Question

What is a mirage? How does it occur?

Answer 1

1. Mirage is an optical illusion caused by the refraction of light from the sky by heated air.
2. The air near the ground becomes hotter than the air at higher levels.
3. The refractive index of air increases with its density. Hotter air is less dense and has a smaller refractive index than cooler air.
4. If the air currents are small, that is, the air is still, and the optical density of different layers of air increases with height.
5. As a result, light from an object such as a car passes through a medium whose refractive index decreases towards the ground.
6. Thus, a ray of light from such an object successively bends away from the normal and undergoes total internal reflection, if the angle of incidence for the air near the ground exceeds the critical angle.