Show Details

Rainbow Roots

October 25, 2007

A listener asks: How are rainbows made?


Behind the colors of the rainbow. I’m Bob Hirshon and this is Science Update.

Listener Jacob Campbell of Brookfield, Wisconsin wrote to ask how rainbows are made. We turned to optical engineer Suzanne St. Cyr, who works on satellite telescopes that NASA launches into space. She says that the sun’s rays are made up of white light, which actually contains every color in the visible spectrum. Rainbows form when sunlight hits water droplets, separating these colors.

When white light hits the water droplet at an angle that slows the light down and causes the light to bend. The blue bends the most, and red the least and so that spreads the colors out in the sky according to their speed.

If you have a science question, call us at 1-800-why-isit. If we use your question on the air, you’ll win a Science Update mug. I’m Bob Hirshon, for AAAS, the science society.