JEE MAIN - Physics (2023 - 29th January Morning Shift - No. 22)
As shown in the figure, 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 $$\frac{W}{m^2}$$. The intensity of light at point O is ____________ $$\frac{W}{m^2}$$.
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Answer
24
Explanation
By first polaroid P1 intensity will be halved then P2 and P3 will make intensity $\cos ^{2}\left(60^{\circ}\right)$ and $\cos ^{2}\left(30^{\circ}\right)$ times respectively.
Intensity out $=\frac{256}{2} \times \frac{1}{4} \times\left(\frac{\sqrt{3}}{2}\right)^{2}=\frac{256 \times 3}{2 \times 4 \times 4}=\mathbf{2 4}$
Intensity out $=\frac{256}{2} \times \frac{1}{4} \times\left(\frac{\sqrt{3}}{2}\right)^{2}=\frac{256 \times 3}{2 \times 4 \times 4}=\mathbf{2 4}$
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