Resonance
Definition #
Resonance refers to a tendency of a system to oscillate more at certain frequencies than at others. Those frequencies are known as resonant frequencies.
(Photo: Steven Duong on Flickr)
Commentary #
An excellent example of acoustic resonance is shattering a wine glass with sound. Here's a quick explanation as to why the glass shatters:
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The sound is being generated by a speaker. The speaker works by moving a small cone back and forth generating the appropriate frequency. You can sometimes see the movements.
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Many frequencies make the glass vibrate, but only a handful make it vibrate so much that it cannot stay together. Those frequencies are the resonant frequencies—they make the glass vibrate (i.e. oscillate) much more than the other frequencies.
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Since the glass is insufficiently elastic, it shatters.
Meta #
What other resonant systems have you encountered?