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EEJ MAIN Physics QUESTION #7043
Question 1
Unpolarised light with intensity $I_0$ passes through polaroid A, then through polaroid B. If the transmission axis of B is at $45^\circ$ to A, find the final intensity.
  • $I_0$
  • $\frac{I_0}{2}$
  • $\frac{I_0}{4}$✔️
  • $\frac{I_0}{8}$
Correct Answer Explanation

After passing through polaroid A, the intensity becomes $I_1 = \frac{I_0}{2}$.

According to Malus's Law, after passing through polaroid B:

$I_2 = I_1 \cos^2 \theta = \frac{I_0}{2} \cos^2(45^\circ) = \frac{I_0}{2} \times \left( \frac{1}{\sqrt{2}} \right)^2 = \frac{I_0}{4}$.