Physics 2010 JAMB Past Questions - Question 25: The sound of an electric bell dies down slowly when air is slowly pumped out from a bottle because

Correct Answer

D

Explanation

The sound of an electric bell dies down slowly when air is slowly pumped out from a bottle because the transmission of sound relies on the presence of a medium, typically air, for the sound waves to travel through. Here's what happens when air is slowly pumped out from a bottle:

1. Initially, when the bell is rung, it produces sound waves that propagate through the air in the bottle.

2. As air is pumped out of the bottle, the density of air within the bottle decreases. Sound waves require a medium with a certain density to travel effectively. When the density of the medium decreases, sound waves encounter less resistance and become less efficient at propagating through the reduced-density air.

3. The sound waves gradually lose energy as they encounter fewer air molecules to interact with. This leads to a decrease in the amplitude of the sound waves, causing the sound to become quieter.

4. With continued removal of air from the bottle, the sound waves become weaker and eventually dissipate to the point where they are no longer audible.

In summary, the sound of the electric bell dies down slowly as air is pumped out because the reduced air density inside the bottle makes it more difficult for sound waves to propagate, causing them to lose energy and gradually fade away.