A double rainbow spanned the sky Monday in Redmond, Oregon, and provided an amazing sight on the first day of spring.

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There's plenty of science that goes into creating these stunning scenes, and double rainbows are the result of specific optical effects occurring simultaneously.

All rainbows require the presence of the sun and rain in order to form, but the sun must be at the viewer's back with rain falling in front of the viewer. Rain doesn't necessarily have to be falling on or near the viewer, though rain must be present ahead of the viewer toward the horizon.

As the sun breaks through the clouds and shines toward the raindrops, some of the sunlight encounters the raindrops and bends in a process called refraction. When the sunlight refracts, it separates into various wavelengths corresponding to different colors. Red and orange correspond to longer wavelengths, while blue and purple correspond to shorter wavelengths.

The refracted sunlight waves then bounce, or reflect, off the circular edges of raindrops and refract again as they exit the raindrops and travel through the air.

Raindrops are relatively round when the sunlight refracts through them, so a spherical arc stretching across the sky is the visual result. Viewers who are lucky enough to see a whole rainbow will observe a colorful arc spanning the entire sky.

Rainbows are, in general, a rare phenomenon because they can only occur when the refracted sunlight strikes a raindrop's edge at exactly 48 degrees. If the angle is less than 48 degrees, the sunlight will pass through the raindrop. Any angle greater than 48 degrees will cause the sunlight to reflect out of the raindrop, and no refraction will occur; a rainbow cannot form without refraction.

Double rainbows are even rarer but can occur during a particularly lucky scenario, as in the photo above shared on The Weather Channel Facebook page by Cameo Briana. In simplest terms, this is when two rainbows form at the same time.

The first, brighter rainbow is known as the primary rainbow and is created by the same process described above, only requiring the light to reflect off the raindrop once before refracting out of it.

The second, fainter rainbow is the secondary rainbow, which occurs when refracted light does not escape the raindrop after being reflected the first time. Instead, the refracted light reflects off the raindrop's surface a second time, which produces a secondary rainbow with its colors reversed. Fewer light rays are available to undergo the additional refraction process, so the secondary rainbow appears less vivid.

Theoretically, triple and even quadruple rainbows are possible depending on how many times refracted light is reflected within a rainbow. These additional rainbows are much rarer since the concentration of light rays available for reflection and refraction decreases with each optical process.