Virtual mirror on the road on hot days. Why is that?

[nktvnvn]

While in a car on a hot day, I notice that far ahead of me is a mirror-like surface on the road. I can see the reflections in that virtual mirror too. The mirror shifts with your moving forwards. Can anyone give a simple explanation? Thanks.

 

[Janus]

http://www.islandnet.com/~see/weather/elements/mirage1.htm

 

[Sarahchichi]

Yes, it is the formation of mirage. This happens due to the refraction of light from the space. Since there is temperature difference in various layers of the air ( that means the upper the sky, the lower the temperature, hence the density is higher.It is the same for the lower layer of air in the sky, the lower layers of air have higher temperature, hence smaller density).

SO, we can conclude that each layer of air has different refractive index. Therefore, a mirage like a pool of water is formed on the surface of the road