(a) Show, with the help of a diagram, how unpolarised sunlight gets polarised due to scattering. (b) Two polaroids P1 and P2 are placed with their pass axes perpendicular to each other. Unpolarised light of intensity I0 is incident on P1. A third Polaroid P3 is kept in between P1 and P2 such that its pass axis makes an angle of 45° with that of P1. Determine the intensity of light transmitted through P1, P2 and P3.

(a)Unpolarized light scattering from air molecules shakes their electrons perpendicular to the direction of the original ray. The scattered light therefore has a polarization perpendicular to the original direction and none parallel to the original direction. (b)Intensity of light is halved after passing through a polaroid. Hence, intensity of light transmitted through P1 is IP1 = I0/2. Axis of P3 makes an angle of 45° with the axis of P1. Also, axis of P1 and P2 are perpendicular to each other. Hence, angle between axis of P2 and P3 is 45°. After passing through P3, IP3 = IP1cos²(π/4) = I0/4. After passing through P2, IP2 = IP3cos²(π/4) = I0/8.