Transport of Energy Through Waves : Energy Transfer Medium

TRANSPORT OF ENERGY: WAVES 

Energy can be moved from place to place, and thus it must be transported in some form. Waves are one way of transporting energy. What is a wave? It is the transport of a disturbance; that is, a wave is a disturbance that moves. How does this account for the transport of energy? Imagine that two people several feet apart hold the ends of a rope; when one jiggles the rope, a wave will travel from one end to the other. No par­ticles are moving from one end of the rope to the other, but a disturbance is traveling along it. We know that energy is transported by the disturbance since, when the distu rbance arrives, the receivi ng hand is jiggled. That is, the wave in the rope does work on the hand, giving it kinetic energy. Another example of a wave is the disturbance that propagates across the surface after a stone is dropped into a pond. A Wave can thus be defined as a disturbance capable of trans­ferring energy from one place to another. 

To understand waves better, consider how sci­entists describe them quantitatively. The distance between successive crests or troughs is called the wavelength. The number of complete cycles of the disturbance passing a fixed point per sec­ond is called the frequency. The speed of the waves the distance it travels per unit of time; this is just the length of each wave (its wavelength) multiplied by the number of waves passing a fixed point per unit of time (its frequency). Thus the speed of the wave is the product of its wavelength and frequency. The last quantity used to describe a wave is its amplitude. This is the greatest height the crests reach or the greatest depth to which the troughs fall. The greater the ampli­tude, the more energy the wave transports from one to another. In fact, the energy of the wave is measured by the amplitude squared. 

Waves are one means of transporting energy but, as we have mentioned, not the only one: The collision of bodies is another way to transfer energy and thus transport it from one place to another. The best com­mon example of this process is the behavior of atoms and molecules in a gas. Therefore let us next focus the ssion of motion on the world of the atom.