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Red, green, and blue are the primary colors of light—they can be combined in different proportions to make all other colors. For example, red light and green light added together are seen as yellow light. This additive color system is used by light sources, such as televisions and computer monitors, to create a wide range of colors. When different proportions of red, green, and blue light enter your eye, your brain is able to interpret the different combinations as different colors.

My question is can the eye distinguish between light of the pure wavelength corresponding to yellow(monochromatically yellow) and a mixture of red and green light that also produces the sensation of yellow in our eyes?

The question is related to the question asked here: Why does adding red light with blue light give purple light?

But my specific question is whether the eye can distinguish between the mixture and a pure wavelength of purple.

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Abhijeet Melkani
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  • Monochromatic yellow stimulates receptors for red and green. Some people (maybe only women?) seem to have receptors for yellow. –  Jan 07 '17 at 12:05
  • But the question is can the eye differentiate whether the receptors are being stimluated by a mixture of red and green or by a pure monochromatic yellow? – Abhijeet Melkani Jan 07 '17 at 15:50
  • As for some people having receptors for yellow colour I didn't know that. Can you refer me to some sources? – Abhijeet Melkani Jan 07 '17 at 15:50
  • The word to google for is tetrachromic colour vision: https://en.wikipedia.org/wiki/Tetrachromacy –  Jan 07 '17 at 20:59
  • My understanding is that most people can not see pure yellow light at all, since they are missing the cones for that wavelength. Is that right? – mafu May 09 '17 at 16:45
  • Oh no. Yellow wavelength stimulates both the red and the green cones in the retina. So does a mixture of red and green light. If your thinking was correct how would people see say cyan or brown? People don't have cones for them either. – Abhijeet Melkani May 09 '17 at 16:50
  • I'm voting to close this question as off-topic because it's about [biology.se] and not physics. – Kyle Kanos Dec 18 '18 at 10:56

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No, you can't, because the RGB cones in your eyes are stimulated in some way from yellow and if you stimulate them so they will send the brain the same signal - in the end of the day your brain only gets a signal and interprets it, if you cheat it with the source of the signal - you have no way of finding out.

But, people with glasses sometimes differentiate between a mixture and monochromatic light, that is because their glasses suffer a bit from dispersion, so each color in a mixture of light does a slightly different way and find itself on a different place on your retina.

Ofek Gillon
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