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# BITSAT A beam of completely unpolarized light of intensity I is made to pass through a polarizer followed by an analyzer

What should be the angle between the axes of the polarizer, so that the intensity of the beam coming out of analyzer is 3/8 I

1. 45 degree

2. 30 degree

3. 60 degree

4. cos-1(3/8) rad

Answers (1)
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When unpolarized light is passed through the polarizer the intensity becomes half, Hence after passing through polarizer equals $\frac{I}{2}$

Now after coming out of the analyzer, the intensity becomes $\frac{3I}{8}$

Use Malus Law, $\frac{3I}{8} = \frac{I}{2}\cos ^{2}\Theta$

$\cos ^{2}\Theta = \frac{3}{4}$

$\Theta = 30^{0}$

Option (2) is correct.

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