The Tyndall effect occurs when light is scattered by fine particles suspended in a gas or liquid, making the beam visible. The source describes particles larger than the wavelength of light scattering light at their surfaces. What is observed is scattered light rather than the directly transmitted beam.

Everyday examples include sunlight scattered through clouds, visible light paths in cloudy liquids, and beams in smoke. In research and laboratory work, the Tyndall effect is used to observe the presence and distribution of suspended matter and assess the turbidity of liquids or gases.

The effect depends on particle size, shape, and concentration. Scattered light is easier to observe with larger particles or higher concentrations. It also helps distinguish solutions from suspensions: dissolved molecules or ions are too small to produce obvious scattering, while appropriately sized suspended particles produce a more visible effect.

The Tyndall effect is visible-light scattering by suspended particles. It is used to observe suspended matter, assess turbidity, and distinguish solutions from suspensions.