Waves:

In physics a wave is a oscillation or disturbance that travels through space time, accompanied by a transfer of power. Wave motion transfers energy from one end to another, often with no permanent displacement of the particles of the medium-that is, with little or no related mass transport. They consist, instead, of vibrations or oscillations around almost fixed locations. Waves are defined by a wave equation which sets out how the disturbance proceeds over time. The mathematical form of that equation varies relaying on the type of wave.

There are two basic types of waves. Mechanical waves travel through a medium, and the element of this medium is deformed. The deformation reverses itself taking to restoring forces resulting from its deformation. For example, sound waves travel via air molecules colliding with their neighbors. When air particles collide, they also bounce away from one other (a restoring force). That keeps the molecules from continuing to go in the direction of the wave.

The second basic type of wave is electromagnetic waves, do not need a medium. As a substitute, they consist of periodic oscillations in magnetic and electrical fields generated by charged particles, and may therefore travel through a vacuum. These kinds of waves vary in wavelength, and add radio waves, microwaves, visible light, X-rays, infrared radiation, gamma rays and ultraviolet radiation.