Electro-Magnetic (EM) energy is made up of both particles and waves. A single wavelength is 2¼ or 360° of the wave's angular distance. When a wave travels through a material, the wavelength is the distance travelled through the material by 2¼ of a wave.
The number of times a wave oscillates over a certain amount of time is know as the frequency of the wave. The units of frequencies are Hertz (Hz) which is the number of complete wavelengths that pass a point in a single second. Therefore, 1 Hz = 1 cycle/second or 1/s.
The wavelength of a signal passing through a material depends on the frequency (f ) of the wave and the signal velocity (u ) through the material (a property of the material itself). As shown above, the units of frequency are 1/s, and the units of velocity are m/s. Since wavelength(l ) is measured in m, the equation to obtain wavelength is:
l = f * u
or wavelength = frequency * velocity
A higher amplitude wave of a given frequency carries more energy than a low amplitude wave. A signal can be detected only if its amplitude is greater than that of any background noise. For example, if you are listening to a radio in New York City, you can pick up a station from Seattle only if its signal is stronger than the EM noise caused by the sun, electric motors, local radio stations, etc.
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Updated: August 03, 2011
© 1998, Brian C. Welch,
Univ. of Wyoming