M.Sc. (Semester II) (CBCS) Examination Mar/Apr-2018
Physics (Materials Science)
ELECTRODYNAMICS
Time: 2½ Hours
Max. Marks: 70
Instructions: Q.1 and Q.2 are compulsory. Attempt any three questions from Q. 3 to 7. All questions carry equal marks. Use of Non programmable calculator is allowed.
Q.1

Select correct alternatives:
06
Electric field intensity at any point in an electric field is equal to
Potential gradient
(Potential gradient)2
(potential gradient)y2
None of the above
The unit of electric flux density is
Coulomb
Farad meter
Coulomb (meter)2
Weber (meter)2
In electromagnetic wave, the phase difference between electric and magnetic field vectors E and B is
0



Magnetic vector potential due to magnetic dipole is proportional to
r
1r
1r2
1r3
Larmor formula for the power radiated by a non-relativistically accelerated charged particle is given by
14πε0 23 e2a2c3
23 e2a2c3
14πε0 23 e2ac2
14πε0 23 e2a2c2
When angle of incidence is greater than Brewster‟s angle, the reflected ray suffers a phase change of


0


State True or False
08
A monochromatic electromagnetic waves that the field strength at a point varies with time according to sine or cosine function.
A free electron (placed in the path of a plane electromagnetic wave) will start moving along the magnetic field.
For good conductors, skin depth varies inversely with half power of frequency.
A plane-polarized monochromatic electromagnetic wave incident on a plane interface at the Brewster angle gives rise to a unpolarized reflected wave.
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SLR-UN-476
The direction of propagation of electromagnetic wave is E. B .
For the case of a particle moving under attractive central force field, the angular momentum is no more constant but changes due to radiation reaction.
The equation of continuity is ∇.J −∂ρ∂t=0
In isotropic non-conducting media, the speed of electromagnetic wave is less than that of free space.
Q.2
Answer the following:
14
State the boundary conditions for an electrostatic field E.
05
How the Maxwell corrected Ampere‟s law? What is the physical significance of displacement current?
05
A long wire carries a current of uniform density. If i be the total current carried by the wire show that the magnetic energy per unit length stored within the wire is μ0i232π.
04
Q.3
Obtain the expression for magnetic vector potential A r in terms of a volume current Jb ×M and a surface current Kb ×n .
10
Find the magnetic field of a uniformly magnetized sphere.
04
Q.4
Discuss the "Reflection and Transmission at oblique Incidence" and obtain the Fresnel‟s equations for the case of polarization in the plane of incidence.
10
What are the phenomena of "Total Internal Reflection"?
04
Q.5
What is Thomson scattering? Show that this scattering is independent of the frequency and wavelength of incident beam.
10
If the incident radiation is plane polarized then find the total scattering cross section What is the dimension of LT?
04
Q.6
Four charges are arranged as shown in the adjacent Figure. Calculate the monopole moment, dipole moment and quadrupole moment of the system. Hence calculate the electric field E at point located at a distance from the center of configuration.
10
If at a point on boundary between two dielectric, the electric field make angles θ1 and θ2 with the normal in media of permittivity ∈1 and ∈2 respectively then show that tanθ1tan θ2=∈1∈2.
04
Q.7
What are the Gauge transformations? Explain the Coulomb Gauge and Lorentz Gauge.
10
What are the Faraday‟s law of electromagnetic induction and law?