b) Mechanism of generation of light-induced impulse in the retina.
The photosensitive compounds (photo pigments) in the human eye are composed of opsin and retinal. Light induces dissociation of retinal and opsin which changes the structure of opsin. It generates an action potential in the bipolar neurons. These impulses/action potential are transmitted by the optic nerves to the visual cortex of the brain where the neural impulses are analysed and the erect image is recognised.