Bharathiar University 2002 M.Sc Physics Electromagnetic Theory and Electrodynamics - Question Paper
Degree
SECTION D (2 x 10 = 20 marks)
21. (a) Derive Langevin equation of Polaar-molecules.
Or
(b) Show that
(i) The momentum of charged particle in an
electromagnetic field is given by
P = mV + A
(ii) The Lagraagian function of the charged particle in m electromagnetic field is given by
L = mv2 -q(p ~V -A)
22, (a) Derive the Rayleighs resistnce formala for Strong SUL zzz*:.
Or . *
(b) Show that the scattering cross-section when plane monochromatic waves are incident on
im 23 58]
21S5
(For the candidates admitted from 1999 onwards)
M.Sc. DEGREE EXAMINATION, APRIL 2002.
Second Semester
Part III Physics
Parser VI - ELECTROMAGNETIC THEORY AND ELECTRODYNAMICS
Time: Three hours Maximum: 100 marks
Answer ALL questions.
SECTION A (10 x 2 20 marks)
Choose the correct answer: 11''
1, - Electrical susceptibility vades inversely with absolute temperature is called
r*
(a) Polarisation (b) Curie law
(c) Debye relation (d) Gauss law.
2, The units of Poyating vector is {) watt/a2 -' (b) mVsec (c) watt-ma (d) jottles.
3 Brewsters angle is sometimes called
(a) reflection coefficient
(b) transmissioE coefficient C#_.olarismgade .
(d) tla1 angle.
4, The valve of intrinsic impedance of free space is
S' ' (c) 737 ohms - (d) 377 ohms.
. 5 The Biot-Savait expression for the magnetic field
; camdvi&gehazgeis
<1. 4 r ~ 4*0
n
%
. (c;iM ,* /-i.
r3 4Mq r
Answer in 1 or 2 sentences : , x
I
8, What is meant by Cerenkov-radiation?
7, Mention the ro postulates of Special theory of
relativitv.
8, Mention the law of frequency of reflection .and refractiocu
9, Defia Poyntiuf T&ctor, j>7.
10 Define Electric potential. ' *
i
SECTION B (5 x 4 - 20 marks)
11. (a) Deduce the differential form of Gausss law for dielectrics.
Or
(b> Derive Gkusius-Mosotti equation.
12. (a) Show that the charge density in a conductor obeys the equation
cr . , dq _0
wmiiii ji <>kW(irnii> S5 y
(b) Meatioa the Maxwell's equations,
18. (a) A plane electromagnetic wave trawls through a uniform plasma. Calculating the Pointing vector, show that it vanishes if the frequency of the wave is equal to the plasa*a frequency.
Or
.(b) Mention, the expression for skin depth and find the same for good conductors,
14 (a) Define the differential and total scattering cross-section.
Or
(b) Calculate the. value and dimension of Thomson Scattering cross-section.
3 ' 2185
%
15, (a) Prow the 'E.B. is invariant under Lorentz traBaformation,
Or
, (b) Show that the self product of electromagnetic field tensor is given, by
P =2
18, (a) Show that the field inside a uniformly
polarised sphere is constant every where and
times the density of polarisation and is directed opposite to the direction of polarisation.
Or
{b) Deduce Debye relation of study of molecular structure.
If, (a) Starting from Maxwells equation, prove the Coulomb's law and Continuity equation.
Or
(b) Express the Lorentz force formula in terms of electromagnetic potentials.
18, (a) Derive the equations of Telegraphy.
Or
(b) Derive a standard wme equation representing unattenuated wave travelling at a speed v.
13. (a) Derive as expression for the classical radius of the electron.
Or
(b) What is normal and anomalous dispersion? Derive Sellmeiers equation for the refractive index of a dielectric medium.
20. (a) Prove tlat the space interval j:2?2 + is not invariant under Lorentz transformation while the space-time interval x% + ys + z3 - cV is invariant.
Or
(b) Writing Maxwells equations in 4-vector form, prove that they are invariant under Lorentz transformation.
5 2185
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| Earning: Approval pending. |
