ELI5: If red and purple are at opposite ends of the visible spectrum, why does red seem to fade into purple just as well as it fades into orange? : explainlikeimfive: "Because purple isn't actually on the spectrum. It's not a real color at all (that is, there is no single wavelength of light that is purple). The visual spectrum runs from red to deep blue (indigo), but there's no purple on it anywhere. Purple exists all in our head, as a consequence of how our visual system works. How is that possible?
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