What Are Waves? The Physics of Repeating Motion

Waves are repeating disturbances that transfer energy without permanently moving matter.
They come in two main types: mechanical (sound, water) and electromagnetic (light, radio).
Mechanical waves need a medium—like air, water, or solids—to travel.
Electromagnetic waves don’t need matter; they move through the vacuum of space.
The crest is the highest point of a wave, while the trough is the lowest.
Wavelength is the distance between two crests, and frequency is how many pass each second.
Amplitude measures wave height and tells us how much energy it carries.
In transverse waves, particles move up and down; in longitudinal waves, they move back and forth.
Waves can reflect, refract, diffract, and interfere—bending and combining in surprising ways.
From ocean tides to Wi-Fi signals, waves are nature’s universal language of motion and energy.