How Do Rainbows Form?
Rainbow over Canary Wharf, London, England. (Getty Images)
How do rainbows form?
They generally don't harbor gleaming pots of gold, but rainbows still symbolize hope for many around the world. In more technical terms, rainbows are meteorological and optical phenomena that result from light striking water.
Rainbows form when sunlight passes through water droplets of any kind, but most commonly through rain. As light enters a raindrop, it's refracted at the front of the drop, reflected at the back of the drop, and refracted yet again as it leaves the drop. This entire process is known as "dispersion" and the resulting wavelengths of dispersed light make up the various colors of the rainbow.
In fact, a rainbow is made up of more than 100 continuous colors, though distinct color bands may be apparent to an observer. The bands are the primary colors that make up the visible spectrum of the electromagnetic spectrum -- red, orange, yellow, green, blue, indigo and violet -- with violet on the lower band of the rainbow and red on the upper band.
The sun will always be at the observer's back and the rainbow will form at an angle of 42 degrees to the observer, with the entire arc of a rainbow spanning 84 degrees across the horizon.
On occasion, light is dispersed twice through rain drops and a second rainbow forms at an angle of roughly 52 degrees. In the double rainbow, the second rainbow's colors are inverted, with red colors on the lower band and violet colors on the upper band.
Of course, rain isn't the only cause of rainbows. They can be seen any time water and light are mixed. Rainbows appear from waterfalls, ocean spray, water sprinklers, dew and fog. At night, rainbows can even result from strong moonlight.
So, how close can you get to a rainbow?
In theory, a rainbow doesn't physically exist, so nobody can ever get a specific distance away from a rainbow. If you ever see a person that seems to be under or next to a rainbow, that person will not be able to see the same rainbow as you and will see a different rainbow if the right light and water conditions exist.
Rainbows are a beautiful phenomena that form through a unique mix of water and light. Perhaps one day, we'll be lucky enough to find the pot of gold at the end, as well.
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About the Author
Renny VandewegeFeatured Contributor Mississippi
Meteorologist Renny Vandewege has worked as a television meteorologist at WTOK in Meridian, MS, and KCTV in Kansas City, MO. He's an instructor of broadcast meteorology at Mississippi State University. He covered Hurricane Katrina and Hurricane Rita on television, and as a storm chaser, he has witnessed more than 40 tornadoes.