Do you know ghouls from goblins and ghosts?
photoreceptor pho·to·re·cep·tor (fō'tō-rĭ-sěp'tər)n. A nerve ending, cell, or group of cells specialized to sense or receive light.
A specialized structure or cell that is sensitive to light. In vertebrate animals, the photoreceptors are the rods and cones of the eye's retina. See Note at circadian rhythm.
An electronic device that converts light energy into electrical signals. Photoreceptors are used in photocopy and facsimile machines, cameras, and solar cells.