Q. Unpolarized light of intensity Io is incident on a stack of 2 polarizers, and intensity I emerges from the last polarizer. If the angle between the polarizers is 45 degrees, what is the ratio I/Io?

A 0.707
B 0.500
C 0.866
D 0.250
E 0.354

Thanks in advance

Malus' law is



where is the angle of rotation of the plane of polarization. One can rearrange the equation by dividing both sides by zero to get



If the angle, is 45 degrees, the problem becomes trivial:

and

so



So, your answer is B