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

Answer: 0.33

From Malus's law, $I=I_0{\cos }^2\theta$
$\Rightarrow \frac{I_0}{4}=I_0{\cos }^2\theta$
$\therefore \frac{1}{4}={\cos }^2\theta$
$\Rightarrow \cos \theta =\frac{1}{2}$
$\Rightarrow \theta ={\cos }^{-1}\left(\frac{1}{2}\right)=\frac{\pi }{3}rad$
$=0.33\pi rad$
$\therefore P=0.33$