Quadruple rainbow photographed

BBC : For the first time, a phenomenon known as a quadruple rainbow has been captured on film. A rainbow is created when rays of sunlight are bent through raindrops; the constituent colors of the white light become slightly separated because they travel at slightly different speeds in water. A second rainbow can be created when some of the light takes another bounce within the raindrops and is bent at a different angle. Third and fourth rainbows can be created if the light continues to bounce. With each bounce the proportion of light gets smaller, which makes each succeeding rainbow fainter and thus harder to capture on film. Because the effect is so faint, a number of shots had to be taken and averaged after the fact, along with a digital enhancement known as unsharp masking, to show evidence of the tertiary and quaternary rainbows. To read more about spotting tertiary rainbows, read the article published in Applied Optics by Raymond Lee, a meteorologist at the US Naval Academy.