JEE Mains · Physics · STD 12 - 10. Wave optics
A source of light is placed in front of a screen. Intensity of light on the screen is \(I.\) Two Polaroids \({P}_{1}\) and \({P}_{2}\) are so placed in between the source of light and screen that the intensity of light on screen is \({I} / 2 .\) \({P}_{2}\) should be rotated by an angle of ........ (degrees) so that the intensity of light on the screen becomes \(\frac{3 I}{8}.\)
- A \(60\)
- B \(30\)
- C \(45\)
- D \(90\)
Answer & Solution
Correct Answer
(B) \(30\)
Step-by-step Solution
Detailed explanation
\(I=\frac{I_{0}}{2} \cos ^{2} \phi\) \(\frac{I}{2} \cos ^{2} \phi=\frac{3 I}{8}\) \(\cos ^{2} \phi=\frac{3}{4}\) \(\cos ^{2} \phi=\frac{\sqrt{3}}{2}\) \(\Rightarrow \phi=30\)
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