Rayleigh scattering

Rayleigh scattering is the scattering or deflection of <a href="/facts/Light/jeofpMn4">light</a>, or other <a href="/facts/Electromagnetic_radiation/Ynx7ujCW">electromagnetic radiation</a>, by particles with a size much smaller than the <a href="/facts/Wavelength/kcJU0ymz">wavelength</a> of the radiation. For light frequencies well below the <a href="/facts/Resonance/q7VLALUz">resonance</a> frequency of the scattering medium (normal <a href="/facts/Dispersion_relation/oo7RM5eg">dispersion</a> regime), the amount of scattering is <a href="/facts/Inversely_proportional/xDQmfh6t">inversely proportional</a> to the <a href="/facts/Fourth_power/1UBbw22E">fourth power</a> 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 <a href="/facts/Lord_Rayleigh/HcJyYdk5">Lord Rayleigh</a> (John William Strutt).

Rayleigh scattering results from the electric <a href="/facts/Polarizability/0XRkXwUu">polarizability</a> 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 <a href="/facts/Dipole/G1vRqruD">dipole</a> 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 <a href="/facts/Gas/hVVAoodV">gases</a>.
Rayleigh scattering of <a href="/facts/Sunlight/WPkJRC7s">sunlight</a> in <a href="/facts/Earth%2527s_atmosphere/FV97Am25">Earth's atmosphere</a> causes <a href="/facts/Diffuse_sky_radiation/HqPS9Ugv">diffuse sky radiation</a>, which is the reason for the blue color of the <a href="/facts/Daytime/nR7raDjV">daytime</a> and <a href="/facts/Twilight/hNUKeCT8">twilight</a> <a href="/facts/Sky/wwvQ84J1">sky</a>, as well as the <a href="/facts/Golden_hour_(photography)/dySzFmdl">yellowish</a> to reddish hue of the low <a href="/facts/Sun/CadPCVHh">Sun</a>. Sunlight is also subject to <a href="/facts/Raman_scattering/obhSpgrR">Raman scattering</a>, which changes the rotational state of the molecules and gives rise to <a href="/facts/Polarization_(waves)/fP33m0eD">polarization</a> effects.
Scattering by particles with a size comparable to, or larger than, the wavelength of the light is typically treated by the <a href="/facts/Mie_theory/5mJc3SrT">Mie theory</a>, the <a href="/facts/Discrete_dipole_approximation/6aNfztC5">discrete dipole approximation</a> 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 <a href="/facts/Refractive_index/yjkzvgeE">refractive index</a> close to 1). <a href="/facts/Anomalous_diffraction_theory/efCe57oV">Anomalous diffraction theory</a> applies to optically soft but larger particles.

Rayleigh scattering open-in-new

Rayleigh scattering