Which property is observed in an emulsion?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Tyndall effect and Brownian motion
An emulsion is a colloidal system of one liquid dispersed in another (for example milk, oil in water). Its droplets are of colloidal size, so like other colloids it
scatters light and shows the Tyndall effect, and
shows Brownian movement, because the droplets are bombarded unequally by molecules of the dispersion medium.
The droplets are also often negatively charged and can be precipitated by electrolytes.
Why the other options are incorrect
Option (1) Tyndall effect — Incorrect. True but incomplete; emulsions show Brownian movement as well.
Option (2) Brownian motion — Incorrect. True but incomplete; emulsions also show the Tyndall effect.
Option (4) Stable in nature — Incorrect. An emulsion of two pure liquids is unstable and separates into layers; it needs an emulsifying agent to be stabilised, and it can be broken by heating, freezing or centrifuging.
Note: This question is from the pre-rationalised NCERT book (2022-23). The topic is not there in the latest NCERT book (2026-27), and it is also out of the CUET 2026 syllabus.
NCERT (Pre-rationalised edition, 2022-23):
Emulsions – “… The droplets in emulsions are often negatively charged and can be precipitated by electrolytes. They also show Brownian movement and Tyndall effect. Emulsions can be broken into constituent liquids by heating, freezing, centrifuging, etc.”