When you blow over the mouth of a bottle or pluck the string of a guitar, you create a standing wave. That wave will always produce the same sound or pattern. Here’s an easy way to show how it works. This Standing Wave Demonstrator uses your power drill. Simply attach the demonstrator crank to any power drill, anchor the free end of the 4.5m string to a stationary object, and turn the drill on. By adjusting the tension on the demonstrator you can produce successive harmonics and nodes. Change the tension, the speed and the distance-then have your students predict the results.
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