Name: Study of Infrasound and Ultrasound in Waves
Uploaded: 2019-07-19
Duration: 5 min 55 s
Description: If you pay attention, you will be able to hear so many different sounds in your daily life. What about the sounds that the human ear is not capable of detect...

Question

Describe in brief, with the aid of a labelled diagram, an experiment to demonstrate that a material medium is necessary for the propagation of sound.

Accepted Answer

Experiment —

Take an electric bell and an air tight glass bell jar. The electric bell is suspended inside the bell jar. The bell jar is connected to the vacuum pump as shown below.

Observation: When the switch of the electric bell is completed by pressing the key, the hammer of the electric bell strikes the gong repeatedly and the sound of the bell is heard.

Now keeping the key pressed, the air is gradually taken out from the jar by the vacuum pump. It is noticed that the loudness of sound goes on decreasing as the air is taken out from the bell jar and finally no sound is heard when the entire air from the jar has been drawn out.

The hammer of the electric bulb is still seen striking the gong repeatedly which means that the gong is still vibrating to produce sound (as the hammer strikes the gong), but it is not heard.

Explanation —

When the hammer of the bell hits the gong, the sound is produced due to the vibration of the gong which travels through the air to the wall of the jar. This causes the wall of the jar to vibrate due to which the air outside the jar is also set in vibration. Thus, the sound is heard by us. But when air has been removed from the jar, the sound produced due to vibrations of the gong could not travel to the wall of the jar, so the wall could not vibrate and no sound is heard.

This clearly demonstrates that a medium is required to propagate the sound.

Describe in brief, with the aid of a labelled diagram, an experiment to demonstrate that a material medium is necessary for the propagation of sound.

Important Questions on Propagation of Sound Waves

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