Editing Rayleigh scattering (section)

{{Short description|Light scattering by small particles}}
{{About|the optical phenomenon|the magnetic phenomenon|Rayleigh law|the stochastic distribution|Rayleigh distribution|the wireless communication effect|Rayleigh fading}}
[[File:Leehasacamera - Sunset over the clouds (by).jpg|thumb|300x300px|Rayleigh scattering causes the blue color of the daytime sky and the reddening of the Sun at sunset.]]
'''Rayleigh scattering''' ({{IPAc-en|ˈ|r|eɪ|l|i}} {{respell|RAY|lee}}) is the scattering or deflection of [[light]], or other [[electromagnetic radiation]], by particles with a size much smaller than the [[wavelength]] of the radiation. For light frequencies well below the [[resonance]] frequency of the scattering medium (normal [[dispersion relation|dispersion]] regime), the amount of scattering is [[inversely proportional]] to the [[fourth power]] of the wavelength (e.g., a blue color is scattered much more than a red color as light propagates through air). The phenomenon is named after the 19th-century British physicist [[Lord Rayleigh]] (John William Strutt).<ref>Lord Rayleigh (John Strutt) refined his theory of scattering in a series of papers; see [[Rayleigh scattering#Works|Works]].</ref> 

[[File: Monochrome Rainbow.jpg|thumb|300x300px|Due to Rayleigh scattering, red and orange colors are more visible during sunset because the blue and violet light has been scattered out of the direct path. Due to removal of such colors, these colors are scattered by [[Atmospheric_optics#Sky coloration|dramatically colored skies]] and [[Monochrome rainbow|monochromatic rainbows]].]]
Rayleigh scattering results from the electric [[polarizability]] of the particles. The oscillating electric field of a light wave acts on the charges within a particle, causing them to move at the same frequency. The particle, therefore, becomes a small radiating [[dipole]] whose radiation we see as scattered light. The particles may be individual atoms or molecules; it can occur when light travels through transparent solids and liquids, but is most prominently seen in [[gas]]es.

Rayleigh scattering of [[sunlight]] in [[Earth's atmosphere]] causes [[diffuse sky radiation]], which is the reason for the blue color of the [[daytime]] and [[twilight]] [[sky]], as well as the [[golden hour (photography)|yellowish]] to reddish hue of the low [[Sun]]. Sunlight is also subject to [[Raman scattering]], which changes the rotational state of the molecules and gives rise to [[polarization (waves)|polarization]] effects.<ref>{{cite journal|doi=10.1364/AO.20.000533|pmid=20309152|title=Rayleigh scattering|journal=Applied Optics|volume=20|issue=4|pages=533–5|year=1981|last1=Young|first1=Andrew T|bibcode=1981ApOpt..20..533Y}}</ref>

Scattering by particles with a size comparable to, or larger than, the wavelength of the light is typically treated by the [[Mie theory]], the [[discrete dipole approximation]] and other computational techniques. Rayleigh scattering applies to particles that are small with respect to wavelengths of light, and that are optically "soft" (i.e., with a [[refractive index]] close to 1). [[Anomalous diffraction theory]] applies to optically soft but larger particles.