Question

A tuning fork of frequency 512 Hz makes 4 beats per second with tire vibrating string of a.piano. The beat frequency decreases to 2 beats per sec when the tension in the piano string is slightly increased. The frequency of the piano string before increasing the tension was

(a) 510 Hz

(b) 514 Hz

(c) 516 Hz

(d) 508 Hz

Answer 1

Correct option (d) 508 Hz

Explanation:

Let the frequencies of tuning fork and piano string be v₁ and v₂ respectively.

v₂ =v

Increase in the tension of a piano string increases its frequency.

If v₂ = 508 Hz, further increase in v₂ resulted in an  increase in the beat frequency. But this is not given in the question. 508 Hz. further increase in v₂ resulted in decrease in the beat frequency. This is given in the question" When the beat frequency decreases to 2 beats per second. Therefore, the frequency of the piano string before increasing the tension was 508 Hz.