Question

Can sound travel through a vacuum ? Describe an experiment to explain your answer.

Answer 1

Experiment — Arrange an electric bell, a glass bell jar, a vacuum pump, a battery and a switch as shown in the figure. When the circuit is closed by pressing the switch, the bell starts ringing and sound can be heard. Now remove the air from the jar with the help of vacuum pump. The loudness of the sound gradually decreases and a stage comes when no sound is heard. Sound requires a medium to travel but cannot travel in vacuum.

Connect the bell to a battery through a switch. On pressing the switch, the bell starts ringing and a sound is heard. The sound reaches us through the air in the jar.
Now start the vacuum pump. It withdraws the air from the jar. You will notice that as the jar is evacuated, the sound becomes feeble and feeble. After some time when no air is left within the jar, no sound is heard. However, the hammer of the electric bell can be still seen striking the gong. The reason is that when no air is left in the jar, the sound does not reach us, although the bell is still ringing (or vibrating).
Thus, sound cannot travel through a vacuum.