What is the Tyndall effect?

The Tyndall effect is the scattering of light by colloidal particles, making the beam path visible. Named after John Tyndall.

• True solutions: particles too small → no scattering, no visible beam.
• Colloids: particles large enough → beam visible as a cone of light.

Real-life examples:

• Sunlight in a dusty room
• Headlights in fog
• Blue colour of the sky
• Milk appearing white under light

The Tyndall effect is the visible scattering of a light beam by colloidal particles, used to identify a colloid from a true solution.