The medium does not move: the disturbance does
One of the most common confusions about waves is believing that “something goes from A to B”. In reality, in a wave on the sea, the water does not travel with the wave: every point on the surface performs small vertical oscillations, and it is the state of oscillation that propagates from one point to the next. The cork never reaches the shore: it bobs up and down as the waves pass beneath it. This observation has profound implications: waves carry energy and momentum without carrying matter. And it is precisely for this reason that they can cross empty space (electromagnetic waves) or be used to transmit information (sound, radio, light): the signal travels, but the medium remains on average still.
Collegamenti
Argomenti: Waves Concetti: Harmonic wave
Esercizi collegati: Problem — Dimensional analysis of the speed on a string · Problem — True or false on waves and Doppler · What a wave carries (the leaf)