factor. Calculate the packing factor for BCC structure marks)
d. Draw the crystal planes (1110, and 00) in a cubic crystal. marks)
Module 5
9 a. Define Mach number and hence distinguish between subsonic and supersonic waves marks)
b. List the properties of shock waves. Give an example for weak and strong shock waves
marks)
c. With a neat diagram explain the construction and working of Reddy shock tube marks)
d. Discuss the advantages of Sol-Gel method marks)
OR
10 a. With a neat diagram explain how the carbon nano tubes are synthesized using arc discharge method. marks)
b. Describe density of states for various quantum structures marks)
c. Discuss the basics of conservation of mass, momentum and energy marks)