Progressive wave
● VERBATIM — examined word-for-wordThe propagation of a disturbance which transfers energy (and momentum) from one point to another by means of oscillations/vibrations, without the physical transfer of matter — particles only oscillate about fixed equilibrium positions.
What this actually means
The wave is the pattern, not the stuff. Watch a leaf floating on a pond when a ripple passes: the ripple travels across the water, but the leaf only bobs on the spot. Energy rides the pattern from particle to particle; no particle ever travels with it.
Examiners want three ingredients: energy (and momentum) is transferred, the transfer happens through oscillations, and no matter travels along. Miss any one and the definition mark is gone.
Common slip: writing 'the particles move along the wave'. They never do. Each particle oscillates about its own fixed equilibrium position and hands the motion to its neighbour, like a stadium wave passing through seated fans.
Writing that particles travel along with the wave — they only oscillate about fixed positions.
Prove it — watch it be true
- Press play and watch the ghost profile sweep along the chain
- Pick any bead: its horizontal position never changes, it only bobs up and down
- That is the definition in one view: the shape (energy) travels, the matter stays put