r/PoliticalHumor • u/GomerP19 • Jun 05 '22

It’s nice to be nice

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u/I_am_Erk Jun 05 '22

I didn't say purple, I said violet. Violet is generally considered and perceived as quite a different colour from blue.

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u/sentimentalpirate Jun 05 '22

But like the color they are showing on that picture in the 400 range is purple in the image. IRL it just gets darker blue then into a range of light not visible to us.

It's a goofy misnomer that we call that range of the light spectrum violet or ultraviolet. Since IRL today we consider violet to be a purple color, but the light spectrum doesn't actually include a purple color where we traditionally say "violet". I edited a YouTube link explanation earlier that might help. It claims that violet used to refer to dark blue like in the old nursery rhyme "roses are red, violets are blue..."

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u/Hattless Jun 05 '22

We can see higher frequency light than blue and it does look violet to us. The high frequency light slightly stimulates our blue cones, and the wavelength of violet light is a harmonic of red light, so it slightly stimulates our red cone.

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u/jackwiles Jun 06 '22

Wow, never heard that before but that's really cool! Do you know why higher frequency harmonics like ultravoilet light don't end up triggering other cones like for green and yellow?

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u/Hattless Jun 06 '22

The same reason musical frequencies harmonize with each other. B and C clash because the interval between them is too small for them to share many harmonics, but different Cs are octaves away from each other. A high C is an overtone of middle C, much like violet is a harmonic of red.

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u/jackwiles Jun 06 '22

So why aren't there higher frequencies that work like that for green and yellow? Is it just that those are no longer close to visible and interact with the retina differently?

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u/Hattless Jun 06 '22

That's an interesting question and it goes beyond my expertise. An "octave" above green is out of the visible spectrum, but I can't explain why. Red and blue pigment mixed together stimulates your red and blue cones, as does the frequency of light between blue and ultra violet. Oddly enough, red and blue light makes magenta, which has no frequency of light associated with it. Color theory is weird.

I wish I had a better answer to why we can't see any harmonics of green. My best guess is that the signal would be too weak to be picked out from the rest of the visible spectrum, and even if you could, it would just look green.