Tyndall effect

Tyndall effect or Tyndall scattering is a light scattering phenomenon in colloidal dispersion, while showing no light in a true solution. This effect was first observed by the 19th-century physicist John Tyndall. It is similar to Rayleigh scattering, in that the intensity of the scattered light depends on the fourth power of the frequency, so blue light is scattered much more strongly than red light.

Overview

The Tyndall effect is seen when light-scattering particulate matter is dispersed in an otherwise light-transmitting medium, when the particle size is anywhere from features size to somewhat below the wavelength of the light. It is particularly applicable to colloidal mixtures and suspensions; for example, the Tyndall effect is used in commercial and lab settings to determine the size and density of particles in aerosols and other colloidal matter (see light scattering theory).

History

The effect was first observed by John Tyndall in 1859 and is credited to him. He observed that when light passes through a clear fluid holding small particles in suspension, the shorter blue wavelengths are scattered more than the other colors, and so it appears blue. This is known as the Tyndall effect.

See also

• Rayleigh scattering
• Mie scattering
• Critical opalescence