how we perceive colour
There may appear to be a missing link at this stage. We’ve discussed electromagnetic radiation wavelengths and how colours are assigned to specific wavelengths, but you may be wondering how our eyes and brains perceive red, yellow, green or any colour just by seeing a wavelength.
The answer lies in the eye itself. Photosensitive cells exist in the retina at the back of the eye that absorb light. These cells are categorised as either Rods or Cones. The Rods are responsible for sensing light intensity and the Cones for distinguishing colour. Three sets of Cones exist which are receptive to the different wavelengths of red, blue and green. Although wavelengths of many frequencies are entering the eye only the maximum wavelengths of red, green and blue are responded to and therefore perceived as the colour. In the case of yellow, you will notice from the electromagnetic spectrum that the yellow wavelength sits between the red and green wavelengths, so the red and green receptors in the retina receive equal stimulation with little impact being made on the blue receptor resulting in the eye perceiving yellow.
