Q.

The second overtone of an open organ pipe has the same frequency as the first overtone of a closed pipe L metre long. The length of the open pipe will be       [2016]

1 L  
2 2L  
3 L2  
4 4L  

Ans.

(2)

Second overtone of an open organ pipe

          (Third harmonic) =3×υ0'=3×v2L'

First overtone of a closed organ pipe

          (Third harmonic) =3×υ0=3×v4L

According to question,

          3υ0'=3υ03×v2L'=3×v4L

    L'=2L