Question

A bucket kept under a running tap is getting filled with water. A person sitting at a distance is able to get an idea when the bucket is about to be filled.

What change takes place in the sound to give this idea?

Answer 1

1. When a bucket is kept under a running tap to fill it with water, a person sitting at a distance will be able to hear the sound of the water getting shriller as the bucket fills due to the following two reasons
2. When the length of the air column decreases the frequency of sound increases.
3. Relation between the length of air column and frequency is given by,
   $f\propto \frac{1}{l}$ (both are inversely proportional)
   Where, $f$ is the frequency and $l$ is the length of the air column.

As a result, the person sitting at a distance will be able to get an idea of when the bucket is about to be filled.