AP EAMCET201822 Apr 2018Morning ShiftPhysicsWave OpticsActual
Two polaroids are placed in the path of unpolarised light beam of intensity I₀ such that no light is emitted from the second polaroid. If a third polaroid whose polarisation axis makes an angle with that of the first polaroid is placed between the polaroids, then intensity of light emerging from the last polaroid is
Options
- A( I₀ 8 ) ^2 2
- B( I₀ 4 ) ^2 2
- C( I₀ 2 ) ^2
- DI₀ ^2
Correct answer
A. ( I₀ 8 ) ^2 2
Step-by-step solution
When unpolarised light passes through first polariser, it becomes polarised and its intensity becomes half. After first polariser, intensity I₁=I₀ / 2 After second polariser, intensity I₂= I₀ 2 ^2 (Malus law) After third polariser, intensity I₃= I₀ 2 ^2 ^2 (90^ - ) (because this is at 90^ angle from first polariser) I₃= I₀ 2 ^2 ^2 = I₀ 8 (2 )^2= I₀ 8 ^2 2