Here are interesting articles about “How do we see colours?”
The mechanism which helps us see the colours is pretty interesting. The article discusses what happens when light falls on an object (for example, on a ripe red apple). White light comprises waves of different wavelengths. The receptors in our eyes are sensitive to a certain range of wavelength ~ 380-750 nm. Gringer, Public domain, via Wikimedia Commons
These light sensitive receptors (photoreceptors) are of two types - rods and cones. Rod cells get activated when light is dim (in darkness). Cones are the ones which get activated in bright light. Cones can be again classified into three types based on the range of wavelengths of light they are sensitive to - small wavelength(S-cone), medium(M-cone) and larger ones (L-cone).
How do you perceive the apple as red? When white light falls on the apple, there are certain pigments in the skin of the ripe apple, which absorbs light in shorter wavelength range. The longer ones then get reflected and reach our eyes. This activates a larger proportion of cones cells of L-type as compared to S & M type cones. This signal is then taken by the optic nerve to the visual cortex of the brain where it gets interpreted as “red” by us.
In one eye, the number of rods cells(110 million) are ~18 times that of cone cells (6 million). Also, cones are located in the central region and rods are at the periphery on retinas.
