Two forks A and B when sounded together produce
four beats `s^(-1)`. The fork A is in unison with 30 cm
length of a sonometer wire and B is in unison with 25
cm length of the same wire at the same tension. The
frequencies of the forks are

Options

A. 24Hz, 28Hz,
B. 20Hz, 24Hz
C. 26Hz, 30Hz
D. 16Hz, 20Hz

Answer

B

Explanation

`n_2-n_1 =4`
`n_1l_1=n_2l_2`
`n_1=(n_2l_2)/(l_1)`
`n_2-(n_2l_2)/(l_1) = 4 therefore n_2 = ((l_1-l_2))/(l_1) = 4`
`n_2=(4xx30)/(5) = 24Hz " and " n_1=20Hz`