The frequency of a wave is equal to the reciprocal of its period:
[tex]f= \frac{1}{T} [/tex]
where f is the frequency and T the period.
The violin string of our problem emits a note with frequency f=440 Hz, so if we re-arrange the previous equation, we can find the period of the string's oscillation:
[tex]T= \frac{1}{f}= \frac{1}{440 Hz}=0.0023 s [/tex]
