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Q. A cylindrical tube closed at one end contains air. It produces the fundamental note of frequency $512\, Hz$. If the tube is opened at both ends, the fundamental frequency that can be excited is

ManipalManipal 2010Electromagnetic Waves

Solution:

Let $l$ be the length of pipe, $v$ the speed of sound, then the fundamental tone or first harmonic of closed tube
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$n_{1}=\frac{v}{4 l}$
For open tube
$n_{2}=\frac{v}{2 l} $
$\therefore n_{2}=2 n_{1} $
Given, $ n_{1}=512 \,Hz $
$\therefore n_{2}=2 \times 512=1024 \,Hz$