Rainbows

Over the past two weeks, during the drive to or from work, I have seen three rainbows.  Yesterday I was able to get photographs of one when I arrived at work.

A double rainbow over the campus of Mid-Michigan Community College

Rainbows are caused by the refraction (bending) of light as it passes through water droplets in the air (rain, fog, etc.).  When the light hits the back of the droplets it is reflected back out of the droplet.  Because the light has been refracted or bent it separates into the different colors that make up the visible spectrum of light.  These colors can be remembered by thinking the following funny-sounding name - Roy G. Biv  (R=Red,O=Orange, Y=Yellow, G=Green, B=Blue, I=Indigo, V=Violet).  Sometimes, not all of the light comes back out of the lower half of the water droplet, but is instead reflected upward our the top of the droplets.  This causes a second rainbow to appear above the first one.  This second rainbow will be lighter than the one below it.

Rainbows are the caused the reflection and refraction of light

Because rainbows are the reflections of reflacted light, they appear opposite the source of the light.  If you see a rainbow in the morning it will be to the west, opposite the rising sun.  An evening rainbow will be to the east, opposite the setting sun.  Because we normally observe rainbows while standing on the ground, they appear to us an arc (a portion of a circle).  When people flying in airplanes see a rainbow, because it is not cut off by the ground, it often appears as a complete circle.

For more information on the science of rainbows check out this page from the National Oceanic and Atmospheric Administration (NOAA).

The opposite of the rainbow.

My camera does not have a wide enough field of view to take a photo of the complete rainbow, but I was able to piece together two photos to create a panorama showing the complete rainbow.