When two EM waves occupy the same space, their effects combine to form a new
wave of a different shape. For example, air pressure changes caused by two
sound waves add together. The electrical and magnetic forces caused by two
light waves or two radio waves are also added together.
Jean Baptiste
Fourier is responsible for one of the great mathematical discoveries. He proved
that a special sum of sine waves, of harmonically related frequencies, could be
added together to create any wave pattern. Harmonically related frequencies are
simply frequencies that are multiples of some basic frequency. Complex waves
can be built out of simple waves. Another way of stating this is that any
repeating wave is mathematically and physically equivalent to the result of
adding just the right collection of sine waves together. This sum is known as a
Fourier series.
Use the interactive activity to create multiple sine
waves and a complex wave that is formed from the additive effects of the
individual waves.
Finally, a square wave, or a square pulse, can be
built by using the right combination of sine waves. The importance of this will
be clarified when modulation is discussed.