Polarized light is light in which the (electric and magnetic field) vibrations are confined to certain directions. Ordinary light vibrates in all directions perpendicular to the direction of propagation. Three types of polarized light are recognized: plane polarized, circular polarized, and elliptical polarized.
In plane polarized light, the vibrations are confined to a single plane. Plane polarized light can be used to distinguish between the two forms of chiral molecules (see chirality). Polarized ultraviolet radiation can influence chemical reactions that normally produce both left- and right-handed forms of a molecule, so that a preponderance of molecules of a particular handedness results. Plane polarized light can be produced by reflection, as from a sheet of glass on a water surface, or by passing through certain crystals, such as quartz, tourmaline, or calcite. Polarizing sunglasses use a Polaroid material to reduce glare by cutting out light polarized by reflection.
In circular polarized light, the plane of vibration continuously rotates.
See also Faraday rotation.