A string oscilating at foudamental frequency under a tension of 225 N produces 6 beats per second with a sonometer . If the tension is 256 N then again oscillating at fundamental note it produces beats per second with the same sonometer. What is the frequency of the sonometer ?

Options

A. 256
B. 225
C. 280
D. 186

Answer

D

Explanation

Let n. be the freq. of the string . As n. `prop sqrt(T)`.
If the freq. of sonometer = n , then
`(n - 6)/(n + 6) = sqrt((225)/(256)) = (15)/(16)`
16n - 96 = 15n + 90
n = 90 + 96 = 186
correct choice is (d).