2.5: An Iridescent Cloud Over Colorado

This photo is of an iridescent cloud. When parts of a cloud are thin and are made of small water droplets, diffraction causes them to show the whole spectrum of colors. The water droplets in the cloud are small and about the same size. The sun needs to be behind thick clouds, and the droplets of the thin cloudsc coherently diffract the incoming light. Many clouds originate with a region made of uniform, small water droplets; however, these clouds become to thick or too far away from the sun to show brilliant colors.