Question

Unpolarized light is passed through two polarizers that are oriented with their transmission axes perpendicular. What percentage of the light intensity passed by the first polarizer is the light intensity passed by the second polarizer when the second polarizer is rotated through 30°?

Answer 1

The angle formed by the two polarizers' transmission axes when the second polarizer is rotated by 30° is θ = 90° − 30° = 60°.

Let the intensities of light after passing through the first and second polarizers be I₁ and I₂, respectively.

By Malus’s law, I₂ = I₁ cos² θ

∴ I₂ = I₁ (cos 60°)²

= `I_1 (1/2)^2`

= `1/4`

= I₁ = 25 % of I₁