Optical Board - Ray Diagram - Plane Mirror
To demonstrate how several light rays are used to locate the image in a plane mirror.
Optical board with half-silvered and front surface object mirrors and large plane mirror.
A single converging lens before the object keeps the light ray narrow.
A single central ray passes through a half-silvered mirror, with half deflected to act as the source at the tip of an object. By rotating the top mirror it can be shown that all rays starting at the object point (the rotating mirror) appear to come from the same point behind the plane mirror (the image point).
Sue Allen, The Gaussian formula and the elusive fourth principal ray, AJP 60, 160-163 (1992).