How is the rainbow formed?
When sunlight travels through the atmosphere and encounters water droplets, mist or even dew, the light as it passes through a different medium will be refracted. This results in visible or white light being split into the colors of a rainbow--red, orange, yellow, green, blue, indigo and violet. Since red has the longest wavelength, it is seen on the larger, outside curve of the rainbow and the rest of the colors become progressively shorter in wavelength, ending up with violet, found on the inside curve of the rainbow. Rainbows caused by sunlight appear in the section of the sky opposite the sun. The colors of a rainbow make up what is called the visible spectrum, which can be detected by the human eye.