Reflection of light

Plane mirrors

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.

The way the light reflects is shown in the following diagrams. (It is usual to show the shiny surface by a line and the back of the mirror by a shaded section).

Laws of reflectionof light from a plane mirror

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 bertween the outgoing light ray is called the angle of reflection (r).