An alarm bell is kept inside a vessel as shown in the below figure. A person standing close to it can distinctly hear the sound of the alarm. Now if the air inside the vessel is removed completely how will the loudness of alarm get affected for the same person?
T
Air is removed through the tube
Alarm clock
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Solution
Propagation of sound:
Sound is a sequence of waves which require a material medium to travel.
It can travel in solid-liquid or gas and have different velocities for different mediums.
But sound cannot travel in a vacuum, as the vacuum is completely devoid of any material. So, the sound doesn't get a medium to travel.
Affect on the person:
When the air from the vessel is removed completely, it becomes a vacuum and sound cannot travel through it.
Since there will be no sound propagation in the vessel, the man standing outside also will not hear anything.
Hence, the man would not be able to hear the alarm sound.
Fig. (a)
