Which of the following will show "Tyndall Effect"?
(A) Mixture of water and milk
(B) Sunlight passing through a canopy of dense forest
(C) Solution of copper sulphate
(D) Light entering a smoke-filled room through a small hole
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → (A), (B) and (D) only
The Tyndall effect is the scattering of a beam of light by particles large enough to scatter it, such as the particles of a colloid or fine particles floating in air, which makes the path of the beam visible. The particles of a true solution are too small to scatter light, so a beam passes through it unseen.
(A) Mixture of water and milk Correct. Milk is a colloid of fat and protein particles spread through water, so a beam of light through milk and water can be seen.
(B) Sunlight passing through a canopy of dense forest Correct. The air of the forest holds tiny drops of mist and dust, which scatter the sunlight and make its beams visible between the leaves.
(C) Solution of copper sulphate Incorrect. It is a true solution; its particles are smaller than about 1 nm and do not scatter light.
(D) Light entering a smoke-filled room through a small hole Correct. The smoke particles scatter the light, so the path of the beam shows up in the room.