Question

One cannot see through fog because
A. Fog absorbs light.
B. Light is scattered away by the droplets in fog.
C. Light suffers total internal reflection at the droplets in fog.
D. The refractive index of fog is infinity.

Answer 1

Hint: Scattering of light is a process in which light interacts with matter and in course of this interaction, energy is absorbed from the incident beam of light and subsequently reemitted as scattered radiation.

Complete step by step solution:
The fog has a certain density and contains water droplets.
When light travels through fog, it interacts with the water droplets of the fog and is scattered by them. The scattering of light by fog droplets is not uniform in all directions. The light from various objects get scattered, so the eye cannot distinguish the objects, and thus one cannot see through fog.
Total internal reflection of light does not block the light, instead it causes optical illusions, and the object appears to be inverted or sparkle brilliantly.
In case of infinite refractive index, the total incident light is completely reflected, hence it is not the reason why one cannot see through fog. Similarly if light is absorbed by a medium, it is reflected back giving a rainbow effect.

Additional information:
The blue color of the sky is due to scattering of light, as scattering is stronger in the smaller wavelength. Thus, the blue-end of the visible spectrum is scattered more than the red-end.
The red color of sunlight and sunset is also due to scattering of light. During sunrise or sunset the sun rays travel a longer path through the atmosphere to reach the observer. As blue light is almost scattered away by the atmospheric particles, the red color in the remaining light becomes more prominent, making the sky appear red during sunset and sunrise.

Note: Scattering occurs only when light interacts with matter, which in case of fog is the water droplets.