An interaction between a polarized electromagnetic pulse, such as a beam of light, and a magnetic field, in which the plane of polarization is rotated in proportion to the intensity of the component of the magnetic field in the direction of travel of the pulse
In physics, the Faraday effect or Faraday rotation is a magneto-optical phenomenon, or an interaction between light and a magnetic field. The rotation of the plane of polarization is proportional to the intensity of the component of the magnetic field in the direction of the beam of light