As shown in figures, three identical polaroids , and are placed one after another. The pass axis of and are inclined at an angle of and with respect to axis of . The source S has an intensity of . The intensity of light at point O is _____ .

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Solution

Q.
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 an angle of $60 °$ and $90 °$ 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 _____ $\frac{W}{m^{2}}$ . [2023]

Ans.
(24)

By first polaroid $P_{1}$ intensity will be halved then $P_{2}$ and $P_{3}$ will make intensity $\cos^{2} 60 °$ and $\cos^{2} 30 °$ times respectively.

$Intensity out = \frac{256}{2} \times \frac{1}{4} \times {(\frac{\sqrt{3}}{2})}^{2} = \frac{256 \times 3}{2 \times 4 \times 4} = 24$

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