Question

14) Site an experiment to show sound needs a material medium for its propagation

Answer 1

#Take a glass bell jar, connect it with vacuum pump and suspend an electric bell in it.#Connect electric bell with a battery.#Switch on the electric bell and hear the sound of bell.#Now remove the air completely from the bell jar using vacuum pump and observe the sound of electric bell.{propagation of sound experiment class nine scinece cbse ncert}

Answer 2

Experiment:

Materials required: A stand, a mobile phone, a vacuum pump, a glass jar, a table and some Vaseline.

Method:

On a table, place mobile phone on a stand.

Make a hole beside the stand and fix a vacuum pump on the lower side such that the air from the upper side can be sucked out.

Make the hole airtight using Vaseline ( do not block the opening of the pump).

Place an inverted glass jar over this setup and make it air tight using Vaseline again.

Call on the mobile phone and listen to the ring.

Now start the vacuum pump.

After most of the air is sucked out, call on the mobile phone again.

Observation: You will notice that the loudness of the Ring has decreased considerably.

Conclusion: This proves that sound requires a medium to propagate.