9. (a) What are dielectrics? Differentiate between polar and non-polar dielectrics with examples. (b) Find the relation between electronic polarizability and atomic radius. (c) Establish the relation = 0 + P, where the parameters have their usual meaning. (d) A potential of 10V is applied across a parallel plate capacitor having area of 6.45 x 10m and plate separation is 0.002m. If a material having dielectric constant of 6.0 is placed within the region between the plates calculate the amount of charge stored in the plate and the net amount of polarization. 10. (a) Write down the expression for intensity distribution of single slit diffraction and explain the symbol used. (b) Sketch how the intensity varies with angle of diffraction. (c) Find the values of the angle at which minima are located. (d) Find the condition that the angle satisfies in order to be the position of a secondary maximum. (e) Describe the fringe pattern when white light is incident on a plane transmission grating. (f) A light of wavelength 6 x 10-5 cm falls normally on a slit of width 0.2 mm. Calculate i) the total angular width of the central maximum ii) the linear width of central maximum on a screen placed 2 m away. 11. (a) Write down Maxwell's wave equations for free space with their physical significance. Hence prove that velocity of EM wave is equal to the velocity of light. (b) Write down the Maxwell's modification of Ampere's law. An electric wave is represented by E = Es cos(1000x5000r). Calculate the wavelength and speed of propagation of the wave. Show that the displacement current is negligible compared to (c) the conduction current at any frequency when the conductor is subjected to an alternating field. (d) A circular conducting disc of 5 cm radius maintains an angular motion of 1000 rpm with its plane perpendicular to the magnetic field. If due to this motion, the induced e. m. f. between the center and the edge of the disc is 3.22 mV, calculate the magnetic flux density.