The fans never move out of their seats, they only move up and down. The wave comes from the sychronized motion of many people , which creates a disturbance that moves around the stadium. This would not have been the case if everybody moved out of synch. In this Chapter we learn some basics about how to characterize and describe wave motion. Let us first discuss some different kinds of waves.
Waves can propagate either through a medium or in vacuum.
In the case of mechanical waves , a material medium is disturbed. Originally physicists thought that waves can only form inside a material medium. After Einstein it became clear that light waves propagate inside the vacuum and are examples of electromagnetic waves . Waves can also be classified as transverse or longitudinal. Transverse waves cause the medium particles to move in a direction perpendicular to that of the wave propagation.