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Meteorology and Weather
Rain and Flooding

What causes a double rainbow?


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May 05, 2015 4:17PM

The raindrop acts as a prism while the white light from the sun splits the white light into 7 colors (red, orange, yellow, green, blue, indigo, and violet), causing a rainbow. When all the sunlight doesn't escape the raindrop the light reflects causing a double rainbow.

The sunlight is reflected at two angles: the normal 40-42 degrees; and also at 50-53 degrees, which causes the second, inverted color, rainbow.

Also if you watch the double rainbow video on youtube, you can see what it looks like. A double rainbow is a phenomenom of optics that displays a spectrum of light do to the sun shining on droplets of moisture in the atmosphere
Double rainbows are formed by multiple reflections of light inside raindrops. The inner rainbow is brightest and formed by a single internal reflection inside the raindrop. The second rainbow is outside the first and reversed in color order; it is formed by an additional reflection (therefor the reversed color order). The larger and more uniform the raindrops the brighter the rainbows. I have seen three very bright rainbows and heard people say they have seen up to six (at least partial) rainbows.