this post was submitted on 11 Oct 2024
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Science Memes

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[–] chuckleslord@lemmy.world 26 points 1 month ago* (last edited 1 month ago) (16 children)

Purple, the color directly between red and blue, is a creation of your mind interpreting a band of light that triggers your red and blue sensing nerves, but no green is sensed. The actual band of light we can see goes from red to green to blue. Purple doesn't fall between those colors, meaning it wouldn't be included in a rainbow, and isn't any "pure" light you could see, since it doesn't fall on the spectrum.

Essentially, any time you see purple, you're seeing two different frequencies of light that your mind interprets as a single frequency.

[–] exasperation@lemm.ee 18 points 1 month ago (6 children)

What is violet at the end of the visible spectrum, then? We call the higher wavelength stuff ultraviolet, and violet looks purple to me, so I'm having trouble reconciling this stuff with what you're saying.

[–] general_kitten@sopuli.xyz 5 points 1 month ago* (last edited 1 month ago) (1 children)

We call it that but our eyes see the far end frequency as a colour that only very slightly activates blue sensitive cone receptors and no others. For red sensitive cones there is a slight bump in the high end frequencies also that makes it possible for them to look violet as it activates the blue sensitive and a bit of red sensitive receptors but a much purpler purple is made by combining high and low frequencies.

https://www.researchgate.net/figure/Normalized-spectral-sensitivity-of-retinal-rod-and-cone-cells_fig7_265155524

[–] AEsheron@lemmy.world 4 points 1 month ago

There is evidence to show that violet does actually weakly activates red cones too. This is because the violet light starts creeping up to double the frequency of the lower end of the red sensitivity, and so it can actually successfully activate it very weakly. There are other factors that can lessen or even fully negate that effect though, it's all kind of fuzzy.

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