Mirage

Many a time when we are in a place like a desert, we are tricked by nature to see a water body

An illusion of a water body is created by the hot conditions of the desert.

Even while driving a car in a very hot season we can experience the same illusion.

These illusions are called mirage.

Now let’s look at the science behind it

Say you are standing on a flat surface and looking at a tree in front of you

During the daytime, the temperature of the earth's surface is high.

So the layer of the atmosphere closer to the surface is hotter than the layers which are away from the surface.

Due to the relatively high temperature, the layer closer to the earth’s surface acts like a rarer medium.

Whereas the layers above it, due to relatively colder temperature, acts as an optically denser medium.

Now as light travels through the atmosphere and comes closer to the earth’s surface, it refracts due to the difference in temperatures.

The light actually travels from an optically denser to a rarer medium.

Now we know that if the refracted ray is parallel to the interface, the angle of incidence is called critical angle

When the angle of incidence is greater than the critical angle, then total internal reflection occurs.

If the rays of light are incident at an angle greater than the critical angle, the light will be reflected back into the same medium.

Due to total internal reflection, the light in desert-like conditions reaches our eyes after suffering multiple reflections.

And we see a shaky virtual image which seems to be a reflection of a water body.

The illusion of a water body is due to the change in the refractive index as the temperature of the atmosphere rises.

Let's check the important conditions for mirage formation

Mirages are visible only during daytime in very hot conditions; as the refractive indices of the layers of the atmosphere varies.

The angle of incidence must also be greater than the critical angle so that total internal reflection occurs.

Revision

Mirage is the illusion of seeing a water body on a very hot day or a very hot place like a desert.

Mirages are visible only during daytime in very hot conditions; as the refractive indices of the layers of the atmosphere varies.

The angle of incidence also must be greater than the critical angle so that total internal reflection occurs.

The image seems to be a reflection on the water as it shakes due to the multiple refractions and total internal reflection.

The End