### JEE Main On 08 April 2018 Question 8

##### Question: Unpolarized light of intensity I passes through an ideal polarizer A. Another identical polarizer B is placed behind A. The intensity of light beyond B is found to be $ \frac{I}{2} $ . Now another identical polarizer C is placed between A and B. The intensity beyond B is now found to be $ \frac{I}{8} $ . The angle between polarizer A and C is: [JEE Main Online 08-04-2018]

#### Options:

A) $ 45{}^\circ $

B) $ 60{}^\circ $

C) $ 0{}^\circ $

D) $ 30{}^\circ $

## Show Answer

#### Answer:

Correct Answer: A

#### Solution:

- Polarizing axis of A & B polarizer are parallel to each other $ {I_1}\text{=}\frac{I}{2}co{s^{2}}\theta $

$ \frac{I}{8}=I _1{{\cos }^{2}}\theta $

$ \frac{I}{8}=\frac{I}{2}{{\cos }^{4}}\theta $

$ \cos \theta =\frac{1}{\sqrt{2}} $