Transverse and Longitudinal Waves

Figure 1.1: Example of displacements in transverse and longitudinal waves. The wave motion is to the right as indicated by the large arrows. The small arrows indicate the displacements at a particular instant.

With the exception of light, waves are undulations in some material medium. For instance, ocean waves are (nearly) vertical undulations in the position of water parcels. The oscillations in neighboring parcels are phased such that a pattern moves across the ocean surface. Waves on a slinky are either transverse, in that the motion of the material of the slinky is perpendicular to the orientation of the slinky, or they are longitudinal, with material motion in the direction of the stretched slinky. (See figure 1.1.) Some media support only longitudinal waves, others support only transverse waves, while yet others support both types. Deep ocean waves are purely transverse, while sound waves are purely longitudinal.