'Adaptation' of eyes in dark is due to

Two types of photoreceptor cells are present in retina, ie, rods and cones. (i) Rods: These cells are active in dark Rhodopsin, a vision pigment is present in rods. In strong light, rhodopsin is bleached due to splitting of its two components, ie, scotopsin and retinal. But is reformed in dim light, ie, dark. (ii)Cones: These cells are active in strong light. Iodopsin a pigment is present in cones. These cells produce hare coloured image in bright light.