Malus's law

Malus's Law describes how the intensity of light changes when it passes through a polarizing filter. Specifically, it states that when polarized light hits a second polarizer, the amount of light that passes through depends on the angle between the light's polarization direction and the filter's axis. If the light is perfectly aligned with the filter, it passes through completely. If it’s at a right angle, none gets through. Mathematically, the transmitted light intensity is given by the square of the cosine of the angle between the two polarization directions. This principle underlies many optical devices and technologies.