Final answer:
Resonance is the correct answer. It is a phenomenon that occurs when an object vibrates at its natural frequency or a multiple of that frequency.
Step-by-step explanation:
The correct answer to the question is Resonance.
Resonance is the phenomenon that occurs when an object vibrates at its natural frequency or a multiple of that frequency. In the case of a piano string, the frequency at which the string vibrates is determined by its length, tension, and mass per unit length. The frequency constant of proportionality, which determines the pitch of the sound produced by the string, is dependent on the resonant frequencies of the string.
For example, when the string of a particular length, tension, and mass per unit length vibrates at its fundamental frequency, the pitch produced is known as the first harmonic. If the string vibrates at twice the frequency of the fundamental frequency, it produces a pitch known as the second harmonic. These resonant frequencies, which are integer multiples of the fundamental frequency, determine the pitch of the sound produced by the piano string.