This isn’t a duplicate. I read those pages, but those didn’t answer my questions.
Please watch this.
Does visible light consist of red, orange, yellow, green, cyan and blue? No purple? My definition of purple has an RGB of 128, 0, 128:
If there’s purple in visible light, visible light and a rainbow are different since there’s no purple in a rainbow. If there’s purple in visible light, what’s the explanation behind the difference between a rainbow and visible light?
Best Answer
As your RGB value indicates, purple is "a mixture of red and blue".
Since a rainbow is created by an effect that separates the incident light into its wavelengths, and red and blue lie on opposite ends of the spectrum, the light coming out of a rainbow-generating droplet or any other prism does not "contain purple", since the wavelengths whose mixture purple is have been separated.
In essence, you will only see the near-spectral colors occuring in a rainbow - those which are approximately given by a single wavelength, or at most a narrow wavelength band:
The "purplish" colors here are more commonly called violet, but there is a history of debate about whether or not this constitutes purples.
Also, there is the fact that colors on the line of purples are very difficult to faithfully represent in any gamut, and even difficult to actually produce in nature.
At the end of the day, the spectrum is made up of wavelengths, and it is totally arbitrary to call them "red", "blue" or "yellow" or something else based on the way our trichromatic vision perceives them. Physics as such has no need for such color names.