An Etymological Dictionary of Astronomy and Astrophysics

The process in which the direction of motion of → particles or → waves is changed randomly because of their → interactions (→ collisions) with other particles of the → medium transversed.

Two parameters govern scattering: 1) the wavelength (λ) of the incident radiation, and 2) the size of the scattering particle (r), usually expressed as the nondimensional size parameter, x = 2πr / λ. The size parameter defines three types of scattering:

1. x much less than 1 (or r much smaller than λ), → Rayleigh scattering;
   

2. x ~ 1 (or rλ), → Mie scattering; and
   

3. x much larger than 1 (or r much larger than λ), → geometric scattering.
   

See also: → atmospheric scattering, → backscattering, → Brillouin scattering, → coherent scattering, → Compton scattering, → elastic scattering, → forward scattering, → last scattering, → last scattering surface, → multiple scattering, → noncoherent scattering, → quasi-single-scattering approximation, → Raman scattering, → scattering angle, → scattering coefficient, → scattering of stars, → selective scattering, → single scattering, → spin-flip scattering, → surface of last scattering, → Thomson scattering.

Related terms: → diffraction; → diffusion; → dispersion; → distribution.

See also: Verbal noun of → scatter.