In a human eye, there are three types of cones that allow us to see colors. the three different types are most sensitive to red,
green, and blue light, respectively. all three contain retinal bonded to a large protein. the way that retinal bonds to the protein can change the length of the potential well within which the electrons are confined. how would the length have to change from that given in the introduction to make the molecule more sensitive to blue or red light?
Once retinal has absorbed a photon which initiates effects that create nerve impulses, the impulses get carried to the brain, which then processes the impulses along with other signals, ultimately allowing the eyes to see.