giving the light another chance to strike the light-sensitive rods. Whatever light is not absorbed on this return trip passes out of the eye the same way it came in—through the pupil.

The reason lies within the eye. In the eye are light receptors called cones and rods. Cones help us distinguish different colors, while rods help us see in dim light. The number of cones and rods ...

Because the front of the eye is curved, it bends the light as it goes in, turning the image on the retina upside down. Inside the retina, there are millions of special sense receptors called rods ...