The Tyndall effect is the scattering of light by particles in colloids, where shorter wavelengths like blue light scatter more strongly than longer wavelengths. Named after 19th-century physicist John Tyndall, the phenomenon is observed in everyday examples such as motorcycle smoke and tobacco smoke, and has practical applications in measuring particle size in aerosols and colloidal mixtures. The effect also explains why eyes appear blue, as light scatters within the iris's translucent layer containing microscopic particles.