The Glass shattering experiment
Weakening glass' intermolecular structure
This Quicktime movie shows the classical shattering of a wine glass when in resonance using a 5 Watt sine wave audio tone in the range of 800Hz. Play the movie and watch carefully the motion of the glass rim. You will see that the radius of the rim of the wine glass is actually deforming by as much as 5 mm!! There is no way that such thing could be done under non resonant conditions without heating up the glass in a furnace. At room temperature, the glass is normally so brittle that it would shatter as soon as the rim is deformed by 1 or 2mm. This 'jellification effect' indicates that resonance weakened the actual intermolecular force and made them similar to those within liquids, thus inreasing the elasticity of glass. So, the audio energy in this experiment is used to modify the solid state of glass into the next higher state of matter, to give it liquid state characteristics, making it more elastic. At this point I have to point out that there is no overunity here.
In an oscillating system at resonance, one pours power in small amounts, but the energy thus transferred gets accumulating in the system (actually in the standing wave). It is a common misperception to think that with few energy we produce lots of work. We just keep accumulating slowly the energy, by putting a little power over a relatively long time, and then we release the same amount of energy in a relatively short time, giving a tremendous energy per unit time, that is power. Same applies to sonoluminiscense and all other resonance phenomena mentioned here.
How to conduct the experiment
This demonstration requires a fair amount of equipment. A 10Watt stereo amplifier, whose output goes to a horn driver near the wine glass to be broken, can be switched between a frequency generator, easily tuned through a broad spectrum, a video camera, and a frequency synthesizer which can generate a very accurate frequency, at about 0.1Hz steps. Alternatively, if your frequency generator is of the digital type and accurate to 0.1Hz and is powerful enough, you can use it instead of the synthesiser. The response of the wine glass to the sound is monitored with a microphone connected to an oscilloscope. The first four steps can be prepared before the lecture, but most instructors like to run through them with the class so the students can see the entire operation.
1.. Flick the wine glass with you finger to "ring" it. With the amplifier set at low hearing volume, tune the frequency generator until you hear a similar pitch.
2.. Watching the response on the scope, tune the frequency generator until you hit the resonance of the wine glass where the signal on the oscilloscope becomes much larger.
3.. Read off the approximate resonance frequency from the frequency counter and enter this number on the frequency synthesizer. Switch the amplifier over to the frequency synthesizer input.
4.. With the synthesizer in the "edit" mode, change the frequency one hertz at a time until you hit the resonance again. Now tune by tenth hertz until you reach the maximum peak.
5.. Move the microphone away from the wine glass and place the Plexiglas shield in front (to prevent broken glass from spraying into the class and the video camera).
6.. Start video recording and turn up the amplifier volume to quite loud and the glass will break. The sound is loud, but not painful to the operator. At the position of the glass, it is approximately 140 dB. View video in slow motion to see what's happening.