Question

1. Polarized filters are great for aligning light, but if you hold two filters oriented 90 to one another, light will not pass through. Now put a third polaroid filter between two such that it makes a 45-degree angle to each of the other two filters. Now, some light gets through – why?

Answer 1

Suppose the first polarizer is horizontal one and the second polarizer is vertical one. When an unpolarized light is incident on the first(horizontal) polarizer then the light will be horizontally polarized. After that when it falls on the second, it will completely block the light since it is vertical polarizer.

But if we place a third Polaroid in between these making an angle of 45°,it will allow half of the intensity from the first polarizer according to its polarizing axis of itself . Then the emergent light rays can be passed through the vertical because now it is not exactly horizontal or half of the photons does not have the 'memory ' that it is horizontally polarized.