Waves can be characterized by the following four characteristics: amplitude, wavelength, frequency, and speed. A mechanical wave is a disturbance in matter that transfers energy from place to place. A mechanical wave starts when matter is disturbed. Consider what happens when a drop of water falls into a pond. This disturbs the water in the pond. Then the disturbance travels outward from the drop in all directions. This is the wave. A source of energy is needed to start a mechanical wave. In this case, the energy comes from the falling drop of water.     The energy of a mechanical wave can... Show more

Waves can be characterized by the following four characteristics: amplitude, wavelength, frequency, and speed.

A mechanical wave is a disturbance in matter that transfers energy from place to place. A mechanical wave starts when matter is disturbed. Consider what happens when a drop of water falls into a pond. This disturbs the water in the pond. Then the disturbance travels outward from the drop in all directions. This is the wave. A source of energy is needed to start a mechanical wave. In this case, the energy comes from the falling drop of water.    
The energy of a mechanical wave can travel only through matter. This matter is called the medium (plural, media).    
The medium in the example just described is a liquid—the water in the pond. But the medium of a mechanical wave can be any state of matter, including a solid or a gas. It's important to note that particles of matter in the medium don't actually travel along with the wave. Only the energy travels. The particles of the medium just vibrate, or move back-and-forth or up-and-down in one spot, always returning to their original positions. As the particles vibrate, they pass the energy of the disturbance to the particles next to them, which pass the energy to the particles next to them, and so on.    

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