The amount of light entering the eye is controlled by a reflex action. The size of the pupil changes in response to bright or dim light. This is controlled by the muscles of the iris.

Short-sightedness can be corrected by placing a concave lens in front of the eye, as shown in the diagrams below. Someone who is long-sighted can see distant objects clearly, but they cannot focus ...

We are at a critical time and supporting climate journalism is more important than ever. Science News and our parent organization, the Society for Science, need your help to strengthen ...