LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034
M. Sc. DEGREE EXAMINATION  PHYSICS
THIRD SEMESTER  NOVEMBER 2003
PH 3802 / PH 922 – ELECTRODYNAMICS II
07.11.2003
Max. : 100 Marks
1.00 – 4.00
PART – A
Answer ALL questions.
(10 x 2 = 20)
01. Write down the real electric and magnetic fields for a plane monochromatic wave
of amplitude Eo, frequency w, and phase angle  / 4 that is travelling in the
negative y – direction and polarised in the z – direction
02. What is anomalous dispersion?
03. Why are the ‘retarded potentials’ so called?
04. State the Larmor formula for the power radiated by a moving point charge.
05. Define Contra – and Covariant tensors of rank – 2 by their transformation
properties.
06. What is the Darwin Lagrangian? Give an expression for the same.
07. Write down the electrodynamic boundary conditions near the surface of a perfect
conductor.
08. Distinguish between TM and TE waves.
09. How are the electric and the magnetic fields, in a perfectly conducting fluid,
related?
10. State the principle of the ‘pinch’ effect.
PART – B
Answer any FOUR questions
(4 x 7.5 = 30)
11. Derive expressions for the reflection and the transmission Coefficients for normal
incidence of a plane em wave at the boundary between two linear media.
12. An in finite straight wire carriers the current
0, for t  0
I(t) =
.
Io, for t > 0
Find the resulting electric field.
-213. a) Prove that the charge density transforms like the time component of the
4 – vector.
(2)
b) Obtain an expression for the relativistic Lagrangian for a charged particle.
(5.5)
14. Assuming a sinusoidal time dependence for the em fields inside a cylindrical
wave guides establish the Maxwells equations in terms of transverse and parallel
components.
15. Use the necessary em equation’s to explain the role played by the ‘magnetic
Reynolds number’ to distinguish between the diffusion of magnetic lines of force
and the freezing – in of the magnetic lines of force.
PART – C
Answer any FOUR questions
(4 x 12.5 = 50)
16. Explain the dispersion phenomenon in nonconductors and hence obtain the
Cauchy’s equation.
17. Derive expressions for the electric and magnetic fields of an oscillating electric
dipole.
18. Write down the field-strength tensors explicitly in matrix form and establish the
covariance of the Maxwell’s equations
19. Discuss the propagation of TE Waves in a rectangular wave guide with inner
dimensions a, b (with a = 2b) and find the frequencies of the first four modes.
20. Discuss the magneto hydrodynamic flow between boundaries with crossed
electric and magnetic fields and bring out the role played by the Hartmann
number.
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