The fundamental frequency of a closed organ pipe of length `20 cm` is equal to the second overtone of an organ pipe open at both the ends. The length of organ pipe open at both the ends is

Options

A. 80 cm
B. 100 cm
C. 120 cm
D. 140 cm

Answer

C

Explanation

The fundamental frequency for closed organ pipe is

`v = (upsilon)/(4L)` (L is length of closed organ pipe)
The second overtone of an open organ pipe has frequency `(3V)/(2L')`

Now, `(3 upsilon)/(2L') = (upsilon)/(4L)`
L' = 6L
`= 6 xx 20` cm
= 120 cm