Question

If unpolarized light of intensity $I_0$ is incident on left polarizer and right polarizer is rotating at angular velocity $\omega$, then intensity of light emerging from right polarizer is

• A. $\frac{I_0}{2}(cos2\omega t+1)$
• B. $\frac{I_0}{4}(cos\omega t+1)$
• C. $\frac{I_0}{8}(cos2\omega t+1)$
• D. $\frac{I_0}{4}(cos2\omega t+1)$

Answer 1

The correct option is D $\frac{I_0}{4}(cos2\omega t+1)$

When unpolarized light passes through a polarizer, the intensity of the emerging polarized light is half of the incident intensity.
Therefore, light from left polarizer has intensity $I^{\prime }=\frac{I_0}{2}$.


After passing through right polarizer,
$I=\frac{I_0}{2}co{s}^2\theta =\frac{I_0}{2}\left(\frac{1+cos2\theta }{2}\right)$
$I=\frac{I_0}{4}(cos2\omega t+1)$