Polarization of Light

Light, viewed classically, is a transverse electromagnetic wave. Namely, the underlying oscillation (in this case oscillating electric and magnetic fields) is along directions perpendicular to the direction of propagation. This is in contrast to longitudinal waves, such as sound waves, in which the oscillation is confined to the direction of propagation. Light is said to be linearly polarized if its oscillation is confined to one direction (the direction of the oscillation of the electric field is defined as the direction of polarization). Most light sources in nature emit unpolarized light i.e., light consists of many wave trains whose directions of oscillation are completely random. Light may be polarized by passing it through a sheet of commercial material called Polaroid, invented by E.H. Land in 1938. A sheet of Polaroid transmits only the component of light polarized along a particular direction and absorbs the component perpendicular to that direction. Consider a light beam in the z direction incident on a Polaroid which has its transmission axis in the y direction. On the average, half of the incident light has its polarization axis in the y direction and half in the x direction. Thus half the intensity is transmitted, and the transmitted light is linearly polarized in the y direction.

3D animations explaining circularly polarized, linearly polarized, and unpolarized electromagnetic waves.