What are waves and what happens to them when they pass through a gap? Do different sorts of waves behave in the same way? Dr Andrew Norton of The Open University uses a ripple tank to demonstrate some of the key features of wave motion, and show how waves spread out when they pass through an aperture. Using a laser and a diffraction grating, he shows that light waves spread out in the same way. The album draws on material originally created to support The Open University course Exploring Science.