A tuning fork produces 5 beats/sec with a senometer wire of length 78 cm. if the length of the wire is increased by 2 cm, then there is a resonance between the tuning form and the wire. The frequency of the fork is

Options

A. 195 Hz
B. 190 Hz
C. 200 Hz
D. 180 Hz

Answer

A

Explanation

As, we know the for a sonometer wire nl=constant
`therefore(n_(1))/(n_(2))=(l_(2))/(l_(1))=(80)/(78)=(40)/(39) and n_(1) gt n_(2)`
`therefore` If N is the frequency of the tuning fork, then
`n_(1)=N+5 and n_(2)=N`
`therefore(N+5)/(N)=(40)/(39)`
`therefore40N=39N+195`
`thereforeN=195Hz`