Question

What frequency changes do you observe when a water-bottle is filled under a tap?

• A. The intensity of the sound keeps increasing as the amplitude of vibration keeps increasing
• B. The pitch of the sound keeps increasing as the length of the vibrating air column keeps decreasing
• C. The pitch of the sound keeps decreasing as the length of the vibrating air column keeps decreasing
• D. The pitch of the sound keeps decreasing as the length of the vibrating water column keeps decreasing
• E. The pitch of the sound keeps increasing as the length of the vibrating air column keeps increasing

Answer 1

The correct option is B

The pitch of the sound keeps increasing as the length of the vibrating air column keeps decreasing

The frequency of a vibrating air column is inversely proportional to the length of the air column. As the bottle is filled up, the length of the air column keeps decreasing & hence frequency of the vibrating air column keeps increasing. Thus the sound produced will keep becoming shriller (high pitched) as the bottle is filled.