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Physics Section C : Light and Images

Part 2: Information

There are 2 main types of lenses :

CONVEX or converging lens


These can produce upright, magnified images which are virtual (unreal)

As well as inverted, laterally inverted images which are real.

Uses: This lens can be used as a magnifying lens or a lens to correct  long-sight (presbyopia)

CONCAVE or diverging lens

These always produce upright images which are slightly smaller than their objects.

Uses: These lenses are used to correct short-sight (myopia).

How to draw ray diagrams

We represent the object by an arrow  () and 2 construction rays are drawn from the top of the object.

Link to Ray Diagram page

The position and size of an image produced by a convex lens, can be found by scale drawing using graph paper; or by using the lens formula.


u represents the object distance
v represents the image distance
f represents the focal length

When f  is measured in metres, represents the power of the lens in dioptres.

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Teresa Lewis 2016