Rayleigh scattering

Summary

Rayleigh scattering is the scattering of electromagnetic waves by particles much smaller than the wavelength. Each particle becomes a small oscillating electric dipole driven by the incident field and radiates in all directions. The scattered power grows like the fourth power of the frequency, so short wavelengths are scattered much more than long ones. It explains why the clear sky is blue and why sunsets are red, and it limits the transparency of optical fibers.