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 ccm
C. 120 cm
D. 140 cm

Answer

c

Explanation

The fundamental frequencies of closed organ pipe
are given as, `v_(c)=v/(4l)`
`because` Second overtone of an open organ pipe `v_(2)=(3v)/(2l_(1))`
Where `l_(1)=` length of the open pipe
`because v_(c)=v_(2)`
`rArr v/(4l)=(3v)/(2l_(1))rArr l_(1)=6l=6xx20`
`therefore l_(1) = 120` cm