Rainbows are the result of light from the Sun being refracted inside water drops in the atmosphere (for example, after it's rained or when one sprinkles water from a hose). In the picture below, sunlight is coming from the right (horizontal black lines).   Sunlight is a mixture of several different wavelengths (colors) of light and appears white to us (in the picture, the sunlight rays are drawn in black). Upon hitting a water drop, those rays refract (bend their direction of motion) into the drop. However, how much a ray will bend depends on its color, red bending less and violet bending more than the other colors.   Once inside, those rays travel in a straight line until they hit the inside surface of the drop. This time, the rays refract towards the outside but also reflect back. These reflected rays then continue to travel inside until they hit the surface once again, and a new refraction towards the outside happens.   This process of reflection and refraction happens several times, but in practice we only see two bundles of rays coming out because the intensity of the rays diminishes with each reflection/refraction ocurrence.   The explanation above is naturally a simplification of the whole process. In reality, there is a large number of water drops, each one contributing to the process. Also, what exactly one sees depends on where he or she is, as well as on the height ot the Sun in the sky.   This plot was generated using Mathematica 3.0 on a Power Computing Power Center Pro 180 Power Macintosh running MacOS 8.1 with 48 MB of RAM.                 back to the main page       Last modified on Sep 5, 1998.   © '97-98 Wagner Truppel       Please send comments to wtruppel@uci.edu