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Choose the correct options, and explain the reason for the correct and incorrect options.
Which among the following mixtures show the Tyndall Effect? A mixture of:
(a) air and dust particles
(b) copper sulfate and water
(c) starch and water
(d) acetone and water
(i) a and b (ii) b and d (iii) a and c (iv) c and d
Which among the following mixtures show the Tyndall Effect? A mixture of:
(a) air and dust particles
(b) copper sulfate and water
(c) starch and water
(d) acetone and water
(i) a and b (ii) b and d (iii) a and c (iv) c and d
View Answer
The correct option is (iii) a and c.
Air with dust (a) and starch in water (c) are colloids/suspensions, so their particles scatter light and show the Tyndall effect. Copper sulfate in water (b) and acetone in water (d) are true solutions with very tiny particles, so they do not scatter light.
| Mixture | Tyndall effect? | Reason |
|---|---|---|
| (a) air and dust particles | Yes | A colloid/suspension — the dust particles are big enough to scatter light. |
| (b) copper sulfate and water | No | A true solution — particles less than 1 nm, too small to scatter light. |
| (c) starch and water | Yes | A colloid — particles 1–1000 nm scatter the beam and make its path visible. |
| (d) acetone and water | No | Two miscible liquids form a true solution — no scattering. |
| Correct option | (iii) a and c | Only colloids and suspensions scatter light. |
