Question

Cite an experiment to show that sound needs a material medium for its propagation :

Answer 1

Apparatus required:

A strong jar, Electronic Bell, Cork, Vacuum pump.

Procedure:

Take an electronic bell and connect it to electrical supply. You should hear the bell ringing. This confirms that the bell is working. Now, take a jar and make a small hole in the bottom and insert a small pipe through it. Connect the other end of the pipe to a vacuum cleaner. Make a very small hole in the cork (just enough to insert wires) and insert wires connected to the electronic bell. Fit the cork as shown in the figure. Turn on the bell and the vacuum cleaner. You will observe no sound is heard.

Conclusion:

Since the bell was working but its sound could not be heard outside the jar when air was pumped out, it can be concluded that sound needs a medium for propagation.