Stationary vs Progressive Waves
Stationary vs Progressive Waves
- A stationary wave does not travel, so it cannot carry energy away. Every difference below comes from that one fact.
- The exam often asks how a stationary wave differs from a normal (progressive) wave. Three things separate them: energy, amplitude and phase.
The differences, side by side
| Feature | Progressive wave | Stationary wave |
|---|---|---|
| Energy | carried along, point to point | no net energy carried along |
| Amplitude | the same at every point | zero at nodes, biggest at antinodes |
| Wavelength | one clear wavelength | same wavelength as the two waves that make it |
| Phase | changes smoothly point to point | same across a loop; opposite in the next loop |
Phase along the wave
- The stretch of wave between two neighbouring nodes is called a .
- Within one loop every point moves in step. They all reach their peak together and pass through zero together. They are in phase.
- The next loop moves the opposite way. When one loop is up, its neighbour is down. Neighbouring loops are in antiphase (180° apart).
Your turn— tap to reveal the worked answer (9702-style)
Two points sit in the same loop of a stationary wave. State their phase difference.
Answer: 0° — points in the same loop move in phase. Points in neighbouring loops would be 180° apart (antiphase). (9702-style)