A concave mirror is sometimes called a "convergent" mirror. This is because it causes parallel light rays to reflect and converge, or come together, at some focus point in front of the mirror. Depending on the observers distance from the mirror, a upright image may be formed, or an upside down image may be formed. Concave mirrors are used to gather light together. They are used in telescopes and microscopes. I saw some statistics on one of the concave mirrors used at Mount Palomar; the mirror was seventeen feet in diameter and weighed several tons! The use of mirrors in telescopes has increased astronomers capabilities in capturing and magnifying the incoming light from stars and other celestial bodies. The concave mirror is in direct contrast to the convex mirror, which bulges outward and does diverge parallel light rays away from a central focus point. Convex mirrors are used for security purposes, to enable a person to see around a corner, and for traffic safety, such as being mounted on school buses, so a driver can carefully monitor students coming around the front of the bus.