Question

A single polarizer will stop _____ of the incoming light. less than 50% 50% more than 50% but less than 100% 100%

Answer 1

The answer is 50%. Remember, it's a single polarizer, not two of them.

Answer 2

So we want to know how much light will a single polarizer stop. Since the polarizer intensity formula is I=I0cos^2(a), where I is the intensity, I0 is the initial intensity and a is the angle of the light's initial polarization direction and the axis of the polarizer. Also, the average of cos^2a is 1/2 so I=(1/12)*I0. and I/I0=1/2 or 50%. So the light that passes trough one polarizer has 50% of the initial intensity. And the correct answer is 50%.