Shown above is a representation of two sources of sound-- a smapshot in time of what they
may look like. You can image them as two tuning
forks, for instance-- one leading to the red waves, and the second leading to the blue waves.
If this is a bit confusing, go and study the representation of a single source.
Note that this is not the true interference pattern, as these waves are being drawn
on top of each other, but not added together. However, we can already see some interesting
things: across the middle of the picture (horizontally), notice how all the crests of the red waves
line up with the crests of the blue waves, as do their troughs.
This is constructive interference: here the two waves
will add together, reinforcing each other. We also see that happening across the middle of the
picture, vertically: here the two waves are moving in slightly different directions, but down the center
we always have the red crests overlapping the blue crests, and the red troughs overlapping the
blue troughs, so this is again constructive interference. The next picture makes these things
easier to see...
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