Q. Which is the part of the human visual system where the receptors that sense light, i.e., the photoreceptor cells, are located? How do those cells work?

The photoreceptor cells form a lamina, the retina that covers the internal posterior region of the eyeball. The photosensitive cells of the retina are divided into two types: the rod cells and the cone cells. These cells have pigments that sense specific light wave ranges that are the frequencies and trigger action potentials conducted by the optical nerves to the visual area of the brain.