What is a rainbow? Where is the sun when you see a rainbow? Author Donald Ahrens in his text eteorology Today describes a rainbow as "one of the most spectacular light shows observed on earth". Indeed the traditional rainbow is sunlight spread out into its spectrum of colors and diverted to the eye of the observer by water droplets. The "bow" part of the word describes the fact that the rainbow is a group of nearly circular arcs of color all having a common center...



http://www.eo.ucar.edu/rainbows/