What defines Rayleigh scattering?

Rayleigh scattering is characterized as an elastic scattering process where the energy of the photons remains constant. This means that when light interacts with small particles (such as gas molecules) in the atmosphere, the direction of the light is changed, but the energy (or wavelength) of the light does not change in the process. This phenomenon is significant in understanding why the sky appears blue. Shorter wavelengths of light are scattered more effectively than longer wavelengths, but the energy of the photons does not alter during the scattering event.

The scattering process depends on the size of the particles relative to the wavelength of light, but in Rayleigh scattering, these conditions result in elastic scattering, keeping the energy and wavelength of the photon unchanged while redirecting it.