Question

Two Polaroids are placed into the unpolarized beam of a light source. The angle between
the axes of polarization of the two Polaroids is 30°. If the intensity of the incident beam is
Io, what is the intensity of the transmitted light?

Answer 1

The intensity of the transmitted light is given by the Malus's law:

$$I = I_0\cos^2\theta$$

where $I_0$ is the intensity of the incident beam and $\theta = 30\degree$ is the angle between the axes of polarization of the two Polaroids. Thus, obtain:

$$I = I_0\cos^2\theta = I_0\cos^230\degree = I_0 \left( \dfrac{\sqrt3}{2} \right)^2 = \dfrac{3}{4}I_0$$

Answer. $I = \dfrac{3}{4}I_0$.