Question

when a tuning fork vibrates over an open pipe and the air in the pipe starts to vibrate, the vibrations in the tube are caused by
a) beats.
b) reinforcement.
c) harmonics.
d) resonance.

Explanation:

• Beats are periodic amplitude variations from two slightly different frequencies, not the cause here.
• Reinforcement is a type of interference, not the specific mechanism for this air vibration.
• Harmonics are integer multiples of a fundamental frequency, not the cause of the pipe's air vibration.
• Resonance occurs when an external vibration matches an object's natural frequency, causing it to vibrate strongly. This is exactly what happens when the tuning fork makes the air in the open pipe vibrate.

Answer:

D) resonance.