Describe in brief, with the aid of a sketch diagram, an experiment to demonstrate that a material medium is necessary to transmit sound.
The sketch diagram of bell jar is:
Take an airtight bell jar having an arrangement of the electric bell as shown above in the diagram. The electric bell is suspended inside the glass bell -jar, which is further connected to the vaccum pump. When the circuit of the electric bell is completed, the hammer strikes the gong repeatedly and sound is heard. Now, start withdrawing the air from the glass bell -jar using the vacuum pump and loudness of the sound will keep decreasing. When the whole of the air is withdrawn, no sound will be heard. So, this experiment shows that a material medium is needed for the propagation of sound.