Obtain two convex lenses, a strong and a weak one. Take the weak convex lens with the long focal length and fix it to a metre ruler with plasticine.

Point the ruler at a distant lamp and using a piece of paper, find the image that the lens forms.Do this by moving the piece of paper away from the lens until a clear image is formed. Click to see a 120Kb video.

Use the strong lens as a magnifying glass to view the image, as pictured on the left. Now remove the paper screen and look through both lenses at the lamp.

The lamp should appear inverted, larger and closer