http://www.ck12.org Chapter 5. Energy
5.22 Mechanical Wave
- Describe mechanical waves.
- Define the medium of a mechanical wave.
- Identify three types of mechanical waves.
No doubt you’ve seen this happen. Droplets of water fall into a body of water, and concentric circles spread out
through the water around the droplets. The concentric circles are waves moving through the water.
Waves in Matter
The waves in the picture above are examples of mechanical waves. Amechanical waveis a disturbance in matter
that transfers energy through the matter. A mechanical wave starts when matter is disturbed. A source of energy is
needed to disturb matter and start a mechanical wave.
Q:Where does the energy come from in the water wave pictured above?
A:The energy comes from the falling droplets of water, which have kinetic energy because of their motion.
The Medium
The energy of a mechanical wave can travel only through matter. The matter through which the wave travels is called
themedium(plural, media). The medium in the water wave pictured above is water, a liquid. But the medium of a
mechanical wave can be any state of matter, even a solid.
Q:How do the particles of the medium move when a wave passes through them?
A:The particles of the medium just vibrate in place. As they 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. Particles of the medium don’t
actually travel along with the wave. Only the energy of the wave travels through the medium.