Question

Two open pipes of length L are vibrated simultaneously. If length of one of the pipes is reduced by y. then the number of beats heats per second will be if the velocity of sound is v and `y lt lt L` :-
A. `(vy)/(2L^(2))`
B. `(vy)/(L^(2))`
C. `(vy)/(2L)`
D. `(2L^(2))/(vy)`

Answer 1

Correct Answer - A
`lamda_(1)=2L,lamda_(2)=2(L-y)`
`Delta f=f_(2)-f_(1)=(v)/(lamda_(2))-(v)/(lamda_(1))=(v)/(2)[(1)/(L-y)-(1)/(L)]`
`rArr (vy)/(2(L-y)L)=(vy)/(2L^(2))`