And why are the colors are always in ROYGBV order?
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They’re not congregating – rainbows don’t physically exist.
We see that structure only because of the way our eyes work, and the spectrum of light that is visible to us.
If we could see infrared as another color it would be in the rainbow as well, and the same for ultraviolet. [Here’s an example.](https://twitter.com/statto/status/1297233651458093056)
There is a prism – droplets of water.
These act to diffract the light into the visible spectrum.
The colours represent different wavelengths of visible light, with the higher frequency wavelengths at the outer rim of the circle (rainbows are circles, we only see part of them)
The only reason the colours are defined that way is because it was defined that way.
It’s a rainbow because light radiation is a spectrum of high to low energy packets. We just interpret it as colors in the visible spectrum that we see. Uv and IR are colors too if our eyes adapted. It’s in that order because again hi to low energy which also correlates with wavelength or size.
When you hear gamma rays traveling thru space that’s a form of radiation, super high energy and if we had engineered eyes there’s a color to that too at the super dark violet end let’s say (making this up). The sun itself is not white or yellow for similar reasons. It has energy across the spectrum and it’s mixed up the colors.
So, in high school physics classroom they will teach you about “refractive index” and how that number is useful for calculating the angle of refraction. For example light would go from air to water and enter the water at X angle, then ask at what angle would the light keep travelling underwater. You can only answer this question if you know the refractive index *n*
Now what I’m not aware of being taught in high school physics classrooms is this small detail about this *n* value and that is that *n* is a different value for different wavelengths. You have the same optical medium (air, water, etc.), but how dense these media are (i.e what exact number they have) depends on the wavelength. This dependence is why most (but not all) of white light separates in nature into a rainbow. I mean, dispersion (this rainbow effect) is taught, but not that it’s because *n* is wavelength dependent.
They’re in that order because of their wavelengths. If you lookup the electromagnetic spectrum it goes in order from lowest to highest. It starts out with AM, FM, television, microwaves, infrared, ROYGBIV, ultraviolet, X-ray, gamma rays
Each rain drop is a little prism that refracts (bends) light. Each wavelength of light bends by a different amount, which creates a visible color spectrum ordered by wavelength.
As the rain falls, the apparent angle between it, the sun, and *you* changes, meaning that the portion of its refracted light spectrum that reaches your eye changes. At first you see the red portion. Then as the raindrop descends you see orange, yellow, green, etc.
The colors it emits don’t change. Only which portion of this spectrum that reaches your eye changes.
From afar, we wouldn’t notice such a small detail. But we certainly do notice when a whole field of billions of raindrops all refract sunlight from roughly that direction.
This is 16 hours old but no one really answered the last question; the colors of the rainbow go in that order because the different wavelengths of light are bent at different angles by a prism.
All waves refract when they hit a boundary between 2 different densities (like water/air and glass/air, but also different layers within a solid material or even layers of the atmosphere). I don’t know if it’s as simple as “different wavelengths always refract at different angles” but in a prism, that’s what’s happening.
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