Q 12-10-116JEE MainJEE Main 2021 (26 Aug, Shift 2)Easy
A source of light is placed in front of a screen. The intensity of light on the screen is $I$. Two Polaroids $P_1$ and $P_2$ are so placed in between the source of light and screen that the intensity of light on the screen is $\frac{I}{2}$. Then the $P_2$, should be rotated by an angle of (degrees) so that the intensity of light on the screen becomes $\frac{3I}{8}$.
Numerical value type. Enter your answer.
Answer: 30
After $P_1$ the intensity is $\frac{I}{2}$. Since the screen still receives $\frac{I}{2}$, $P_2$ is parallel to $P_1$.
To get $\frac{3I}{8}$: $\dfrac{I}{2}\cos^2\theta = \dfrac{3I}{8} \Rightarrow \cos^2\theta = \dfrac{3}{4} \Rightarrow \theta = 30^\circ$.
Solution by Sreeraj P, M.Sc Physics