Referring back to Newton, sunlight is made up of different colors that we just can’t see. We see the sun as a beam of white light on a normal day until it hits a raindrop. Not meaning every raindrop is colorful in sunlight, but if the light beam hits the raindrops at a certain angle, the ROY G. BIV colors separate so we see them in the form of a rainbow.
Each angle of each raindrop is different because the colors enter each raindrop at different speeds. The light leaves the raindrop in only one color depending on the angle it entered. If the angle between the refracted light and the normal to the drop surface is greater than a critical angle, the light reflects off the back of the drop. The critical angle for water is 48 degrees so light will be reflected if the light beam hits at an angle greater than 48 degrees and passes right through if its less than 48 degrees. Violet bends the most, exiting at 40 degrees, white bends the least, exiting at 42 degrees, and the other colors exit the raindrops at various angles between 40 and 42 degrees.
None of this would be possible to figure out without Descartes’ calculations using laws of optics, the three stage refractionreflectionrefraction pattern. He even has a popular sketch that describes what’s required to see a rainbow. The sun is directly behind him and the light reflected from the raindrops in front of him are between the 40 and 42 degree angles it explained previously.
Knowing only on color of light is observed from each raindrop, the abundant amount of raindrops is required to make the color spectrum that is the characteristics of a rainbow. So even though