An open pipe is in resonance in 2nd harmonic with frequency f_1. Now one end of the tube is closed and frequency is increased to f_2 such that the resonance again occurs in nth harmonic. Choose the correct option.

An open pipe is in resonance in 2nd harmonic with frequency f_1. Now o

1.	An open pipe is in resonance in 2nd harmonic with frequency f_1. Now one end of the tube is closed and frequency is increased to f_2 such that the resonance again occurs in nth harmonic. Choose the correct option.
Answer» `n= 3f_(2)=(5)/(4)f_(1)` `n=5, f_(2)=(5)/(4) f_(1)` `n=3, f_(2)=(3)/(4)f_(1)` `n=5, f_(2)=(3)/(4)f_(1)` Solution :In case of open PIPE, frequency of second harmonics is, `f_(1)=(v)/(lambda)=(v)/(L) "" [ lambda=L]` In case of closed, pipe, frequency of `n^(TH)` harmonic, `f_(2)=(mv)/(4L)` where n is odd number. clearly `f_(2)=(n)/(4)f_(1)` If `n=3, f_(2) lt f_(1)` which is not acceptable In `n=5, f_(2)=(5)/(4)f_(1)` which is acceptable