AP EAPCET 08-Jul-2022 Shift 1 Paper

In a closed organ pipe, only odd harmonics are present.
⇒ f1:f2:f3........=1:3:5
Where, f1=

v

4l′

v= speed of sound
and l= length of pipe.
In an open organ pipe, both odd and even harmonics are present.
⇒ f1:f2:f3.......=1:2:3.......
Also f1=

v

2l

In given question length of open pipe, l1=80‌cm
and (f2)open‌pipe=(f1)closed‌pipe
(2×f1)open‌pipe=(f1)closed‌pipe
⇒ 2×

v

2l1

=

v

4l2

So, length of closed pipe,
⇒ l2=

l1

4

=

80

4

=20cm