When the light rays are all focussed correctly on the retina. The cells which can absorb the light begin their work. In the retina, some cells detects the low levels of light, and some cells detect bright light. The cells that absorb light are shaped in two shapes: rod cells are shaped: longer cylindrical /colour appears white, while cone cells are rounder in shape/ colour appears yellow.
Rod cells: It can absorb any colour of light , especially '' green'' light. Our brain does not use any signals from rod cells to identify colour, only shades of light and dark. It is called the black & white vision system, also in low light it helps us see the movements and shapes of our surroundings.
Cone cells: It can let us detect colours. Human have three kinds of cone cells, each of them has a different pigment. Using lony red, green & blue, it can see all the colours of a rainbow. If our brain detect the equal amount of those colours, then we can see the object as white. eg: the white page of paper appears white.
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