Q.

The fundamental frequency of a closed organ pipe is equal to the first overtone frequency of an open organ pipe. If the length of the open pipe is 60 cm, the length of the closed pipe will be           [2024]

1 30 cm  
2 45 cm  
3 60 cm  
4 15 cm  

Ans.

(4)

λ4=L1                 2(λ2)=λ=L2

f1=v4L1             f2=vL2

f1=f2

v4L1=vL2L2=4L1

60=4×L1L1=15 cm