The effect of sound on a bubble: a KS3/4 physics lesson starter This short clip is ideal for use as a lesson starter in KS3/4 science and features a demonstration of how sound needs a medium to pass through.

The presenter attaches a sound generator to a loudspeaker. He holds a bubble in front of the speaker, and turns the volume down and up. At low volume, the bubble moves slowly. At high volume, the bubble wobbles a lot.

The question for students to answer is: What makes the bubble move?

See the accompanying teachers’ notes for a full explanation of the science underpinning the demonstration, plus suggested extension activities.

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