Judged: two independent readers; copy check clear.
visual purple
visual purple Visual purple, also called rhodopsin, is a purplish-red pigment in the rod cells of the retina that is sensitive to light.
Visual purple, also called rhodopsin, is a purplish-red pigment in the rod cells of the retina that is sensitive to light. It is made of rod opsin joined with 11-cis retinal and absorbs light most strongly at about 500 nm.