Tyndall effect (intro)
Pure Substances and Mixtures · Chemistry
Study notes
In a dark room, a torch beam is passed through (A) salt water and (B) diluted milk. What is seen? Step 1: Salt water is a true solution — particles < 1 nm, far smaller than light's wavelength. Step 2: Light passes through without scattering → beam invisible in A. Step 3: Milk is a colloid — fat/protein particles ~100 nm, comparable to light's wavelength. Step 4: Particles scatter light in all directions → glowing beam visible in B. This visible beam is the Tyndall effect, proving B is a colloid.