Session 1, Page 8: Raindrops: Nature's Prisms

A prism is not the only thing that can produce a spectrum. A rainbow is an example of a spectrum which results from sunlight being refracted, dipsersed and reflected by raindrops. The Sun must be behind us for us to see a rainbow. When sunlight encounters rain or moisture in the air in front of us, some of the light is refracted and dispersed within the drops of moisture and reflected back to us, creating a rainbow.

As we can see from the refraction pattern in Figure 10, red is on the bottom and violet is on the top. Thus, one might expect that in a rainbow red would be on the bottom and violet would be on the top. The rainbow in Figure 9, however, shows that this is clearly not the case. Why is this?

Figure 12
Refraction and reflection pattern of sunlight within a raindrop. The light is refracted two times, once when entering the raindrop and again when exiting.

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	Figure 11 A rainbow seen over the Very Large Array (VLA) radio telescope outside of Socorro, New Mexico.