Home : Waves : Lenses & Mirrors
A lens is a piece of transparent material that is shaped
so that it will refract light (or other waves) in a certain way.
Convex lenses (like the one shown here) bend light inwards - if you hold a convex lens close to an object
then it appears much bigger than it really is. In this way, the lens is working like a magnifying glass.
A concave lens, on the other hand, is thinnest in the middle and thick at the outside: the opposite to a convex
lens. They bend light in the opposite way is well - light is bent outwards.
If you look at something close up through a concave lens then it appears smaller than it really is.
In lesson 4 we saw that light bounces off a mirror
at the same angle that it hits: the angle of incidence is equal to the angle of reflection.
For a curved mirror this is still true, but the situation is a little more complicated.
Like lenses, there are two different types of curved mirror. Mirrors that curve inwards are called concave (like the one
shown here); and ones that curve outwards are convex.
A concave mirror will reflect light inwards to a point. These types of mirror can be used to make a solar furnace which
focusses light from the Sun onto a single point: creating very high temperatures.
Convex mirrors reflect light outwards. These mirrors are often used in shops so that the shopkeeper has a good view of the
whole of their shop.