Changes

[[Image:PrismAndLight.jpg|thumb|300px|A beam of white light (entering upwards from the right) is dispersed into its constituent colors by its passage through a [[triangular prism (optics)|prism]].  The fainter beam of white light exiting to the upper right has been reflected (without dispersion) off the first surface of the prism.]]

[[Image:PrismAndLight.jpg|thumb|300px|A beam of white light (entering upwards from the right) is dispersed into its constituent colors by its passage through a [[triangular prism (optics)|prism]].  The fainter beam of white light exiting to the upper right has been reflected (without dispersion) off the first surface of the prism.]]

'''Light''', or '''visible light''', is [[electromagnetic radiation]] of a [[wavelength]] that is visible to the human [[eye]] (about 400–700 [[nanometre|nm]]).  In a [[Science|scientific]] context, the word ''light'' is sometimes used to refer to the entire [[electromagnetic spectrum]].<ref>{{cite web | url = http://www.lightsources.org/cms/?pid=1000166 | title = What Is a Light Source?}}</ref> Light is composed of an [[elementary particle]] called a [[photon]].

'''Light''', or '''visible light''', is [[electromagnetic radiation]] of a [[wavelength]] that is visible to the human [[eye]] (about 400–700 [[nanometre|nm]]).  In a [[Science|scientific]] context, the word ''light'' is sometimes used to refer to the entire [[electromagnetic spectrum]].[http://www.lightsources.org/cms/?pid=1000166] (What Is a Light Source?) Light is composed of an [[elementary particle]] called a [[photon]].

Three primary properties of light are:

Three primary properties of light are:

===Electromagnetic theory===

===Electromagnetic theory===

[[Image:light-wave.svg|360px|thumb|A [[Polarization|linearly-polarized]] light wave frozen in time and showing the two oscillating components of light; an [[electric field]] and a [[magnetic field]] perpendicular to each other and to the direction of motion (a [[transverse wave]]).]]

[[Image:light-wave.png|360px|thumb|A [[Polarization|linearly-polarized]] light wave frozen in time and showing the two oscillating components of light; an [[electric field]] and a [[magnetic field]] perpendicular to each other and to the direction of motion (a [[transverse wave]]).]]

In [[1845]], [[Michael Faraday]] discovered that the angle of polarization of a beam of light as it passed through a polarizing material could be altered by a [[magnetic]] field, an effect now known as [[Faraday rotation]].  This was the first evidence that light was related to [[electromagnetism]].  Faraday proposed in 1847 that light was a high-frequency electromagnetic vibration, which could propagate even in the absence of a medium such as the ether.

In [[1845]], [[Michael Faraday]] discovered that the angle of polarization of a beam of light as it passed through a polarizing material could be altered by a [[magnetic]] field, an effect now known as [[Faraday rotation]].  This was the first evidence that light was related to [[electromagnetism]].  Faraday proposed in 1847 that light was a high-frequency electromagnetic vibration, which could propagate even in the absence of a medium such as the ether.

[[Category: General Reference]]

[[Category: General Reference]]