A plane mirror is a flat mirror that is usually made of glass with
a very thin layer of silver on the back. The reflection occurs at
the silver and this is protected by a layer of paint.
Light hitting a plane mirror is reflected back and if you look into
such a mirror you will see an image of yourself. This image in the
mirror will be the same size as the object. Plane mirrors cannot be
used to focus an image of an object onto a screen.
Some mirrors have the silvering at the back (normal use) but others,
like those used in reflecting telescopes are silvered on the front.
Figure 3 shows you a ray of light hitting a plane mirror. A line drawn at right angles to the mirror where the light hits it is called the NORMAL to the surface at that point. The angle between the incoming light ray and the normal is called the angle of incidence (i) and the angle between the outgoing light ray and the normal is called the angle of reflection (r).
