Explain how the eye responds to different light levels.

Light is a sensory stimulus detected by the eye. Rods and cones located in the retina of the eye respond to light. The pupillary reflex is responsible for controlling the amount of light hitting the retina. In bright light, circular muscles contract and radial muscles relax to make the pupil smaller. In dim light the opposite occurs, circular muscles relax and radial muscles contract in order to make the pupil wider and allow more light into the eye.