Experiment to show sound cannot travel through a vacuumThis classic experiment is beautifully illustrated in this mini-vidclip: A bell can be heard ringing within a bell jar. The bell jar is connected to a vacuum pump and the air is slowly removed. Once a vacuum (no air particles) has been achieved, the pump is turned off and air is allowed to slowly re-enter the bell jar. To obtain a full vacuum is very difficult (and involves expensive equipment!). This experiment in a lab will probably achieve 95% vacuum - but that is enough to see the effect. The following video is a really old one - but the type of bell used was useful as you could actually see that the clanger was still moving when the sound was no longer audible. |
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