Discovery

Shadow Shapes

Stand a comb upright on a sheet of paper and shine a torch through it. What happens to the shadows when the torch is moved away? (Use a pencil to draw the shadows on the paper.)

Light rays travel in straight lines from the light source (the torch bulb). When the comb is close to the bulb, the light rays angle outwards in the shape of a fan as they pass through the comb, and so the shadows fan out too. When the torch is further away, the angles between the shadow lines become almost parallel. What pattern of shadow lines can you make using sunlight as a light source?

This is one of the simple online activities from Questacon, adapted from their Light Exsciter Pack.

Vicki Hyde is the editor of New Zealand Science Monthly.