A disturbance or variation that transfers energy progressively from point to point in a medium and that may take the form of an elastic deformation or of a variation of pressure, electric or magnetic intensity, electric potential or temperature. Particles move in direction of energy flow.
Particles move perpendicular to the direction of energy flow.
The number of cyclic events that occur in a given time period. The distance between two adjacent bands of compression or rarefaction. The speed at which the wave moves through the medium. Also called the speed of propagation. Energy - the pressure in the medium or the strength of the electrical signal generated by the returning echo.