Answer
Retinal is the basic light sensitive molecule and it combines with certain proteins called opsins to form three visual pigments --red, green and blue. In other words, these pigments enable cones to perceive red, green and blue objects. However, we can see objects of other hues and colors for which there or no visual pigments in cones.The explanation is that the red , green and blue color spectra overlap to facilitate perception of yellow, orange, purple and white objects.
Work Step by Step
Retinal is the basic light sensitive molecule and it combines with certain proteins called opsins to for four l types of color sensitive visual pigments. The visual pigment of rods is rodopsin which has little or no color sensitivity. In cone retinal combines wit three types of opsins to give three basic types of cones sensitive primarily to red light(560 nm wave length) ; green light(530 nm) and blue light (420 nm).
As a consequence, cones enable us to see objects that are red , green or blue. However , we can see objects of different colors, yellow, orange etc. How is this possible? The explanation is that the red , green and blue color spectra overlap. In other words a cone my be able to see both red and green light, but perceives red light more easily or more strongly. So, if cones see both red and green light( equally strongly) coming from an object, the object will appear to be yellow in color. If the receptors absorb the red light more strongly than the green light, the object will appear orange in color. This mixing or spilling over of the color spectra enables us to see other colors other than red, green and blue. If all light wave lengths are perceived with equal strenght the "color" is perceived as white.
