The correct option is (c) 2 and 3 only.
Explanation
The Tyndall effect is the phenomenon of scattering of a beam of light by a medium containing small suspended particles-such as smoke or dust in a room or mist in a forest. This effect makes the path of the light beam visible. It is a characteristic property of colloids.
Statement-wise Analysis
- Statement 1 is Incorrect. The Tyndall effect is caused by the scattering of light by particles, not by the absorption of light. When sunlight passes through the canopy of a dense forest, the tiny water droplets scatter the light in all directions, making the rays visible.
- Statement 2 is Correct. Mist consists of tiny droplets of water suspended in the air. In colloidal chemistry, this is classified as an aerosol (liquid dispersed in a gas). These droplets are large enough to scatter light, acting as colloidal particles.
- Statement 3 is Correct. While pure air is a homogeneous mixture of gases, the air in a forest containing suspended particles like dust, smoke, or mist droplets acts as a heterogeneous mixture (specifically a colloidal dispersion). The Tyndall effect is only observed in heterogeneous mixtures where particles are large enough to scatter light, unlike in true solutions where particles are too small to do so.
Key Takeaway: The Tyndall effect arises from the scattering of light by colloidal particles (such as mist or dust) in a heterogeneous mixture, rendering the path of light visible.