A tuning fork of known frequency 256 Hz makes 5 beats per second with the vibrating string of a piano . The beat frequency decreases to 2 beats/s when the tension in the piano string is slightly increased. The frequency of the piano string before increasing the tension was :

Options

A. (256 + 2) Hz
B. (256 - 5) Hz
C. (256 - 2) Hz
D. (256 + 5) Hz

Answer

B

Explanation

Unknown frequencyof string `v_(2) = v_(1) pm b = 256 pm 5 ` .
`v_(2) = 261` or 251 Hz.
when tension in string increases i.e., `V_(2)` increases then beat frequency decreases `therefore v_(2) = 251` Hz. So correct choice is (b) .