Question

Cite an expirement to show that sound waves need a material medium for their propagation

Answer 1

Answer:

the answer is as follows

Explanation:

By the following experiment it shows sound cannot travel through vacuum. It needs a medium to propagate.

Apparatus: - Electric bell, Airtight glass bell jar, Switch, vacuum pump.

Procedure: -

Take an electric bell and an airtight glass bell jar. The electric bell is suspended inside the airtight bell jar.

If we press the switch ’ON’ we will be able to hear the bell.

Now when we connect the bell to the vacuum pump. All the air from the jar is pumped out gradually; the sound becomes fainter, although the same current is passing through the bell.

After some time when more air is pumped out from the jar, we will hear a very feeble sound.

And finally the sound will not be heard when all the air is completely removed from the jar.

This happens as almost all air has been pumped out.

This proves sound needs a material medium to propagate, it can’t propagate through vacuum.

Physics Class 9 Sound Bell Jar Experiment

Answer 2

The activity is as follows :-

Take an empty vessel or glass. suck air out of it. now place a cell phone in it and cover the mouth of the glass. now from another mobile phone give a missed call to it.

we see that we cannot hear the sound of the ring as the mouth of the glass is covered and air which is the medium for sound propagation is not present. we call it a vacuum.

now, remove the cell phone out of glass & give a missed call.

we can now hear the sound of ring as there is air for propagation of the sound.

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