Question

Two Polaroids $P_1$ and $P_2$ are placed with their axis perpendicular to each other. Unpolarized light $l_0$ 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 $P_1$. The intensity of transmitted light through $P_2$ is

• A. $\frac{I_0}{2}$
• B. $\frac{I_0}{4}$
• C. $\frac{I_0}{8}$
• D. $\frac{I_0}{16}$

Answer 1

The correct option is C $\frac{I_0}{8}$

$I=I_0.{\cos }^2\theta$

$\theta =$ angle made by $E$ vector with transmission axis.wherein

$I=$ Intensity of transmitted light after polarisation.

$I_0=$Intensity of incident light.

Intensity of light after crossing $P_1=\frac{I_0}{2}$

Intensity of light after crossing $P_3=\frac{I_0}{2}.{\cos }^2{45}^o=\frac{I_0}{4}$

Intensity of light after crossing $P_2=\frac{I_0}{4}.{\cos }^2{45}^o$

$I=\frac{I_0}{8}$