A wave is a disturbance that travels either through a medium (mechanical waves, such as sound waves) or through space (electromagnetic waves, such as light waves). As a wave travels, it carries energy from one place to another. Waves are used to describe phenomena such as sound, light, and the behavior of particles.

Some waves require a medium in order to propagate. This means that certain waves must actually have physical contact between particles in order to transfer kinetic energy, the energy of motion. These waves are called mechanical waves. In a mechanical wave, a disturbance causes a portion of the medium to deviate from an equilibrium (resting) position. Because it is physically connected to a nearby portion, it causes the nearby portion to deviate from its equilibrium position, but because the influence is by means of a force, the new portion accelerates rather than moves instantaneously. The...