| Progressive waves | Stationary waves |
| The disturbance produced in the medium travels onward, it being handed over from one particle to the next. Each particle executes the same type of vibration as the preceding one, though not at the same time. | There is no onward motion of the disturbance as no particle transfers its motion to the next. Each particle has its own characteristic vibration. |
| The amplitude of each partide is the same but the phase changes continuously, | The amplitudes of the different particles are different, ranging from zero at the nodes to maximum at the antinodes. All the particles in a given segment vibrate in phase but in opposite phase relative to the particles in the adjacent segment. |
| No particle is parmanently at rest. Different particles attain the state of momentary rest at different instants, | The particles at the nodes are permanently at rest but other particles attain their position of momentary rest simultaneously. |
| All the particles attain the same maximum velocity when they pass through their mean positions. | All the particles attain their own maximum velocity at the same time when they pass through their mean positions. |
| In the case of a longitudinal progressive wave all the parts of the medium undergo similar variation of density one after the other. At every point there will be a density variation. | In the case of a longitudinal stationary wave the variation of density is different at different points being maximum at the nodes and zero at the antinodes. |
| There is a flow of energy across every plane in the direction of propagation. | Energy is not transported across any plane. |
Note :
In the above discussions, while dealing with the interference of waves, it has been assumed that the principle of superposition holds good. Not all waves obey this principle. For e.g., large amplitude waves in fluids and solids interact in a complicated non-linear fashion, Thus, shock waves generated by jet aircrafts and ocean surf do not obey this principle. In general, only experiments can determine whether or not the principle is applicable to a given situation. It has been found that the smaller the amplitudes of the waves, the more precisely valid is the principle of superposition. This is true because a small-amplitude wave does not alter the properties of a medium to a large extent.