How Mirages are formed?

Answer 1

This would be easier to answer with a diagram, but here goes. On a sunny day, air near the ground is warmer because of the heat radiated from pavement, sand, etc. Light from the sky will refract (bend or be redirected) because of the difference in temperature of the air closer and closer to the ground. When it reaches the eye of an observer, it will appear to have come from the direction of the ground. So, the observer sees light from the sky coming from the ground. We see light from the sky reflected from the surface of a puddle of water or a lake in much the same way - coming from the earth instead of the sky. So, we interpret it in the same way, as water. Palm trees and other images associated with mirages are the stuff of movies or the imagination.

Alternate (better) answer:

It may surprise you to learn that light usually does not travel a straight line

through the air, but rather its path is almost always curved slightly downward

as it travels. The curvature is usually small. We're never aware of it ... we

simply perceive an object to be located in whatever direction its light reaches

us from.

But when atmospheric conditions change drastically at different heights above

the surface, the downward curvature of light becomes extreme, and it may

become noticeable.

Since the light from an object curves strongly downward as it travels under

these conditions, the path by which an object is seen leaves the object at a

high vertical angle, can extend an unusually great distance, and arrives at the

observer from a high vertical angle ... it looks to the observer as if the object is

high off the ground.

These atmospheric conditions occur in places where there can be great swings in

temperature between day and night ... like deserts ... and where there can be

great differences of temperature at different heights above the ground ... like

deserts again.

It's no accident that the legends of flying horses and magic carpets originated

in the Arabian desert.

Answer 2

mirages are formed due to the total internal reflection of light

Answer 3

High gradient of atmospheric refractivity with altitude.