What is a Wave?
Imagine tossing a pebble into a calm lake. Ripples spread outward in perfect circles — but the water molecules themselves don't travel across the lake. Instead, they bob up and down while the disturbance (and its energy) moves outward. This is the essence of a wave.
A repeating disturbance or oscillation that transfers energy from one point to another without permanently displacing the particles of the medium through which it travels.
Waves are everywhere in physics:
- Sound reaching your ears from a speaker
- Light arriving from the Sun
- Seismic waves travelling through the Earth during an earthquake
- Radio signals connecting your phone to a network
The single most important idea about waves: they transfer energy, not matter. The medium's particles oscillate about their equilibrium positions — they do not travel with the wave.
Waves can travel through a medium (mechanical waves) or through a vacuum (electromagnetic waves). This distinction will become important as we look at different wave types.