Medium

The water is the medium, the material through which the ripples travel. To describe a wave, distinguish the direction the wave travels from the direction in which a point of the medium moves as the wave passes.

The individual coils are part of its medium: they move locally but do not travel along the spring with the wave.

A wave's speed depends on the medium it travels through. In the same medium, if the wave speed stays the same, producing more waves each second leaves less distance between successive crests. Frequency rises as wavelength falls; producing fewer waves each second gives a longer wavelength.

A mechanical wave passes through a medium, such as water, air or a rope. Parts of that medium oscillate about their equilibrium positions and pass the disturbance to neighbouring parts; they do not travel all the way from the source to the receiver.