Question

The colour of milk is white because

• A. Both the dispersed phase and the dispersion medium are colourless but the dispersed fat globules scatter all wavelengths equally
• B. Both the dispersed phase and the dispersion medium are white and the dispersed fat globules scatter all wavelengths equally
• C. The dispersed phase and the dispersion medium are made up of complement colours
• D. None of the above

Answer 1

The correct option is A Both the dispersed phase and the dispersion medium are colourless but the dispersed fat globules scatter all wavelengths equally

Colloidal dispersions can be easily distinguished from true solutions by their light-scattering properties. The nature of this scattering largely depends on the ratio of the size of the dispersed phase to the wavelength of the light. The particles in the colloid tend to scatter all wavelengths equally and this phenomenon is called Tyndall Scattering.
In fact, the white colour of fog and milk are chiefly attributed to Tyndall scattering. The butterfat droplets in milk are actually transparent, but the scattering disperses the light in all directions so extensively that we cannot see through milk.