Two polarizers have their transmission axes at an angle θ. Unpolarized light of intensity I is incident on the first polarizer. What is the intensity of the light transmitted by the second polarizer? A) I cos²θ B) 0.5I cos² θ C) 0.25I cos² θ D) I cos θ E) 0.25I cos θ

Question

Quizplus · Accepted Answer

The intensity of the light transmitted by the first polarizer is Icos²θ (Malus' law). The transmitted light is then incident on the second polarizer, so the intensity of the light transmitted by both polarizers is Icos²θcos²θ=Icos⁴θ. Therefore, the intensity of the light transmitted by the second polarizer is (1/2)Icos⁴θ (since the original intensity I is divided equally between the two polarizers). Simplifying this expression, we get 0.5Icos²θ(1+cos²θ)=0.5Icos²θ(1+cos²θ)=0.5Icos²θ²θ, which is the same as choice B.

Two Polarizers Have Their Transmission Axes at an Angle θ