Question

A polarizer-analyzer set is adjusted such that the intensity of light coming out of the analyzer is just 10 % of the original intensity. Assuming that the polarizer-analyzer set does not absorb any light, the angle by which the analyser need to be rotated further to reduce the output intensity to be zero is

1. a. 45^o
2. b. 90^o
3. c. 71.6^o
4. d. 18.4^o

Answer 1

Correct Answer is option D } 18^o

Intensity after polarisation through polaroid = I_ocos²φ

So, 0.1I_o = I_ocos²φ

⇒cosφ = √0.1

⇒cosφ = 0.316

Since, cos φ < cos 45^o therefore, φ > 45^o If the light is passing at 90^o from the plane of polaroid, than its intensity will be zero.

Then, θ = 90^o − φ therefore, θ will be less than 45^o. So, the only option matching is option d which is 18.4^o