The Tyndall effect is the phenomenon in which the particles in a colloid scatter the beams of light that are directed at them. This effect is exhibited by all colloidal solutions and some very fine suspensions. Therefore, it can be used to verify if a given solution is a colloid. The intensity of scattered light depends on the density of the colloidal particles as well as the frequency of the incident light.

When a torch is switched on in a foggy environment, the path of the light becomes visible. What is the factor responsible for light scattering?

The water droplets in the air

The answer is 3. The water droplets in the air.

When a torch is switched on in a foggy environment, the path of the light becomes visible due to Tyndall scattering. Tyndall scattering is the scattering of light by particles that are much smaller than the wavelength of light. In fog, the water droplets are much smaller than the wavelength of light. This causes the light to be scattered in all directions, making the path of the light visible.

The dust particles in air are also much smaller than the wavelength of light. However, they are not as numerous as the water droplets in fog. This is why the path of the light is not visible when a torch is switched on in a dusty environment.

The lens of the torch does not scatter light. It only refracts light, which is why the light appears to be bent when it passes through the lens.

So the answer is 3. The water droplets in the air.