In the sun, there seems to be a pool of water about 20 meters ahead of the road.

From June to July, walking on the road under the scorching sun, you will find that the end of the road is watery, as if the sprinkler had just sprinkled water. The reflections of cars and pedestrians will be reflected on the "water surface". However, when you move forward quickly, the "water surface" will disappear or move further. This is the road "mirage" you see, which is very similar to the mirage you see in the desert.

After the pavement is exposed to sunlight, the air temperature on the pavement increases and the air density decreases.

However, the temperature and density of the air far away from the road surface remain unchanged.

In this way, there are two layers of air with different densities above the road, and the light will be refracted when it passes through the media with different densities, so a mirage occurs. The essence of mirage is the refraction of light.