UCSB Science Line
 How do you see the colors of the rainbow? Question Date: 2005-06-10 Answer 1:This is a cool question and not easy to explain in an email, because I need to include a photo to explain my answer. In order to see a rainbow we need rain, sunshine and an observer who has his/her back to the sun. When white sunlight strikes a falling drop of water at a relatively low angle, the raindrop in the air acts like a prism and the light is broken into a spectrum of red, yellow, green, blue, violet. When the light enters the raindrop, it bends (it refracts) differently depending on their wavelength. The violet light bends at a rather sharp angle, the red light is bent the least. The light continues into the drop and is reflected from the back of the drop to the front. When the beam hits the front it is refracted again and emerges from the drop as the color spectrum that we see in a rainbow. Now, what we see as observers depends very much on where we are standing: Please look at the picture at the web site (which is also where I got my answer from): click here This picture explains how we see the colors red and violet, the other rainbow colors are not shown to keep the picture simple. When the light hits raindrop A only the red light is visible to the observer. We see the red light, because it is directed towards the observer's eyes. The violet light is directed above the level of the eyes and so are all the other colors, that is why we do not see them. However, in the lower drop (raindrop B) the red light is directed below the eye level and this time the violet light is visible to the observer. This means that we see only one color from each raindrop at a certain height. In the raindrop A we see only the red light, all other colors will exit at a lower angle and therefore be above the observers eyes. The sunlight will hit all the surrounding raindrops in the same way, so they will all bounce red light onto the observer and we will see a band of red. Raindrop B is much lower in the sky, so it doesn't bounce red light to the observer. At its height, the violet light exits at the correct angle to travel to the observer's eye. All the drops surrounding raindrop B bounce light in the same way. The raindrops in between A and B all bounce different colors of light to the observer, so the observer sees the full color spectrum. This explains how we see the colors of the rainbow and you now also understand that the way we see the rainbow (faint or strong) depends on where we are standing. If you have Internet you might go to here The website explains the colors of the rainbow very nicely and also tells you how a double rainbow if formed. Click Here to return to the search form.