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


To prove that sound needs a medium for propagation, we do the Bell Jar experiment


In this experiment -

  • We take an electric bell and an airtight glass jar
  • The electric bell is suspended on the glass jar
  • And the glass jar is connected to a vacuum pump from the bottom
  • Now, we switch on the bell
  • We can hear the sound bell. 
  • Now start the vacuum pump. The air inside is pumped out gradually
  • And we can observe that the sound becomes fainter and fainter.
  • Eventually, when there is no air inside the jar, we cannot hear the sound of the bell


Thus, when vacuum is created in the glass jar, then the sound of ringing bell cannot be heard.

This shows that sound needs a medium for propagation and cannot travel through vacuum.

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Maninder Singh

CA Maninder Singh is a Chartered Accountant for the past 14 years and a teacher from the past 18 years. He teaches Science, Economics, Accounting and English at Teachoo