A lens is used to focus light. Lenses do this by refraction.

Laboratory experiments with light

In the laboratory you will use a ray box to produce three parallel rays to do your light experiments with. Diagrams you have to draw in examinations often refer to the results of these experiments.

Why does a ray box produce three parallel beams of light?

Rays from an object at infinity travel parallel to each other - therefore using a close-up light source that produces parallel beams of light is useful in the laboratory. Those beams act in the same way as rays coming from an object a long way away - like the Sun.


The convex lens

The concave lens

The lens equation

Click here to go to the page on how to construct diagrams of the passage of rays through lenses

See also the refracting telescope and the camera

For correction of sight defects - see the eye