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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?
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.
For one purple forms by combining red & blue, two extremes on the rainbow. Although a rainbow contains all possible wavelengths, it doesn't contain all possible combinations of them, because wavelengths are arranged in order.
Hence, visible light has purple, also there can't be a purple in a rainbow.
We perceive more colors than those in a rainbow. The reason is that colors in a rainbow are generated by a single frequency of light, but the full gamut of colors we can perceive depend on a combination of three different frequencies (most humans have 3 different frequency sensors, the cones). in addition, there are other factors that complicate matters. Color perception is pretty complicated subject and there are entire books dedicated to it.
What few people seem to comprehend is that light is not visible. Some electromagnetic radiation is detectable and we refer to this range of detectable electromagnetic radiation as visible light. This is where most of the confusion arrises. Visible is a term used to describe conscious perception of visual representations. Trees, people and words on a page are visible.
When our eyes detect (not see) light, they send electrochemical impulses to our brains visual cortex. Here, our brain interprets these impulses and creates a visual representation of THE OBJECT, from which the light originates. We SEE the OBJECT (technically a visual representation of the object). So objects are visible, not light.
The color (visual sensation) of the object depends on the wavelength/wavelengths of light it emits/reflects, the cone/cones which detect it, the impluse/impulses sent to the visual cortex and finally, how our brain interprets the impulse/impulses. Different impulses/combinations of impulses, result in different visual sensations.
What I'm describing is how indirect realism affects our comprehension of colors. Purple is not in the visible light spectrum, but neither is red, orange, yellow or any other color. Colors are phenomenal sensations. They only exist in our brains.
