. When photo decomposition occurs, the rhodopsin is said to be bleached. Cones Cones are necessary for (i) daylight or bright light (photopic) vision,

The cone pigment, like the rhodopsin, consists of a combination of retinal and 'photopsin'. Photopsin is a protein which differs only slightly from scotopsin of the rhodopsin. Therefore, cone pigment = photopsin + retinal. However, there are three classes of cone pigment, (i) red sensitive (erythrolabe), (ii) green sensitive cehloro-labe) and (iii) blue sensitive (cyanolabe). They are maximally sensitive at the 430 nm (430 m u) for blue sensitive cones, 535 nm (535 m u) for green sensitive and 575 nm (575 m u) for red sensitive cones, wave lengths. Photochemistry of photopic vision Cones are required for photopic vision. When light of high intensity, strikes the cones, it may be presumed, that, the photochemical changes occur in the cone pigment in the cones and they are very similar to those of rhodopsin in rods. Note: 1. Photoreceptors, i.e, rods and cones, are present in outer part of the retina. Outer to this, the pigment layer i: situated. Some rays (which fall on the retina) are not ab sorbed by the photoreceptors and reach the pigment layer, where