Malus's Law describes the intensity of light ($I$) after passing through a second polarizer (analyzer): $I=I_{transmitted}{\cos }^2\theta$ where $I_{transmitted}$ is the intensity of the light incident on the analyzer (which is $I_0/2$ if the first light was unpolarized) and $\theta$ is the angle between the two polarizing axes.

• If $\theta =90^{\circ }$ (Crossed polarizers), $I=0$.