Tyndall effect

The Tyndall effect is <a href="/facts/Light_scattering_by_particles/pyNaTyrj">light scattering by particles</a> in a <a href="/facts/Colloid/9EVucqND">colloid</a> such as a very fine <a href="/facts/Suspension_(chemistry)/S3xp96TL">suspension</a> (a <a href="/facts/Sol_(chemistry)/RsNj5FkF">sol</a>). Also known as Tyndall scattering, it is similar to <a href="/facts/Rayleigh_scattering/o0MQtPMM">Rayleigh scattering</a>, in that the intensity of the scattered light is <a href="/facts/Inversely_proportional/xDQmfh6t">inversely proportional</a> to the fourth power of the <a href="/facts/Wavelength/kcJU0ymz">wavelength</a>, so <a href="/facts/Blue/DHWb8MUa">blue light</a> is scattered much more strongly than red light. An example in everyday life is the blue colour sometimes seen in the smoke emitted by <a href="/facts/Motorcycles/owLPEqSr">motorcycles</a>, in particular <a href="/facts/Two-stroke/Al4uUeo9">two-stroke</a> machines where the burnt engine oil provides these particles. The same effect can also be observed with <a href="/facts/Tobacco_smoke/E3HVAVxL">tobacco smoke</a> whose fine particles also preferentially scatter blue light. 
Under the Tyndall effect, the longer wavelengths are <a href="/facts/Transmittance/xlyCG7ks">transmitted</a> more, while the shorter wavelengths are more <a href="/facts/Diffuse_reflection/wG9w4tAX">diffusely reflected</a> via <a href="/facts/Scattering/nMou7lEH">scattering</a>. The Tyndall effect is seen when light-scattering <a href="/facts/Particulates/RleGr5E6">particulate matter</a> is dispersed in an otherwise light-transmitting medium, where the <a href="/facts/Particle_size/KWwwGkn4">diameter</a> of an individual <a href="/facts/Particle/JHKr2w6h">particle</a> is in the range of roughly 40 to 900 <a href="/facts/Nanometre/a98sjHyu">nm</a>, i.e. somewhat below or near the wavelengths of <a href="/facts/Visible_spectrum/frPBh8o5">visible light</a> (400–750 nm).
It is particularly applicable to colloidal mixtures; for example, the Tyndall effect is used in <a href="/facts/Nephelometer/XT0HHfm5">nephelometers</a> to determine the size and density of particles in <a href="/facts/Aerosols/X1jXFLp2">aerosols</a> and other colloidal matter. Investigation of the phenomenon led directly to the invention of the <a href="/facts/Ultramicroscope/D6ntoSgX">ultramicroscope</a> and <a href="/facts/Turbidimetry/58Go49Ff">turbidimetry</a>.
It is named after the 19th-century physicist <a href="/facts/John_Tyndall/EH2dSEV3">John Tyndall</a>, who first studied the phenomenon extensively.

Tyndall effect open-in-new

Tyndall effect