Mirage is an optical phenomenon. The rise of hot air on the sandy or rocky surface refracts light, resulting in a mirage. Mirages occur in desert areas about 6 miles (9.6 kilometers) from the coastline, making objects a mile (1.6 kilometers) away or farther seem to be moving. It makes land navigation very difficult, because in the mirage environment, natural features become blurred. A mirage will make it difficult for a person to distinguish distant objects. At the same time, it will also blur the outline of the distant field of vision. You feel as if you are surrounded by a piece of water, and the higher part of that area looks like an "island" in the water. Mirages also make it very difficult for you to identify targets, estimate range, find personnel, etc. However, if you go to a higher place 10 feet (about 3 meters) (3 and 1 / 3 meters) above the desert ground, you can avoid the hot air close to the surface and overcome the mirage. In short, as long as the viewing height is slightly adjusted, the mirage phenomenon will disappear, or its appearance and height will change.
Mirages often occur in the sea and desert. Mirages are the result of refraction of light in gas layers with different densities along the straight line. There are many kinds of mirages: according to its position relative to the original, it can be divided into upper mirage, lower mirage and side mirage; According to its symmetrical relationship with the original, it can be divided into normal mirage, side mirage, forward mirage and anti mirage; According to the color, it can be divided into color mirage and non color mirage, etc.