Q 12-10-075JEE MainJEE Main 2023 (29 Jan, Shift 1)Medium
As shown in figures, three identical polaroids $P_1$, $P_2$ and $P_3$ are placed one after another. The pass axis of $P_2$ and $P_3$ are inclined at angle of $60^\circ$ and $90^\circ$ with respect to axis of $P_1$. The source $S$ has an intensity of $256\ \text{W m}^{-2}$. The intensity of light at point $O$ is ______ $\text{W m}^{-2}$.
Numerical value type. Enter your answer.
Answer: 24
Unpolarised light through $P_1$: $I_1=\dfrac{256}{2}=128\ \text{W m}^{-2}$.
Through $P_2$ (at $60^\circ$ to $P_1$): $I_2=128\cos^2 60^\circ=32\ \text{W m}^{-2}$.
$P_3$ is at $90^\circ-60^\circ=30^\circ$ to $P_2$: $I_3=32\cos^2 30^\circ=32\times\dfrac34=24\ \text{W m}^{-2}$.
Solution by Sreeraj P, M.Sc Physics