Question

An unpolarized beam of light of intensity $I_0$ falls on a polaroid. The intensity of the emergent beam is,
$($Given average value of ${\cos }^2\theta =\frac{1}{2})$

• A. $\frac{I_0}{2}$
• B. $I_0$
• C. $\frac{I_0}{4}$
• D. zero

Answer 1

The correct option is A $\frac{I_0}{2}$

According to Malu's law, the intensity emerging from the polaroid is given by,
$I=I_0{\cos }^2\theta$
$\therefore I=I_0\times \frac{1}{2}=\frac{I_0}{2}$
[Here, we take average value of ${\cos }^2\theta =\frac{1}{2}$]

Hence, $\left(A\right)$ is the correct answer.