Question

Two tuning forks `n_1 " and "n_2` when sounded together produces 5 beats per second . If the fork `n_1` is in resonance with a closed tube of length 8cm and other `n_2` is resonance with an open tube of length 16.5cm the frequency `n_1` will be
A. 165Hz
B. 140Hz
C. 140Hz
D. 145Hz

Answer 1

Correct Answer - A
`n_1-n_2 = 5`
`(v)/(4l_1) - (v)/(2l_2) =5`
`v[1/32-1/33]=5`
`v[33-32]=5xx32xx33`
`v=32xx33xx5`
`n_1 = (v)/(4l_1) = (32xx33xx5)/(4xx8) = 165Hz`