Explain the formation of Mirage.

Explain the formation of Mirage.

(or)

Sometimes during the hot summer days, it appears that there is water on the road, but there would really be no water. What do you call this phenomenon? Explain why it happens.

Answer:

• During hot summer days, it appears that there is water on the road. But when we go there, we don't find any water.
• This phenomenon is called as 'Mirage'. It occurs due to refraction of light.
• During hot days, air above the road surface is very hot and air at higher altitudes is cool.
• As the density of air increases with height, Refractive Index of air increases with density.

• The cooler air at the top has greater refractive index and the hotter air at the surface has low refractive index.
• If we take any two layers of air, upper layers are denser and lower layers are rarer. So light rays travel far away from Normal.
• When the light rays pass through particular layer where incident angle is greater than critical angle, Light rays reflect back due to Total Internal Reflection.
• These rays reach the observer's eyes and appears as there is water on the ground.
• Hence, we see the inverted virtual images (Mirages) on the ground surfaces during hot summer days.