- The occurrence of mirage can be explained as follows.
- The air on the road surface consists of many layers. On a hot day, the air near the ground has a low specific heat capacity, hence the temperature increase faster.
- The hot air becomes less dense than the cold air higher up.
- A ray of light originated from the sky is refracted away from the normal as the light is travel from denser to less dense air.
- As the air passes through the lower layers, the angle of incidence increases and the refracted ray is getting further away from the normal.
- Finally, at a layer of air close to the road surface, the angle incidence exceeds the critical angle. Total internal occurs and the light ray bends upward towards the eye of the observer.
- The observer sees the image of the sky and the clouds on the surface of the road as a pool of water.
- The spectrum of a rainbow is caused by total internal reflection in the water droplets.
- Different angles of total internal reflection produce different colours.