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refraction-reflection-in-droplets

Left. From Newton’s personal annotated copy, “… the Sun shining upon these Drops certainly causes the Bow to appear to a Spectator standing in a due position to the Rain and Sun… this Bow is made by refraction of the Sun’s Light in Drops of falling Rain.” Right. Parallel rays strike a pair of droplets of water. The refections and internal reflections manifest themselves with red in the upper band, blue and violet in the lower.