The phenomenon of "Mirage", that is usually observed in deserts, is the result of which of the following?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Refraction of light
Refraction is the bending of light when it passes from one medium into another of different optical density. In a desert the sand heats the air next to it, so the air near the ground is hotter and less dense than the air above, and its refractive index is lower.
Light from the sky or a distant tree travelling down through these layers bends a little more at each layer, away from the vertical.
Near the ground it turns upward (the last turn is total internal reflection) and reaches the eye from below.
The eye traces the ray back in a straight line, so it sees an inverted image of the sky on the ground, which looks like a pool of water.
Why the other options are incorrect
Option (1) Reflection of light — Incorrect. Ordinary reflection is light bouncing off a surface such as a mirror; in a mirage there is no reflecting surface, only layers of air.
Option (3) Scattering of light — Incorrect. Scattering by air particles gives the blue colour of the sky and the red of sunset, not displaced images.
Option (4) Interference of light — Incorrect. Interference of light waves produces the colours of soap bubbles and oil films.