Editing Polarization (waves) (section)

=== Polarized sunglasses ===
[[File:Mudflats-polariser.jpg|right|thumb|upright=1.5|Effect of a polarizer on reflection from mud flats. In the picture on the left, the horizontally oriented polarizer preferentially transmits those reflections; rotating the polarizer by 90° (right) as one would view using polarized sunglasses blocks almost all [[specular reflection|specularly reflected]] sunlight.]]
[[File:Test for polarized and non-polarized sunglasses 2.jpg|left|thumb|One can test whether sunglasses are polarized by looking through two pairs, with one perpendicular to the other. If both are polarized, all light will be blocked.]]
Unpolarized light, after being reflected by a specular (shiny) surface, generally obtains a degree of polarization. This phenomenon was observed in the early 1800s by the mathematician [[Étienne-Louis Malus]], after whom [[Malus's law]] is named. Polarizing [[sunglasses]] exploit this effect to reduce glare from reflections by horizontal surfaces, notably the road ahead viewed at a grazing angle.

Wearers of polarized sunglasses will occasionally observe inadvertent polarization effects such as color-dependent birefringent effects, for example in [[toughened glass]] (e.g., car windows) or items made from transparent [[plastic]]s, in conjunction with natural polarization by reflection or scattering. The polarized light from LCD monitors (see below) is extremely conspicuous when these are worn.