Characteristics of Stationary Waves

Five general characteristics distinguish a stationary (standing) wave from an ordinary progressive (travelling) wave. First, a stationary wave is confined between two rigid boundaries and is characterised by the disturbance appearing fixed in place -- unlike a progressive wave, it does not itself advance forward or backward through the medium, which is precisely why it is called "stationary" or "standing". Second, certain fixed points within the region occupied by the wave show maximum displacement amplitude, called anti-nodes, while other fixed points show minimum or exactly zero displacement amplitude, called nodes -- a contrast with a progressive wave, in which every particle shares the identical vibration amplitude. Third, consecutive nodes (or consecutive anti-nodes) are always separated by exactly $\lambda/2$. Fourth, a node and its immediately neighbouring anti-node are always separated by exactly $\lambda/4$. Fifth, and perhaps most importantly from an energy standpoint, a stationary wave transports absolutely no net energy along the medium at all -- energy simply sloshes back and forth locally between neigh …