- The study of polarised light, which yields a wealth of information about the physical condition of objects which have transmitted or reflected it. Light which is reflected or scattered generally becomes polarised, like sunlight scattered in the Earth’s atmosphere. Cutting out this light is the principle of Polaroid sunglasses. The polarisation of light has been used to yield information about planetary surfaces which have reflected it or about interstellar dust which has scattered it.
- The measurement of the rotation of the plane of polarization of radiant energy, such as light, usually through the use of a polarimeter.