Lenses are optical devices than make use of refraction to bend light.
There are two main categories of lens:
1. Converging Lens
Also called a convex lens. Characterised by being thicker in the middle than at the edges. Light passing through such a lens tends to converge.
| Some examples of converging lenses:
|
2. Diverging Lens
Also called a concave lens. Characterised by being thinner in the middle than at the edges. Light passing through such a lens tends to diverge.
| Some examples of diverging lenses:
|
NOTE: In this chapter we will not be looking at ray diagrams for diverging lenses. We will only be concerned with converging lenses.
Symbols Used to Represent Lenses
We usually only need to know if a lens is concave or convex and so we can distinguish them using the following symbols:
 Symbol for converging lens |
 Symbol for diverging lens |
These are easy to remember as they are similar to the shapes of the lens they are representing:
|
|
|
| Examples |
|---|
| (a) How does the converging lens affect the direction of light rays passing through it?
It bends the light rays towards the principal axis. (b) How does the diverging lens affect the direction of light rays passing through it? It bends the light rays away from the principal axis. (c) What conditions will allow light rays incident on a converging lens to meet on the other side of the lens? The rays will need to bend such that light rays from the same point O on an object can converge and meet at a common point I (image). |
| Lenses | Next >> |
| Links |
|---|
| https://en.wikipedia.org/wiki/Lens |