Atmospheric Scattering Phenomena

In the range of angles between the two rainbows there will be no rays corresponding to one or two reflections. Therefore the sky brightness is reduced. This darker region is called Alexander s dark band (Greek philosopher, 200 B.C.). 

The scattered light in rainbows is almost fully polarized since the angle of incidence for the internal reflection is close to Brewster s angle (tan = n). 

The angle of observation for a rainbow is shown in Fig.4.23. A rainbow is circular due to the spherical symmetry of the drops. From an aeroplane, in principle, a complete rainbow can be seen centred around the shadow of the aeroplane. Common atmospheric scattering phenomena such as the rainbow have been discussed in [4.30]. Other phenomena such as atmospheric haloes, mirages, the green flash etc. have been treated in [4.31]. 

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In 1985, a British team at Halley Bay Station, Antarctica, discovered the existence of a hole in the ozone layer above that continent. This totally unexpected phenomenon needed an explanation, and Susan Solomon—a young National Oceanic and Atmospheric Administration (NOAA) scientist—first proposed a good theory for it. While attending a lecture on polar stratospheric clouds, she realized that ice crystals in the clouds might do more than just scatter light over the Antarctic. Her chemist s intuition told her that the ice crystals could provide a surface on which chemical reactions of CFG compounds could take place. 

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