Q.

The 4th overtone of a closed organ pipe is same as that of 3rd overtone of an open pipe. The ratio of the length of the closed pipe to the length of the open pipe is     [2023]

1 8 : 9  
2 9 : 7  
3 9 : 8  
4 7 : 9  

Ans.

(3)

4th overtone of closed organ pipe =9υ0=9×ν4L               ...(i)

3rd overtone of open organ pipe =4υ0=4×ν2L'                  ...(ii)

As per question, 9υ0=4υ0

From equations (i) and (ii), 9×ν4L=4×ν2L'

LL'=98