1. Any scattering process produced by spherical particles whose radii are smaller than about one-tenth the wavelength of the scattered radiation. Compare Mie scattering. See also size parameter. In Rayleigh scattering, the scattering coefficient varies inversely with the fourth power of the wavelength, a relation known as the Rayleigh law. The angular intensity polarisation relationships for Rayleigh scattering are conveniently simple. For particles not larger than the Rayleigh limit, there is complete symmetry of scattering about a plane normal to the direction of the incident radiation, so that the forward scatter equals the backward scatter.

2. The scattering of light by a body with a particle diameter (Dp) less than 0. 03 micrometres is termed Rayleigh Scattering. The wavelength of light scattered is dependent on the Dp, and the amount of light scattered is dependent on the number of particles present per unit volume. Shorter visible wavelengths, such as blue, are scattered by smaller particles than are the longer wavelengths like red.