How come red & purple are on opposite, far ends of the electromagnetic spectrum, but when mixing colors together in kindergarten, purple is halfway between red & blue?

Question

Shouldn’t common sense dictate that either both be one, or both be the other?

In: 1934

Answer 1

Ok. It’s important to separate two different colours here:

1. There is violet. Violet is at the very edge of the visible specturm, which is why wavelengths beyond violet are called ultraviolet light (UV).
2. Then there is purple and magenta. This isn’t a real colour. it’s a colour that’s created in your brain. That’s because the eye has three different cells that see light, so called “cone” cells. We have one type that responds to Short wavelengths (Short/blue, with a peak response near violet-blue), one for Medium wavelengths (Medium/”green”, with a peak response at Greenish-yellow) and one that sees Long wavelengths (Long/”red”, peak response at Yellowish-red). Depending on how strong the response is from each type of cells you see different colours. You see purple when Blue and Red cones are triggered, but not Green (ie, a mix of light from the blue and red spectrum).