The demonstration: Have one student anchor the outstretched Slinky at one end (preferably on the floor, so the wave can be seen better). Another student (also at floor level) creates a pulse — a traveling disturbance — by moving the free end left and right (then stopping). The pulse will travel down the Slinky, and reflect off the anchored end to travel back the other way. If the first student moves the end of the Slinky back and forth continuously, he or she generates a wave.

The Slinky is the medium for the wave: it’s the substance that is the means of transmission.

This kind of Slinky wave is transverse: that is, the Slinky moves transverse to (or at right angles to) the direction of the wave. Any given segment of the Slinky oscillates back and forth, while the wave itself travels along the Slinky and back.

Because the wave is moving along the Slinky, it is called a progressive wave. (Later, in Topic 4, we will see that there are standing waves that do not progress.)