Fog bow

The Fogbow is a phenomenon of atmospheric optics in the form of a circular, white luminous arc. It is a special form of the rainbow, which is caused by very fine droplets.

Observation

A fog bow is formed when the sun shines on a wall of fog and the light is reflected by at least 5 micron droplets. In comparison with the rainbow band of fog bow is about twice as wide and the incident white light is not refracted in different colors. The Fogbow is opposite the sun forever. Its radius is up to 42 ° and decreases with decreasing droplet size. If the droplets are smaller than 5 microns large drops, the fog bow to the naked eye can no longer be perceived. To observe it is further necessary that, before the fog wall stands as an observer with the sun at your back, otherwise the light is already too much weakened by the fog.

Often, the fog bow can be observed together with the Spectre of the Brocken and the glory.

Formation

The principle of origin based on the one as in the rainbow on the refraction and reflection of light rays in the water droplets of the mist. Since the droplets are smaller than 50 micrometers, and diffraction effects play a role. The small droplet size with the result that the reflected light beams are superimposed so that the sheet is white.

The smaller the droplets, the fainter the Fogbow appears. From about 5 microns droplet size, the light is so weak that it can no longer be perceived.