The Tyndall effect, also known as Tyndall scattering, is the scattering of light by colloidal particles or particles in suspension. It is named after the 19th century scientist 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 more strongly than red light. An example in everyday life is the blue color sometimes seen in the smoke emitted by motorcycles, particularly two stroke machines where the burnt engine oil provides the particles.