Question

Two Polaroids $P_1$ and $P_2$ are placed with their pass axes perpendicular to each other.
UnPolarised light of intensity $I_0$ is incident on $P_1$. A third Polaroid $P_3$ is kept in between $P_1$ and $P_2$ such that its pass axis makes an angle of ${30}^0$ with that of $P_1$. Determine the intensity of light transmitted through $P_1,P_2$ and $P_3$:

Answer 1

After passing through $P_1$, the intensity of light becomes

$I_1=\frac{I_0}{2}$

As angle between $P_1$ and $P_3$ is ${45}^o$,

So after passing through it intensity become,

$I_3=I_1{\cos }^2\theta =\frac{I_0}{2}{\cos }^{2}45=\frac{I_0}{4}$

Now angle between $P_3$ and $P_2$ is ${45}^o$,

So after passing through it intensity become,

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