**Malus' law** gives the transmitted intensity through a second polarizer as:
- $I = I_0 \sin\theta$
- $I = I_0 \cos^2\theta$
- $I = I_0 \sin^2\theta$
- $I = I_0$
Show answer and solution
Correct answer: B. $I = I_0 \cos^2\theta$
When plane-polarized light (intensity $I_0$) hits a polarizer whose axis makes angle $\theta$ with its polarization, the transmitted intensity is $I_0 \cos^2\theta$.
At $\theta = 0$, full intensity
at $\theta = 90°$, zero (crossed polarizers).