CBSE Class 9 Answered

The Tyndall effect is an effect of light scattering by colloidal particles or particles in suspension. It is named after the 19th century Irish scientist John Tyndall

Colloidal particles are much larger than atoms or molecules. It follows from scattering theory that Tyndall scattering (by colloidal particles) is much more intense than Rayleigh scattering (by atoms or molecules). Tyndall scattering can be used to determine the size of colloidal particles. Tyndall scattering is also often used to describe light scattering by macroscopic particles such as dust in the air. However, this phenomenon is more like reflection, as the macroscopic particles become visible in the process.