Explanation

The rods bear a long with thin cylinder, each of which contains a purple pigment rhodopsin made of a protein and vitamin-A. light splits rhodopsin into a pigment retinene and a protein scotopsin (opsin). This process is called bleaching. This depolarizes the rod cells to release a neurotransmitter, transmitting the nerve impulse to the bipolar cells, ganglion cells and then to the optic nerve fibres. In night, light is received from the moon and stars. It is resynthesized from retinene and scotopsin by vitamin-A.