A stretched sonometer wire is in unison with a tuning fork. When length of wire is increase by 1%, the number of beats heard per second is 5. then, the frequency of the fork is

Options

A. 500 Hz
B. 505 Hz
C. 255 Hz
D. 250 Hz

Answer

B

Explanation

`l_2 = (1.01)l_1`
`n_1-n_2 = 5 therefore nl_1 = n_2l_2`
`therefore n_1/n_2 = l_2/l_1 = 1.01`
`therefore n_1=1.01n_2`
`therefore 1.01n_2-n_2 = 5 therefore n_2xx0.01=5`
`n_2=500`
`therefore n_1=n_2+5=505Hz`