A student prepares soap solution in water and shines a beam of light through it. The path of the light beam b…

Question

A student prepares soap solution in water and shines a beam of light through it. The path of the light beam becomes visible inside the solution. (i) What phenomenon is responsible for this observation? (ii) What does this tell you about the nature of the soap solution?

Accepted Answer

## Model Answer (i) **Tyndall effect** — scattering of light by colloidal particles. (ii) Soap solution is a **colloid** (not a true solution); soap micelles are large enough to scatter light. *Source: Chapter 4, Section 4.5 Soaps and Detergents* ## Explanation The key phrase in the passage is: *"The soap micelles are large enough to scatter light. Hence a soap solution appears cloudy."* Examiners expect both parts answered: name the phenomenon (Tyndall effect) and state what it reveals (colloidal nature). Since this is 1 mark, keep it to one or two short lines — don't over-explain.

Science (086) — AI-generated practice question