In MIT, I found this great lecture about rainbows and color by Walter Lewin. Some day, you should go and see his undergraduate lectures if you understand algebra and calculus. They are fantastic. This one, though, is one of the best I have seen. In here, he answers some of the properties of colors, why rainbows are the way they are, and why the sky is blue. The answers to the question of rainbow, though, is the most compelling, and perhaps astonishing. In it, he answers 6 questions on rainbows. They are: What are the order of the colors in the rainbows? How many rainbows are actually there? (1, 2, 3, etc?) If so, what are their color sequeces too?How large is the radius, in degrees? (yeah, the arc is part of a huge circle)Which part of the sky relative to the rainbow is brighter, inside or the outside? And finally, are rainbows polarized, and why? And as he says, once you know the answer, you won’t ever forget it. Vodpod videos no longer available.