Malus's Law describes how the intensity of polarized light changes when it passes through a polarizing filter. According to this law, the transmitted light intensity is proportional to the square of the cosine of the angle between the light's polarization direction and the filter's axis. This means that if the light is aligned with the filter, it passes through fully, while at 90 degrees, no light passes through. The law is named after the French physicist Étienne-Louis Malus, who discovered this relationship in 1809. Malus's Law is fundamental in optics and is used in various applications, including photography, sunglasses, and LCD screens, to control light intensity and reduce glare.