Wave Machines

The nature of light has puzzled people for centuries. Some physicists thought that light travelled like a wave, while others thought that it travelled as a stream of particles shooting through space. Wave machines like this one became a popular way of visualising and explaining waves, and were also used as teaching models.

Demonstrating waves

This wave machine, from the collections of the Whipple Museum (Image 1), demonstrates how waves move. As you turn round the crank handle, the white balls at the top move up and down, giving the effect that the wave is moving along.

These are known as 'transverse' waves, and are the same type of waves made in rippling water. The other main type of wave is a 'longitudinal wave', such as sound waves.

Light: waves or particles?

The nature and behaviour of light has been a puzzling question for hundreds of years. Some experiments indicated that it behaved like a stream of particles, whilst others seemed to show that it acted like waves. The debate between supporters of the rival theories raged during the 19th century. Supporters of the wave theory of light built wave machines so that they could demonstrate the waves and their motion.

Today's physicists know that, strange as it may seem, light has properties of both particles and waves. This is explained by the theory of quantum mechanics.