The physiology of vision is very complicated with many structures and abilities. Light entering the eye passes through the lens and is focused on the retina . The retina is the sensory tunic of the eye and consists of two layers, the pigmented layer and the nervous layer. It is within the nervous layer that photoreceptors process light stimuli to form our vision. These photoreceptors, rods and cones , sense and encode the patterns made by light in our surroundings.
Rods are responsible for dim-light and peripheral vision and are more sensitive to light than cones.
However they do not provide either sharp images or color vision. Conversely, cones serve to operate in bright light and provide high-acuity color vision. As light excites these photoreceptor cells, electrical signals are sent through sensory neurons of the bipolar cells and ganglion cell axons to the bundle of nerve fibers called the optic nerve. Thus, light could be viewed as photons traveling in wave-like fashion at very high speeds. As visible light passes through a prism, the waves are bent to produce a band of colors called the visible spectrum .