A mechanical wave is a wave that is an oscillation of matter, and therefore transfers energy through a medium. While waves can move over long distances, the movement of the medium of transmission—the material—is limited. Therefore, the oscillating material does not move far from its initial equilibrium position. All of the options are mechanical waves except radio wave which is an electromagnetic wave of a frequency between about 10⁴ and 10¹¹ or 10¹² Hz, as used for long-distance communication.