Question

Write an activity each to show that sound needs a medium to travel
1.in solids
2.in liquids

Answer 1

Take a jar and connect it with a vaccum pump.

Place an electric bell inside this jar such that it doesn't touch any part of the jar. You can hang it using fine strings.

Now, switch on the bell and start the pump so as to remove air from it.

You will observe that the sound gets fainter with time and is inaudible at the moment when all of the air is removed from the jar.

This proves that sound requires medium to travel.

For liquids :

Place a squeaking toy or sound making toy in a polythene bag and immerse it in a bucket full of water.

If we put our ear to the side of this bucket and press the toy, we can hear the sound of squeaking toys clearly.

The sound of squeaking toy comes to ear through water contained in the bucket.

This shows that sound can travel through water.