Bharathiar University 2000 M.Sc Physics Electromagnetic Theory and Electrodynamics - Question Paper
Degree
Reg. No. i. *
(For the candidates admitted during 1998 only) 1?
M*Sc. DIGEES 1XAMIMATION, N0IMB1S 2000, .,J ? % . , Second Semester
'Or
" di III Fliysics . J?
a o*um ,
i Paper VI ELECTROMACaiETIC THEORY AND ~
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' Time; Three hours . Masmxm: 100 marks-,.. i' ,
Jjz Answer ALL questions.
SECTION ACIO x 2 20 narks) ,, 5, _ ' .
1. The relation concectiz
(a) P - B + D (b) P * SqE + D " >
*>
r \ 3
371
{C)'5Sl(_I (d)
N
(c) Z> = %l + P (d) I * 5 + P. ' $
The ClaussiusMosotti formula h a * ~,.
fit+n ' 3
J m
/ Il3k 1}
(K-l) N (K-l)l
{k+2} . a%(r+2>;
3. The equation of continuity is
of oi
(c) , (<D V-J.= -~.
OT 31
4. The relation competing V and A is
(a) i = VV-i (b) l = -VF+~
<l St
(c) -VV-M. (d) = 7F+M.
oi ' cw
5. Maxwell's equations are valid under aB conditions except one and that is that they do not
(a) Apply to non-linear media
(b) Apply to non*-isvtropic media lc) Apply to noii-homogeaeotis media
(d) Apply to media which move with respect to system of coordinates.
6. [i je has the dimensions of
(a) An inductance (b) A capacitance
(c) An impedance (d) An electric field.
7, An~array in which, the maximum field direction is along the array is,
(a) Broadside array (b) End fire arraf
(c) Yagi antennas () Xp mMmms,
8. Hie region of anomalous dispersion coincides with the region of
(a) Mmmum absorption-
(b) Minimum amplitude
(c) Maximum absorption.
(d) Maximum reflection,
9, The Lorentz force law in reiatmstic notation is given by
(a(b) KrivP
(c) Fp , (d) K* t=qr}vFv,
10. The Lorentz gauge condition is
(a) ?xl = ~r~ (b) VxA=~ .
oi Bjx dt
(c) V * A = ~s p. (d) .
dt , ' fi Bt
3 166
SECTION B (5 x 4 = 20 marks)
11. (a) Obtain the expression for fee external field of a dielectric medium.
Or
(b) Write a note m the volume forces in the electrostatic field.
12. (a) Derive the equation of continuity.
Or
vv a brief note oa antenna arrays,
13. (a) Explain propagation of EM waves in free space.
Or
(b) Explain Brewsters law and degrees of polarisation.
14. , (a) Define duxerential scattering cross-section
jina total scattering cross-section.
Or
(b) Explain coherence and incoherence in
scattered light.
15. (a) Write down the covariance and tensor form of Maxwells equations. -
Or
Cb) Explain the covariance of electro-magnetic field tensor.
SECTION C (5 x 8 = 40 marks)
16. (a) Derive expressions for the potential and field due to a polarised sphere.
Or
(b) State and prove Thomson's theorem.
17. (a) Derive Maxwell's equations in electromagnetic potentials.
Or
(b) Derive expressions for the electric and magnetic field components in the near and far zones due
to an oscillating electric dipole,
18. (a) Discuss the propagation of plane EM waves in
(i) isotropic dielectric and
(ii) anisotropic dielectric.
. ' ' ~ Or
(b) Explain reflection froa a metallic surface. Write a note on cavity resonator.
19. (a) Discuss normal dispersion in liquids and solids. , ,
Or
(b> Give a detailed account of scattering by a tree electron and obtain the - Thomson scattering cross section formula.
5 166
20. (a) Obtain the transformation relations for charge and current densities. ' '
Gr:
(b) Derive the covariant form of electric and
magnetic field equations. Arrive at the variant form of the Lorentz force law.
SECTION D (2 x 10 = 20 marks)
21. (a) Derive the Claxissixis-Mosoiti relation. Show how it was modified by Debye in the case of polar molecules.
Or
(b) Discuss the radiation produced by a low velocity accelerated charged particle. Derive Larmors
power formula and discuss the three cases.
. 22, (a) Derive the tquationa for the trrotjagatioh of EM waves la a rectangular waveguide. Obtain the expression for cutoff wavelength- . '
Or
(b) Discuss the theory of anomalous dispersion. Explain it in the case of solids. ,
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