Question

Unpolarised light rays of intensity $\textit{I}_{0}$ is passed through a polaroid $\textit{A}$ and then through another polaroid $\textit{B}$ which is oriented in such a way that its principal plane makes an angle of $\text{45}^{\text{o}}$ relative to that of $\textit{A}$ . What will be the intensity of the emergent light?

• A. $\frac{\textit{I}_{0}}{4}$
• B. $\frac{\textit{I}_{0}}{8}$
• C. $\textit{I}_{0}$
• D. $\frac{\textit{I}_{0}}{2}$

Answer 1

Answer: (A)

Relation between intensities is

When unpolarised light passes the polaroid, intensity become half.
$I_{A}=\frac{I_{o}}{2}$
$\left(\text{I}\right)_{B}=I_{A}\left(\text{ cos}\right)^{2}\left(\left(\text{45}\right)^{\text{o}}\right)\left(\text{I}\right)_{B}=\left(\frac{\left(\text{I}\right)_{0}}{2}\right)\left(\text{ cos}\right)^{2}\left(\left(\text{45}\right)^{\text{o}}\right)=\frac{\left(\text{I}\right)_{0}}{2}\times \frac{1}{2}=\frac{\left(\text{I}\right)_{0}}{4}$