|Size of light source
The Mie algorithm assumes that the incident light is in the form of a plane wave (e.g. from a point source of light at infinite distance).
Natural phenomena, such as rainbows or glories, are caused by light from the sun or, more rarely, from the moon. The sun and the moon are circular light sources with a diameter of about 0.5°, rather than point sources.
The main rainbow occurs around 138.6° with supernumeraries at 140.2°, 141.3°, 142.3° and so on. The averaging processes caused by the 0.5° source remove most of the "unnatural" ripples predicted for a point source.
Fig. 4 Effect of size of light source
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