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Unpolarised light of intensity I passes ...

Unpolarised light of intensity I passes through an ideal polariser A. Another identical polariser B is placed behind A. The intensity of light beyond B is found to be `(I)/(2)`. Now another identical polariser C is placed between A and B. The intensity beyond B is now found to be `(I)/(8)` . the angle between polariser A and C is

A

`45^(@)`

B

`60^(@)`

C

`0^(@)`

D

`30^(@)`

Text Solution

Verified by Experts

The intensity of unpolarised light after passing through polariser A `= (I)/(2)` . Since the intensity of light does not change after passing through B, so the optice axes of polarisers A and B are parallel.
Let the angle between optic axes of polarisers A and C be `theta`. Then the angle between the optic axes of polarisers B and C is also `theta`.
Applying Malus' law.
`(I)/(8) = ((1)/(2) xx cos^(2) theta) xx cos^(2) theta " "or, cos^(2)theta = (1)/(2)`
or, `theta = 45^(@)`
The option A is correct.
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