The Ray Theory of Light

Ever since you were a child you will have thought of light as being made up of rays.... beams or shafts of light that travel in straight lines. It must be one of the earliest ideas that mankind had of what light was.

In the Ray Model, a light ray is drawn as a straight line (always use a ruler!) and you indicate the direction of travel with an arrowhead. See the notes on the way to draw ray diagrams.

The Ray Model can be used to explain how images are formed in a mirror and why there is a difference between real and apparent depth. It is very useful in the field of optics. Ray diagrams can be used to show how shadows form, how lenses focus light, how the reflection of light works and how the direction of light is distorted by transparent materials of differing densities, such as glass or water.

You need to be able to construct ray diagrams and to know how to interpret them. Here are some useful links:

How to draw ray diagrams

How shadows are formed

Constructing a diagram to show reflection in a plane mirror

Constructing a diagram for reflection in a convex mirror

Constructing a diagram for reflection in a concave mirror

Constructing a diagram for refraction through a glass block

Constructing a diagram to illustrate real and apparent depth

Constructing a ray diagram to illustrate total internal reflection

Constructing ray diagrams for concave lenses

Constructing ray diagrams for convex lenses