CEE 5244 Lecture Notes - Lecture 33: Ice Crystals, Sun Dogs, Antisolar Point
5 Apr 2016
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Lecture - 33: rainbows come from the interaction of sunlight with round water droplets. Preferred single-reflection path with ~42 deflection angle. See http://mysite. verizon. net/vzeoacw1/rainbow. html: drag incoming ray, and you get a stationary behavior at 42 . Rainbow arc always centered on anti-solar point. The whole sun is bent 0. 6 at the horizon. It has actually set before its refracted image sets: red image sets first, followed by green. The blue has long been scattered away: the halo, and sun-dogs, 22 halo around sun due to hexagonal ice crystals. Often more noticeable around moon at night (less glare: sun-dogs (parhelia) join halo, level with sun. From horizontally situated ice crystals: akin to leaves falling in stable horizontal orientation. Colored due to refractive dispersion through ice crystal: sun-dog geometry, glorys and heiligenschein (shadow-hiding, a circular rainbow about the anti-solar direction is called a glory. Water droplet phenomenon: the anti-solar point may also get bright due to shadow-hiding.
