Fata Morgana (mirage)

A mirage or mirage is based by deflection of light at different warm air layers on the Fermat's principle of optical effect. It is a physical phenomenon and not a visual perception deception or optical illusion.

Declaration and Occurrences

The optical density of hot air is lower than that of the cooler air. Light rays first pass through a cold layer of air, and then discharged into a shallow angle to warmer air layers are broken away from the optically thinner medium up to a total reflection. For a boundary between hot and cold air is necessary, that is, there must be no wind. If such air stratifications occur in deserts at a higher altitude, you can see reflections of the sky, the so-called mirage.

In temperate latitudes is observed reflections often near the ground over dark surfaces. On the left, an asphalt road can be seen. Because of their dark color, they heat up in the sun and with it the ambient air. Above are cooler air layers. On the road, grass, houses and a car mirror.

The graph illustrates the situation. An observer sees the car along the ray d Another beam i is due to the stratification of cold, so optically dense, on warm, so optically thin air broken to her. For them, it looks as if coming from the direction of the beam and v as was reflected the car on the road. If they are not familiar with the phenomenon of the mirage, they may suspect a wet road for the cause.

Also magnifications are possible, as multiple reflections, which leave the mirrored objects appear upright again. Sailors of previous centuries called such phenomena in ships, flying Dutchman.

The French physicist Gaspard Monge in 1798 investigated in Lower Egypt for the first time mirages scientific and interpreted.

Etymology

The term mirage comes from Italy and means fairy Morgana, a name from the popular medieval Arthurian legends throughout Europe. Morgana inhabited the mystical and unattainable for mortals island of Avalon. Accordingly, the appearance of a nonexistent island in the Strait of Messina between the Italian mainland and Sicily has been associated with her.

Mirage on the Mallee Highway in Australia