What is the principle of Malus' law?

Malus' law states that the intensity of polarised light passing through a polariser varies with the angle of the polariser.

When unpolarised light passes through a polariser, only the component of the light that is parallel to the polarisation axis is transmitted. The intensity of the transmitted light is directly proportional to the square of the cosine of the angle between the polarisation axis and the direction of the incident light. This is known as Malus' law.

Mathematically, Malus' law can be expressed as I = I0 cos^2θ, where I is the intensity of the transmitted light, I0 is the intensity of the incident light, and θ is the angle between the polarisation axis and the direction of the incident light.

Malus' law is important in the study of polarisation and is used in a variety of applications, such as in the design of polarising filters for cameras and LCD screens. It also has applications in the field of optics, where it is used to determine the polarisation state of light and to measure the birefringence of materials.

Overall, Malus' law is a fundamental principle in the study of polarisation and has important applications in a variety of fields.