Q 11-14-141JEE MainJEE Main 2025 (4 Apr, Shift 1)Easy
In an experiment with a closed organ pipe, it is filled with water up to $\left(\dfrac15\right)$th of its volume. The frequency of the fundamental note will change by:
Answer: (A) $25\%$
The air column (closed at the water surface) shrinks from $l$ to $\tfrac45l$. For a closed pipe $f = \dfrac{v}{4l}$, so
$$\frac{f_2}{f_1} = \frac{l}{4l/5} = \frac54$$
The frequency increases by $25\%$.
Solution by Sreeraj P, M.Sc Physics