Rayleigh scattering is the elastic light effect that occurs when light waves come in contact with particles smaller than the wavelength of light. This is often the case when light waves interact with molecules or atoms. The effect is a diffusion of light, creating noticeable color changes. For instance, sunlight entering the Earth's atmosphere is scattered by particles in the atmosphere, creating the familiar blue sky color.
Mie scattering is the light effect of spherical particles without regard for the size of the particles. The effect is a spherical haze, or cloudlike effect, emanating from the point of the scatter. Scientists use this to gain information about the particles that scatter the light. For example, doctors look for Mie scattering in X-rays -- cloudy, circular images on the scan -- to determine whether an area in a patient's body has an unusual density, often attributed to cancer cells.
Tyndall scattering is a process similar to Mie scattering, but it is not reliant on the spherical shape of affecting particles. The effect is a color change, or diffusion of light, that allows only a few colors to pass. For instance, as light moves into an eye with little melanin, which absorbs light, the light is diffused and colors with shorter wavelengths escape. The resulting effect is blue eyes.
Brillouin scattering refers to the efffect density variations, such as temperature or magnetic changes, have on light. The density change alters the wavelength and angle of incoming light. You can see the effect of Brillouin scattering when you are underwater in a swimming pool and see the distortion of objects and people above the water. Water is more dense than air, causing additional resistance and distortion as light moves into the water.
Raman scattering is an inelastic light effect that occurs with Rayleigh scattering. While photons remain elastic, retaining the same energy, with Rayleigh scattering, some photons change frequency in reaction to a charge in the molecules causing the scatter. This is Raman scattering, which causes a specific change in the light wave that allows scientists to identify elements in a gas or liquid.