A comparison is made between wave patterns in dispersive and nondispersive media on the basis of the interference patterns of two sine waves. The sine waves are assumed to be of equal amplitude and to have a common direction of propagation. For the dispersive medium, it is shown that the wave pattern observed as time varies at a given position is not the same as that found when considered as position changes for an instant of time. For corresponding intervals of space and time it is found that the snapshot contains a different number of individual oscillations than the sample at a single location. The difference is seen to increase as the component frequencies become more nearly the same.