Q. Two polaroids are kept crossed to each other. Now one of them us rotated through an angle of $45{^\circ}$. The percentage of incident light now transmitted through the system is
A) 15%
B) 25%
C) 50%
D) 60%
Explanation
(b) If $I_{0}$ is intensity of unpolarized light, then intensity of polarized light from 1st Polaroid=$I_{0}/2$.
On rotating through $45{^\circ}$, intensity of light from 2nd Polaroid,
$I = \left( \frac{I_{0}}{2} \right)\left( \cos{45{^\circ}} \right)^{2} = \frac{I_{0}}{2}\left( \frac{1}{\sqrt{2}} \right)^{2} = \frac{I_{0}}{4}$
$= 25\%\ I_{0}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.