What is Polarization?
{{Unreferenced section|date=March 2013}} '''Polarization''' (also polarisation) is a property of [[Transverse wave|transverse waves]]. Some waves have motion in another direction as well as the direction of the wave. In water, for instance, the wave will move across the water, but the wave will also move water up and down on the surface. [[Light wave]]s are similarly [[transverse wave]]s though they are also [[Photon|particles]]. [[Sound wave]]s do not have polarization, since they are [[longitudinal wave]]s. [[Polarized sunglasses]] take advantage of these oscillations. == Light == [[Image:Mudflats-polariser.jpg|right|thumb|400px|Effect of a polarizer on reflection from mud flats. In the picture on the left, the polarizer is rotated to transmit the reflections as well as possible; by rotating the polarizer by 90° (picture on the right) almost all [[specular reflection|specularly reflected]] sunlight is blocked.]] [[Image:CircularPolarizer.jpg|right|thumb|400px|The effects of a [[Polarizing filter (Photography)|polarizing filter]] on the sky in a photograph. The picture on the right uses the filter.]] Light reflected by shiny transparent materials is partly or fully polarized, except when the light is perpendicular to the surface. Polarization was first discovered in 1808 by the mathematician [[:en:Étienne-Louis_Malus|Etienne Louis Malus]]. A polarizing filter, such as a pair of polarizing [[sunglasses]], can be used to observe this effect by rotating the filter while looking through it at the reflection off of a distant horizontal surface. At certain rotation angles, the reflected light will be reduced or eliminated. Polarizing filters remove light polarized at 90° to the filter's polarization axis. If two polarizers are placed atop one another at 90° angles to one another, very little light can pass through both. Polarization by scattering is observed as light passes through the [[earth's atmosphere|atmosphere]]. The [[Rayleigh scattering|scattered]] light produces the brightness and color in clear [[sky|s