Inferior mirage

When hearing of mirages, many people probably think of the desert. But this phenomenon can often be observed right in front of your doorstep. When driving a car1 who did not ever notice the "puddles" forming right in the middle of the road in the distance on hot summer days. This is nothing more than the famous "desert oasis mirage", having its roots in the principle of a mirage. A light ray is bended when passing layers of air of different density. In the case of the "wet road", the lowermost layer of air is heated up very much by the hot asphalt of the dark road so that it reflects the sky and so forms an inferior mirage.

Superior mirage

The other way around is the fata morgana, a superior mirage. In this case the warmer (i.e. the less dense) layer of air is over the cold one, for example over watery or icy surfaces or when there is inversion. The observing of a fata morgana requires a free horizon (in a plain or from the top of a mountain) and binoculars. This is because a fata morgana is not as gigantic and obvious as people often think. Often it becomes recognizable only by magnification. So, if you want to take photographs, you should use a good telephoto lens with a focal length of at least 500 mm.