Question

The first overtone frequency of an open organ pipe is equal to the fundamental frequency of a closed organ pipe. If the length of the closed organ pipe is 20 cm. The length of the open organ pipe is ______ cm.

Answer 1

$2 \times \frac {v}{2L_0} = \frac {V}{4L_C}$
$⇒ L_0 = 4L_C$
$⇒ L_0 = 4 × 20$
$⇒ L_0 = 80\ cm$

So, the answer is $80 \ cm$.