Question

Unpolarised light falls on two polarising sheets place one on top of other. If the intensity of transmitted light is one-fourth of the incident light, the angle between them is $P \pi rad$. Find the value of $P$.

Answer 1

From Malus's law, $I = I _{0} \cos ^{2} \theta$
$\Rightarrow \frac{I_{0}}{4}=I_{0} \cos ^{2} \theta$
$\therefore \frac{1}{4}=\cos ^{2} \theta$
$\Rightarrow \cos \theta=\frac{1}{2}$
$\Rightarrow \theta=\cos ^{-1}\left(\frac{1}{2}\right)=\frac{\pi}{3} rad$
$=0.33 \pi rad$
$\therefore P=0.33$