The laws of reflection
When a ray of light strikes a mirror, it is reflected. The incoming ray is called the incidence ray, the outgoing ray is called the reflected ray, and the line perpendicular to the mirror is called the normal. The mirror in this case it is a plane mirror. This just means it’s a flat mirror rather than a curved one.
There are two laws of reflection. They apply to all types of mirror:
The angle of incidence is always equal to the angle of reflection
The incident ray, the reflected ray and normal all lie on the same plane
To put in another way light is reflected at the same angle it enters
In the diagram above light rays are coming from a lamp. After reflects, some of the light enters the persons eye. To the person they seem to come from a position behind the mirror.
The image in the mirror looks exactly the same except one difference the image is laterally inverted (back to front)
Real and virtual images
A real image is an image that rays pass through and meet (focus) to form the image and the image can be formed on a screen
A virtual image is an image is an image the rays appear to come from the object and the image cannot be formed on a screen
Finding the position of an image in a mirror
The position of an image in a plane mirror can be found by experiment:
*diagrams p 151
Rules for image size and position
When a plane mirror forms an image:
The image is the same size as the object
The image is as far behind the mirror as the object is in front
A line joining equivalent point on the object and image passes through the mirror at right angles
