Describe an activity to show that sound requires a material medium for its propagation.

Activity to Show That Sound Requires a Material Medium for Propagation

Aim: To demonstrate that sound cannot travel through a vacuum and requires a material medium for its propagation.

Materials Required:

An electric bell
A glass bell jar
A vacuum pump
Procedure:

Take an electric bell and place it inside a glass bell jar. Ensure the bell is connected to an external power source so that it can be activated when required.
Seal the bell jar to make it airtight.
Initially, let the air remain inside the bell jar. Turn on the electric bell. Observe the sound produced by the bell.
Now, connect the bell jar to the vacuum pump. Gradually remove the air from the jar by using the vacuum pump.
As the air is evacuated from the jar, observe the sound of the bell.
Observations:

When the air is present in the bell jar, the sound of the electric bell is clearly audible.
As the air is removed using the vacuum pump, the intensity of the sound decreases.
When the jar becomes almost a complete vacuum, the sound of the bell is no longer heard, even though the bell continues to ring (as seen visually).
Conclusion:
This activity demonstrates that sound requires a material medium, such as air, for its propagation. In the absence of a medium, such as in a vacuum, sound cannot travel.