Q 11-14-002NEETNEET 2025Top questionEasy
A pipe open at both ends has a fundamental frequency $f$ in air. The pipe is now dipped vertically in a water drum to half of its length. The fundamental frequency of the air column is now equal to :
Answer: (B) $f$
Concept. Open pipe: $f = \dfrac{v}{2L}$. Dipping it in water closes the lower end and halves the air column, giving a closed pipe: $f' = \dfrac{v}{4L'}$.
Step 1. New air column. $L' = \dfrac{L}{2}$, closed at the water surface.
Step 2. New fundamental.
$$f' = \frac{v}{4(L/2)} = \frac{v}{2L} = f$$
Answer. $f$ (Option B).
Solution by Sreeraj P, M.Sc Physics