Physics KS3 / GCSE: Resonant Frequency

Dr Kevin Fong explains how sound waves could pose a real threat to astronauts and rockets in space.

He uses the example of the Soyuz Rocket, and explains that as it travels through the atmosphere, the air pressure can pose a number of dangers.

One of these threats comes from vibrations, i.e. sound. When the sound waves are at the resonant frequency of the rocket, vibrations could destroy it.

Kevin first uses a girl from the audience and then Lucy, the producer of the Lectures, who both in turn have to listen to the resonant frequency of a wine glass and then sing it back into a microphone.

The microphone is connected to a loudspeaker below the wine glass, which eventually resonates and shatters when the correct frequency is sung.

This clip is from the Royal Institution Christmas Lectures 2015.

Teacher Notes

You could ask students if they have heard about the phenomenon where a wine glass is shattered by an opera singer. Ask them if they have seen this.

After watching the clip, ask them to suggest why the woman succeeded in breaking the glass but the girl did not.

This could be due to the higher amplitude (loudness) of the woman’s voice, or perhaps a pitch more closely matched to the resonant frequency of the glass.

Curriculum Notes

This clip will be relevant for teaching KS3 and GCSE Physics.

This topic appears in OCR, Edexcel, AQA, WJEC KS4/GCSE in England and Wales, CCEA GCSE in Northern Ireland and SQA National 4/5 in Scotland.

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