Cite an experiment to show that …

• Sound Needs a Medium for Propagation:

The substance through which sound travels is called medium. The medium can be solid, liquid or a gas. Sound needs a medium for propagation means it needs a solid, liquid or gas for transmission. Sound can travel through solids, liquids and gases but it cannot travel through vacuum as it has no molecules which can vibrate and carry sound waves.

Take a ringing electric bell and place it inside an airtight glass jar. We can hear the sound from it as air is present in it and sound can travel through air.

Now, if we place the ringing bell in a glass jar containing a vacuum pump, the sound becomes fainter and fainter as air gradually removes from it. When all the air is removed from the glass jar, no sound can be heard. This shows that sound cannot travel through vacuum.