Rayleigh scattering theory describes the classical (i.e., non-quantum) electromagnetic scattering of an electromagnetic plane wave from a sphere, with real index of refraction n, that is small compared to the wavelength of the light being scattered. In essence, the electric field of the incident wave causes charges within the particle to migrate so that positive charge accumulates on one side and negative charge on the other, leading to a dipole moment which oscillates with the same frequency as that of the incident wave. The index of refraction is in fact a measure of the polarizability of the medium – the proportionality between the strength of the electric field and the strength of the dipole moment induced.
The scattered wave in the Rayleigh limit is the electromagnetic radiation emitted by an oscillating dipole. Rayleigh theory works well as a description for scattering of light from molecules, even though molecules are not dielectric spheres. The typical size...