A medium is moving when a standing wave is present on it. Of course, non-animated, or static, pictures can not capture this movement. This animation is meant to help you relate the actual movement of the standing waveform to the shape of a non-moving diagram. Non-moving diagrams are normally used to represent standing waves, so it is important to know how these static diagrams represent the motion of a wave.
This animation shows several harmonics for a standing wave on a medium fixed at both ends. Use the Previous and Next buttons (below display) to move through the scenes of the animation. Use the Run, Pause, Resume, and Stop buttons (left of display) to control the animation for each scene.
Each scene shows some aspect of a standing wave diagram. The normal static diagram is always drawn in white. These white lines are the shapes usually used to represent standing waves. The actual motion of the medium is the animated yellow line.
Note how the shape of a standing wave can be represented by drawing only the extremes of the motion. Such a diagram is said to illustrate the envelope of the wave.
The links below contain animations which realistically demonstrate several forms of standing waves.
As you page through the above animation be sure to notice the meaning of the terms 'antinode' and 'node'.
An antinode in a standing wave is the region where the medium is in motion. The locations of the antinodes do not change as the standing wave vibrates, and thus the name 'standing'.
A node is a spot on a standing wave where the medium does not move. This may seem unusual at first. However, there are places along the medium which are motionless as the standing wave oscillates. The locations of these nodal points do not move as the standing wave vibrates.