Polarisation

Polarisation describes when waves previously vibrating at more than one angle and more than one plane, are reduced to a single plane. The phenomenon was first discovered by Augustin-Jean Fresnel.

History
In 1817, Augustin-Jean Fresnel and François Arago began their experiments on polarisation. The theory that light travels in waves was backed up in 1816 by a series of precise experiments with diffraction - the way light splits around objects into shadows - by Fresnel, a french engineer.

Concept
Fresnel worked out that light moves forward in waves that vibrate transversely - perpendicularly to the direction in which they are travelling. Ordinary light vibrates at every angle or plane, but when it is polarised - by passing through a polarising filter - the vibrations are reduced to a single plane.