Reflection of light
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 and in a sextant.
Plane mirrors are also used in an overhead projector, an SLR camera, car wing mirrors, in microscopes, for lighting ancient Egyptian tombs and as reflecting number plates
The photograph shows multiple reflections in a plane mirror that once hung in the Fowey Hotel Cornwall.
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 diagram. (It
is usual to show the shiny surface by a line and the back of the mirror
by a shaded section).
Laws of reflection of 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 between the outgoing light
ray and the normal is called the angle of reflection (r).
Laws of reflection
1 The angle of incidence is equal to the angle of reflection.
2 The incident ray, the reflected ray and the normal all lie in the same plane.
schoolphysics Reflection animation
To see an animation of the reflection of light from a plane mirror click on the animation link.
schoolphysics Plane Reflection animation
To see an alternative animation of the reflection of light from a plane mirror click on the animation link.
schoolphysics Plane Reflection animation (tablets)
To see an animation of the reflection of light from a plane mirror that will also work on tablets click on the animation link.
schoolphysics Plane wave reflection animation (tablets)
To see an animation of the reflection of plane waves from a plane mirror click on the animation link.
A VERSION IN WORD IS AVAILABLE ON THE SCHOOLPHYSICS USB
