Question

A tuning fork produces 5 beats `s^(-1)` with a sonometer
wire of length 78 cm. If the length of the wire
iscreased byy 2 cm, then there is a resonance between
the tuning fork and the wire. The frequency of the
fork is
A. 195 Hz
B. 190 Hz
C. 200 Hz
D. 180 Hz

Answer 1

Correct Answer - a
For the sonometer wire
`nl=` constant
`therefore n_(1)/n_(2)=l_(2)/l_(1)=80/78=40/36` and `n_(1) gt n_(2)`
If N is the frequency of the tuning fork, then
`n_(1)=N+5 and n_(2)=N`
`therefore (N+S)/N=40/39`
`40N=39N+195`
N=195 Hz