A tuning fork of frequency 256 Hz gives 5 beats `//`s with a vibrating string of a piano. The beat frequency decreases to 2, when tension in the string is slightly increased. What was the frequency of the piano string before increasing the tension ?

Explanation

Here, `n_(1)=256,m=5,n_(2)=?`
`n_(2)=n_(1)+-m=256+-5=261 or 251`
When tension in piano string is slightly increased, no. of beats `//` sec becomes 2.
`:. n_(2)=n_(1)+-m^(')=256+-2=258 or 254 Hz.`
`n_(2)` can be 251 Hz only, increasing to 254 Hz on increasing tension.