Question

A beam of unpolarized light of intensity $I_0$ is passed through a polaroid $A$ and then through another polaroid $B$. Polaroid $B$ is oriented so that its principal plane makes an angle of ${45}^{\circ }$ relative to that of $A$. The intensity of the emergent light is,

• A. $I_0$
• B. $I_0/2$
• C. $I_0/4$
• D. $I_0/8$

Answer 1

The correct option is C $I_0/4$

The situation is as shown below.


The intensity of light coming out of polaroid $A$ is $\frac{I_0}{2}$ and this intensity is incident on polaroid $B$

According to Malu's law, for polaroid $B$,
$I=\left(\frac{I_0}{2}\right){\cos }^2\left({45}^{\circ }\right)=\frac{I_0}{2}\times \frac{1}{2}=\frac{I_0}{4}$

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