Faraday rotation is a phenomenon that occurs when polarized light passes through a magnetic field in a medium, such as a gas or a liquid. The magnetic field causes the plane of polarization of the light to rotate, which can be measured to determine the strength and direction of the magnetic field. This effect is named after the scientist Michael Faraday, who discovered it in the 19th century. Faraday rotation is used in various applications, including astronomy to study magnetic fields in space and in optical devices for improving communication technologies.