### M.SC PHYSICS QUESTION PAPERS

KARNATAKA STATE OPEN UNIVERSITY

Model Question Paper PHYSICS:
MP 2.1- Classical Electrodynamics and Optics
Time: 3 Hours Max. Marks: 80

Instructions: Questions from 1 to 8 carry 15 marks each. Question No. 9 carries 20 marks

1. (a) Define electromagnetic potentials. Express Maxwell’s equations in terms of the electromagnetic potentials. (10)
(b) Show that the gauge transforms A' and  ' satisfy the Lorentz condition if and only if the gauge functions satisfy the wave equation. (5) OR
2. (a) Obtain an expression for Lienard-Wiechert potentials of a moving point charge. (10)
(b) Show that under Lorentz gauge E  and B  also satisfy the wave equation. (5)
3 .(a) Deduce the Abraham-Lorentz formula for radiation reaction and explain its significance. (10)
(b) Show that the expression of power radiated by an oscillating electric dipole leads to Larmor’s formula. (5) OR
4 .(a) Derive expression for the power radiated by an oscillating electric dipole. (10)
(b) Write a note on Pinch effect. (5) 5. (a) Deduce an expression for Poynting vector and discuss the importance of Poynting theorem. (10) (b) Starting from Fresnel’s equations obtain Brewster’s law. (5) OR 6 .(a) Obtain an expression for Clausius- Mossotti equation for electric fields in solids. (10) (b) Write a note on retardation plates. (5) 7. (a) Give the theory of multiple reflections from a plane parallel film. (10) (b) Note down the conditions for sustainable interference. (5) OR 8. (a) Give a detailed description of diffraction at a circular aperture. (10) (b) Discuss Fresnel’s diffraction in brief. (5)9. Answer any four of the following: ( 4X5=20) (a) Obtain an expression for electric quadrupole moment. (b) Show that when the velocity is zero, the Lienard-Wiechert potentials generate electrostatic potential. (c) Obtain an expression for power radiated by an accelerated charge when its acceleration is collinear to its velocity (bremsstrahlung). (d) Show that E B   and 2 2 2 E c B  are Lorentz invariant. (e) Write a note on crystal polarizers. (f) Obtain an expression for Alfven velocity of a plasma wave. (g) Discuss in brief about spatial coherence. (h) Discuss about resolving power of Fabry-Perot etalon.