Waves
Overview of waves

Webster's dictionary defines a wave as shown in Figure .

The most important part of this definition is that a wave is a "disturbance or variation" that travels through a medium. The medium through which the wave travels may experience some local oscillations as the wave passes, but the particles in the medium do not travel with the wave. The disturbance may take any of a number of shapes, from a finite width pulse to an infinitely long sine wave.

At many sporting events, fans will perform an activity referred to as the wave. The wave is formed by a group of people jumping up and sitting back down. Some nearby people see them and they jump up, some people further away do the same thing and soon there is a wave traveling around the stadium. The wave, or the action of people jumping up and sitting back down, is the disturbance, and it travels around the stadium. However, none of the individual people in the stadium are carried around with the wave as it travels. They all remain at their seats.

Longitudinal sound waves in the air behave in much the same way. As the sound wave passes through, the particles in the air oscillate back and forth from their equilibrium positions but it is the disturbance that travels, not the individual particles in the medium. The first interactive activity illustrates this concept.

Transverse waves on a string are another example. The string is displaced up and down, as the wave travels from left to right, but the string itself does not experience any net motion. This is shown in the second interactive activity.


Interactive Media Activity

Interactive Activity: Longitudinal Pulse

This activity demonstrates how sending longitudinal pulses can be close or far apart.

Interactive Media Activity

Interactive Activity: Transverse Pulse

This activity demonstrates an interactive transverse pulse.