The fundamental frequency in an open organ pipe is equal to the third harmonic of closed organ pipe. If the length of the closed organ pipe is 20 cm, the length of the open organ pipe is

Step-by-step solution

For closed organ pipe, third harmonic 3 v 4 l cop For open organ pipe, fundamental frequency v 2 l oop . According to question f o o p = 3 f c o p ⇒ v 2 l o o p = 3 v 4 l c o p l o o p = 2 3 × l c o p = 2 3 × 20 ≈ 13.2   c m