Difference between using 2 and 3 polarizer

Question

Is there a difference in using 2, 3 or more polarizer? Is there anything that 3 polarizer can do but not 2 polarizer cannot?

Answer 1

There is a famous undergraduate experiment that involves 2 and 3 polarizers and yields different results based on this. It consists of a light source, 2 polarizers at specific angles and a detector.

If both polarizers are parallel, light passes through and can be detected. If they are perpendicular to each other, all of the light is blocked and nothing is detected.

Finally, if a third polarizing filter is included between the perpendicular filters and placed at a 45° angle, some light can again pass through.