Electromagnetic Theory — DU B.Sc. (Hons) Physics Previous Year Question Papers

(c) For a light beam passing from air to glass (n = 1.5), find the angle of incidence at which reflection vanishes. (3) 5. (a) Discuss the propagation of EM waves in an anisotropi.c medium and define dielectric tensor. (b) Distinguish between plane, circular, and elliptically pol'arized light with sketches. (5) (c) A quartz plate of thickness 0.6 mm has refractive indices 1.553 and 1.544 for e-ap,d o-rays respectively. For which wavelength will it act as a quarter-wave plate? (3) 6. (a) Derive the eigenvalue equation for TE modes in a planar dielectric waveguide. (12) (b)~E.xplain phase and group velocities in guided 8o = 8.854 X 10-[2F/in and Lto = 47t x 10-7H/in Intrinsic impedance of free space: Ilo ~ 377 a Speed of light c = 1/JF;:; s 3 x 108 in/s . Attempt FIVE questions in all. (i) Write Maxwell's equations in differential form and mention the physical significance of each term. (ii) Define Coulomb and Lorentz gauges. What is the advantage of using Lorentz gauge in wave propagation problems? (iii) What are the conditions for a crystal plate to act a§ a quarter-wave and a half-wave plate. (iv) What is the difference between optical rotation and polarization rotation? (v) What is an extraordinary ray? In which crystal does it occur? (vi) A plane EM wave of frequency 1 GHz propagates in copper (a = 5.8X107 S/in, pr = Flo). Find the skin depth. (vii) The specific rotation of sugar solution is 66° din-1 (g cm-3)-I. A 10 cm tube produces a rotation of 13°. Find the concentration of the solution. 2. (a) Derive Poynting's theorem and interpret each term. (10) (c) Sunlight incident on Earth delivers about 1.3 kw/ m2. Find the amplitude of the electric and magnetic fields associated with sunlight. (3) 3. (a) Starting from Maxwell's equations, derive the electromagnetic wave equation in free space. (b) Prove that electromagnetic waves in vacuum are transverse in nature. (5) (c) An EM wave has E = 100 cos (27t x 108t -Pz) V/in in a medium with g = 4go, LL = Ilo. Find the wave velocity and intrinsic impedance. (5) 4. (a)State and derive Fresnel's forinulae for perpendicular polarization. (10) (b) Explain Brewster's angle and show how it can be used for po.1arization. (5)