The light is mapped as an image along the surface of the retina by activating a series of light-sensitive cells known as rods and cones. These photoreceptor cells convert the light into electrical impulses which are transmitted to the brain via nerve fibers.n the Experiment, you learned that when an atom or molecule absorbs a photon, its electrons can move to higher-energy orbitals, and the atom or molecule makes a transition to a higher-energy state. In retinal, absorption of a photon promotes a p electron to a higher-energy orbital (a p-p excitation).