Q82 / 90 · JEE Main 2024 (06 Apr Shift 2) · Physics
Two open organ pipes of lengths $60 \mathrm{~cm}$ and $90 \mathrm{~cm}$ resonate at $6^{\text {th }}$ and $5^{\text {th }}$ harmonics respectively. The difference of frequencies for the given modes is _______ $\mathrm{Hz}$. (Velocity of sound in air $=333 \mathrm{~m} / \mathrm{s}$ )
Correct answer: 740
Solution
The difference in frequency in open organ pipe $=$
$\begin{aligned}
& \mathrm{f}=\frac{\mathrm{nv}}{2 \mathrm{~L}} \\
& \Delta \mathrm{f}=\frac{6 \mathrm{v}}{2 \times 0.6}-\frac{5 \mathrm{v}}{2 \times 0.9} \\
& \mathrm{v}=333 \mathrm{~m} / \mathrm{s} \\
& \Delta \mathrm{f}=740 \mathrm{~Hz}
\end{aligned}$
Hence, the correct answer is 740.