Light scattering

Light scattering is the redirection of light by particles, irregularities, or variations in a material. Its behavior depends on the scatterers’ size, shape, and optical properties, as well as the light’s wavelength.

Rayleigh scattering: Elastic scattering by particles much smaller than the wavelength of light, with intensity strongly weighted toward shorter wavelengths. This small-particle regime explains why air preferentially scatters blue daylight.
Tyndall effect: Visible scattering of a light beam by particles dispersed in a medium. It makes beams visible in colloids and helps distinguish them from true solutions.
Electromagnetic radiation: Energy carried through space by oscillating electric and magnetic fields. Light scattering is the redirection of this radiation through interactions with matter.
Absorption (optics): The transfer of optical energy into a material, often converting it to heat or other forms of energy. Absorption removes energy from a beam rather than redirecting it into other directions.
Mie scattering: Scattering by spherical particles whose sizes are comparable to or larger than the wavelength of light. Droplets and aerosols often fall in this size range, producing less wavelength-selective scattering.
Blue sky: The blue appearance of the daytime sky, produced mainly by wavelength-dependent scattering in the atmosphere. Atmospheric scattering redirects more short-wavelength visible light toward observers.
Wavelength: The distance between successive corresponding points on a wave. Comparing wavelength with particle size helps determine the scattering regime.
Reflection: The return of a wave from a boundary into the medium from which it came. Reflection redirects light at an interface, while scattering can occur throughout a material.
Geometric scattering theory: An approximation that treats light as rays when scatterers are much larger than its wavelength. Large particles can redirect light in patterns better described by ray optics than wave-scale approximations.
Red sky at sunset: The reddish appearance of the sky near sunset, when sunlight travels a long path through the atmosphere. The extended atmospheric path scatters much of the shorter-wavelength light out of direct sunlight.

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