The concept of colour and how it reflect of things

Question

I just had an idea, I want to know what something without colour cools like. I remember some animals/sea animals have abilities to see more colour and I wonder what it’s like in reverse

In: Physics

Answer 1

So first, light has a wavelength. An individual photon will have its color determined by that wavelength. For example, 630 nanometers (nm) gives you red, and 450nm gives you blue.

Now here’s the rub: humans don’t have an organ that can detect the exact wavelength of a photon (or a bunch of photons) of light. Instead they have photoreceptor cells. Each type absorbs a different range of wavelengths and sends a signal to your brain when that light is detected. The peak wavelengths for each type are 420nm (blue/violet), 534nm (green-yellow), and 564nm (red), for cone cells and 498nm (cyan) for rod cells. They don’t absorb just 420, 534, 564, and 498 nm photons, but rather a sort of band of light near those numbers. [Here’s a plot of how much they absorb of each color](https://en.wikipedia.org/wiki/Photoreceptor_cell#/media/File:1416_Color_Sensitivity.jpg).

So when you see a color you’re getting some mixture of signals. For example a light blue would be getting lots of the blue cone signal and a little of the rod or green cone signal. Your brain interprets that combination of signals as light blue.

To see more colors you would either have to have photoreceptors that absorb a broader range of light or more types of photoreceptors. If you had “wider” photoreceptors your brain would really be getting the same information, it would just have slightly different meaning. What you see as violet now might really be ultraviolet with wider range receptors, but since you’re still only using 4 signals you might not have as nuanced of a distinction between closely related colors. If you had more photoreceptors then your brain would just have to interpret how you “see” them. You’d literally see something that we can’t understand because it requires more wires in our brains than we have. Instead you have to imagine it from what we know: imagine you only see blue or black. Then you add a receptor and you get green and the mix between them. Then imagine adding red and the mix of red with the others. What’s next? Something that’s not blue, green, or red and is as different from them as they are from each other.