Uses of plane mirrors

Plane mirrors have many uses apart from the obvious one of simply to look in.

They are used in periscopes, for signalling, in kaleidoscopes, to see round dangerous bends, in meters, as mirror tiles, in a sextant, in an overhead projector, an SLR camera, car wing mirrors, in microscopes and as reflecting number plates to mention only some!

Kaleidoscopes are interesting, they are made with two mirrors at an angle to each other. The smaller the angle the more images there are.

Light beams as pointers — if you shine a beam of light onto a plane mirror and then twist the mirror the light beam also moves. If you measure it you will find that the light moves through twice the angle that the mirror turns.

Light beams have therefore been used as sensitive and weightless pointers.