A clear sheet of polaroid is placed on the top of similar sheet so that their axes make an angle sin−1⁡35 with each other. The ratio of intensity of the emergent light to that of unpolarised incident light is

If I is the intensity of the incident unpolarised light, the intensity transmitted by the first is I2. This is the intensity of incident light on the second polaroid. Intensity transmitted by the second polaroid is 12cos2⁡ θ, where θ is the angle between the axes. Here sin ⁡θ=35,cos ⁡θ is therefore 45.12cos2 ⁡θ=12×452=825I825is the required ratio.