Question

How our eyes sees different combination of light colour though there are only limited shades of cones present

Answer 1

The retina of our eyes contains two types of photoreceptors – rods and cones. The cones detect colour. The rods only let us see things in black, white and grey. Our cones only work when the light is bright enough, but not when light is very dim. This is why things look grey and we cannot see colours at night when the light is dim.

There are three types of cones in the human eye that are sensitive to short (S), medium (M) and long (L) wavelengths of light in the visible spectrum. (These cones have traditionally been known as blue-sensitive, green-sensitive and red-sensitive, but as each cone is actually responsive to a range of wavelengths, the S, M and L labels are more accepted now.)

These three types of colour receptor allow the brain to perceive signals from the retina as different colours. Some estimate that humans are able to distinguish about 10 million colours.

he primary colours of light are red, green and blue. Mixing these colours in different proportions can make all the colours of the light we see. This is how TV and computer screens work. If you look at a screen with a magnifying glass you will be able to see that only these three colours are being used. For example, red and green lights are used to make our brain perceive the image as yellow.

When coloured lights are mixed together, it is called additive mixing. Red, green and blue are the primary colours for additive mixing. If all of these colours of light are shone onto a screen at the same time, you will see white.