Whenever we see a rainbow, why do we see red, orange, yellow, etc. on the top and not on the bottom??
In: Physics
A rainbow is caused by the sunlight passing from behind you. As it hits the raindrop, it refracts. It is reflected off the back of the raindrop, and refracts again as it passes back out towards your eye.
Refraction is a change in direction of light, caused by a change in the speed of light as it passes from one material (air) to another (water).
The thing is. Blue light refracts more than red light. So red light changes direction a little bit and blue changes direction a lot.
Hence the blue ends up lower than the red.
Rainbows are circular, centered on the line that connects you and the light source, and red is on the outside all the way around the circle, so technically it’s on the top, and also on the bottom.
The order is determined by how much the different colors of light bend when refracting at the boundary between air and droplets of water, and how it reflects off the back of the droplet: https://en.wikipedia.org/wiki/Rainbow#/media/File:Rainbow1.svg
Now that’s just the most visible rainbow. There are other paths light can take bouncing around a droplet and some of those have the colors coming out at a different angle and in a different order. (for example, image search for double rainbow)
Here’s something interesting to add to what the others mentioned. If you’re ever fortunate enough to see a double rainbow, pay close attention to the outer bow. You might notice that the red is on the inside instead of the outside. It’s caused by the same sunlight but it bounces twice inside the rain drops instead of once, so it comes out at a different angle and reversed.
So, the real answer is that you can see it the other way around. You just have to be looking at the right rainbow.
Latest Answers