Q. Two organ pipes both closed at one end have length l and$(l + \Delta l)$. Neglect ed correction. If velocity of sound I air is v , the number of beats $s^{- 1}$ is
A) $v/4l$
B) $v/2l$
C) $\frac{v}{4l^{2}}(\Delta l)$
D) $\frac{v}{2l^{2}}(\Delta l)$
Explanation
(c) Number of beats $s^{- 1} = n_{1} - n_{2} = \frac{v}{3l} - \frac{v}{4(l + \mathrm{\Delta}l)}$
$= \frac{v}{l}\left\lbrack \frac{l + \mathrm{\Delta}l - l}{l(l + \mathrm{\Delta}l)} \right\rbrack = \frac{v\mathrm{\Delta}l}{4l^{2}}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.