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Sometimes we might wish for a Spring shower plus a nearby supernova

The lower slice of rainbow is how it appears from small raindrops and light smeared out by the divergent rays from the sun’s 0.5° diameter disk. The colours are slightly washed out and inside the main bow there are 3-4 weak supernumerary bows produced by interference between light waves.

The upper slice is how we would see the bow from a rain shower lit by a distant point source of light, perhaps the diamond ring of a solar eclipse or a nearby supernova explosion. Without the blurring by divergent light beams the hues intensify and we see a deep and colourful array of sharp supernumerary interference fringes.

Simulations for a range of raindrop sizes - mean diameter 0.7mm with a std. deviation of 8%. Airy theory scattering calculations using a modified version of IRIS software.

©Les Cowley