The third overtone of an open organ pipe of length lo has the same frequency as the third overtone of a closed pipe of length lc. The ratio lo /lc is equal to
(a) 2
(b) 3/2
(c) 5/3
(d) 8/7
Correct Answer is: (d) 8/7
Let no and nc be the fundamental frequencies of the open and closed pipes.
∴ no = V/2l and nc =V/4lc .
Third overtone of the closed pipe = 7nc.
Third overtone of the open pipe = 4no.
