Q 12-10-002NEETNEET 2025Top questionMedium
The intensity of transmitted light when a polaroid sheet, placed between two crossed polaroids at $22.5°$ from the polarization axis of one of the polaroid, is ($I_0$ is the intensity of polarised light after passing through the first polaroid):
Answer: (C) $\dfrac{I_0}{8}$
The middle sheet is at $22.5°$ to the first polaroid, so it is at $90° - 22.5° = 67.5°$ to the second (crossed) polaroid. By Malus's law:
$$I = I_0\cos^2 22.5°\cos^2 67.5° = I_0(\cos 22.5°\sin 22.5°)^2 = I_0\left(\frac{\sin 45°}{2}\right)^2 = I_0 \times \frac{1}{8}$$
Solution by Sreeraj P, M.Sc Physics