Question

With unpolarized light incident on a linear polarizer, you measure a power of 2 mW after the polarizer. A second polarizer is then inserted into the system, and you then measure 0.5 mW. What is the angle between the pass axes of the two polarizers? Does your answer depend on if the second polarizer is placed before or after the polarizer?

Answer 1

We have for polarisers, $I_2 = I_1 \cos^2 \theta$

Angle, $\theta =\cos^{-1} \sqrt{\frac{I_2}{I_1}} = \cos^{-1} \sqrt{\frac{0.5}{2}} = 60^0$

Irrespective; of the position of second polariser, the intensity will be same.