The correct answer is Option (2) → (A), (B) and (D) only
Here is an analysis of each option:
- (A) Mixture of water and milk: Milk is a colloid (specifically an emulsion of fat and proteins in water). Because the particles are large enough to scatter light, this mixture shows the Tyndall Effect.
- (B) Sunlight passing through a canopy of dense forest: In a forest, mist or fog contains tiny droplets of water which act as colloidal particles dispersed in the air. These droplets scatter sunlight, making the beams visible. Thus, it shows the Tyndall Effect.
- (C) Solution of copper sulphate: Copper sulphate dissolved in water forms a true solution. The particles (ions) are smaller than $1\text{ nm}$, which is too small to scatter light. Therefore, it does not show the Tyndall Effect.
- (D) Light entering a smoke-filled room through a small hole: Smoke is a colloid (solid particles in gas). The dust and smoke particles scatter the incoming light, making the beam's path visible. This shows the Tyndall Effect.
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