Bell Labs Wave Machine

The system is used to illustrate the propagation of transverse waves. The equipment consists of a long steel band through which are mounted a number of horizontal metal cross bars supporting spheres at their ends. The small spheres are painted with fluorescent paint so that they are more visible under black light in a darkened room. Reflection and absorption can be observed by using an alligator clip to attach an end bar to either a fixed support or a damper. By moving one end up and down with your hand at the right frequency you can generate standing waves.

A second, home-built apparatus works on the same principle but is much larger. It has longer rods with cylindrical masses at the end. The standing wave frequency is much lower. It is somewhat unwieldy--it takes two carts, and requires a bit more setup time.