# Colors sensitivity by human eye and light wavelength [duplicate]

I do not understand why human eye sees different colours from the LED TV/screen. Especially violet.

For example, how we get yellow color on TV. There are 3 small diodes Red, Green Blue in LED screen and when we see yellow, that means Red and green diodes are on and blue is off. This I understand, because wavelength for red approximately 600 nm, for green 500 nm and yellow in the middle, let say 550 nm. In this case 600 for red + 500 for green gives 550 in average, that is yellow. it is ok, good explanation.

But what about violet? Violet wavelength is 300 nm, We get it on TV if we combine red and blue. red is 600 nm, blue is 400 nm and in average I expect that we will see it as 500 nm green. But why we see it as violet which should be 300 nm? Anyway, we cannot get at all 300 nm if we combine red (600), green (500) and blue (400).

All wavelengths here are very approximate from the top of my head maybe +/- 50 nm or even more. Exact numbers do not matter, the main point is the idea how human eye see different colors.

## marked as duplicate by Bill N, Kyle Kanos, Jon Custer, sammy gerbil, JamalSApr 12 '18 at 12:22

• It's more a question of physiology than physics. Do you mean why do we perceive 128,0,255 RGB as the same as violet? – Martin Beckett Apr 10 '18 at 16:14
• A good explanation of the topic jamie-wong.com/post/color – Martin Beckett Apr 10 '18 at 16:20