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.
(i) What change takes place in the sound to give this idea?
(ii) What causes the change in the sound?

Answer 1

(i) The frequency of sound to increases $(f\propto \frac{1}{l})$ when the length ($l$) of the air column is decreased, i.e., when the bucket is getting filled with water.
(ii) Change in sound is caused because air column is decreased on the filling the water in bucket.