Tolouse, France : A team led by atmospheric scientist Jean Ricard of the National Centre for Meteorological Research in Tolouse, France, has identified twelve rainbow ‘flavors,’ each with its own distinct characteristics.
For a rainbow to form there has to be sunlight and rain. As the white rays of the sun encounter the raindrops, they bend because of a phenomenon called refraction. Since the seven colors that make up white light have different wavelengths, they bend at different rates and disperse, resulting in a rainbow.
The team began by identifying the four characteristics that can encompass all rainbows. There is, of course, the classic rainbow with the red band on top and the blue-violet on the bottom. Then there are the ones with the Supernumerary bows – Bright bands either at the top or bottom. In between some rainbows, you might notice Alexander’s bands, dark areas caused by less light being reflected. And finally on occasion, one may be lucky enough to witness a ‘double rainbow’ – One that features a normal bow and a second, fainter bow above, except with the colors reversed. Armed with this knowledge the team began analyzing hundreds of rainbow photos and grouping them in one of the four categories.
In addition to identifying 12 distinct rainbows, Ricard and his team also stumbled upon another discovery. They found that while the angle and size of raindrops do matter, the biggest determinant of rainbow colors is the sun’s distance from the horizon. If the sun is further up in the sky, the colors will be largely blue and green. If it is closer to the horizon, only the red and orange will be visible.
