Question

Unpolarized light with intensity I₀ is incident on two polaroids. The axis of the first polaroid makes on the angle of 50° with the vertical, and the axis of the second polaroid is horizontal. What is the intensity of the light after it has passed through the second polaroid?

Answer 1

According to Malus' law, when the unpolarized light with intensity l₀ is incident on the first polarizer, the polarizer polarizes this incident light. The intensity of light becomes I₁ = I₀/2.

Now, I₂ = I₁ cos²θ

∴ I₂ = `("l"_0/2) cos^2 (theta_2 - theta_1)`

`= ("l"_0/2) cos^2 (90° - 50°)`

∴ I₂ = `("l"_0/2) cos^2 40°`

The intensity of light after it has passed through the second polaroid `("l"_0/2) cos^2 40° = "I"_0/2 (0.76660)^2`

= 0.2934 I₀