Two Nodes and One Antinode

A standing wave with two nodes and one antinode is produced on a wave demonstrator.

Discussion

In this and the following seven movies standing waves are generated in a 0.90 m short-rod demonstrator by a mechanical wave driver coupled to the left-most rod of the demonstrator; the right-hand end of the wave demonstrator is held stationary by a clamp. This arrangement approximates the situation in which both ends of the wave demonstrator are stationary.

As with a string that is fixed at each end, standing waves on a wave demonstrator with both ends stationary must have a N + 1 nodes and N antinodes, where N = 1, 2, 3,.... The corresponding wavelengths are given by the expression λ = 2L/N, where L is the length of the wave demonstrator, 0.90 m.

When the wave driver is oscillating at a resonant frequency of the wave demonstrator, waves moving away from the wave driver on the left-hand end of the wave demonstrator interact with waves reflected from the right-hand end to form standing waves. At non-resonant frequencies, this interaction does not result in stationary standing waves. In these movies the wave driver frequencies were those for which the standing waves had maximum amplitude.

With the wave driver frequency set at 0.883 Hz, a standing wave with two nodes and one antinode is generated.