Question

Two Polaroids $P_1$ and $P_2$ are placed with their axis perpendicular to each other. Unpolarised light $I_0$ is incident on $P_1$. A third polaroid $P_3$ is kept in between $P_1$ and $P_2$ such that its axis makes an angle $45^{\circ }$ with that of $P_1$. Then intensity of transmitted light through $P_2$ is $\frac{I_0}{n}$. Find $n$.

Answer 1

Answer: 8

$I_1=\frac{I_0}{2}$
$I_2=\frac{I_0}{2}{\cos }^{2}45^{\circ }=\frac{I_0}{4}$
$I_3=\frac{I_0}{4}{\cos }^{2}45^{\circ }=\frac{I_0}{8}$