First slide

Polarisation

Question

Two Polaroids are kept crossed to each other. Now one of them is rotated through an angle of 45^o The percentage of incident light now transmitted through the system is

Moderate

A

15%
B

25%
C

50%
D

60%

Solution

According to Mal us law
$I = I_{m} \cos^{2} θ when light passes through polaroid, only 50 % light is able to pass i.e., I_{m} = I / 2 % of incident light transmitted = \frac{I / 2 \cos^{2} 45^{\circ}}{I} \times 100 = \frac{I / 4}{I} \times 100 = \frac{100}{4} = 25 %$

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