A pipe open at both ends has a fundamental frequency f in air. The pipe is now dipped vertically in

Q: What is NEET?

NEET is a competitive examination conducted in India. This question is from the 2025 NEET Physics paper.

Q: How can I prepare for NEET Physics?

To prepare for NEET Physics, practice previous year questions (PYQs), understand concepts thoroughly, and solve mock tests regularly. This 2025 question covers Waves topic.

Q: What is the difficulty level of this question?

This NEET 2025 Physics question has a medium difficulty level and is marked as an important question and is one of the most repeated questions.

Q: Where can I find more NEET previous year questions?

You can find more NEET previous year questions on AspirantMitraa. Browse by subject, topic, year, and difficulty level to practice effectively.

Question

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:

Accepted Answer

Correct Answer: C — The frequency remains fStep-by-step Solution:Case 1 — Open pipe of length L:Both ends are antinodes. Fundamental mode: L = λ/2 → λ = 2LFundamental frequency: f = v/2L ...(i)Case 2 — Pipe dipped to half its length:When half the pipe is submerged in water, the water surface acts as a closed end (node). Effective air column = L/2. The pipe now behaves as a closed pipe.In a closed pipe: closed end is a node, open end is an antinode. Fundamental mode: L' = λ'/4λ' = 4L' = 4(L/2) = 2LNew fundamental frequency: f' = v/λ' = v/2L ...(ii)From (i) and (ii): f' = fPhysical insight: Two effects exactly cancel — halving the length doubles the frequency, but changing from open to closed pipe halves the frequency. Net result: no change.Why Option A (2f) is wrong: This would occur only if the length halved with no change in pipe type. The open→closed change compensates exactly.Why Option B (f/2) is wrong: This would require the wavelength to double, which is not what happens here.Why Option D (3f/2) is wrong: 3f/2 is not produced by any fundamental mode calculation here; it may be confused with overtones.Key Concepts from Waves (NCERT Class 11, Chapter 15):Open pipe: Both ends antinodes. ffundamental = v/2L. All harmonics present: f, 2f, 3f...Closed pipe: Closed end = node, open end = antinode. ffundamental = v/4L. Only odd harmonics present: f, 3f, 5f...Speed of sound in air at room temperature ≈ 346 m/s; v ∝ √T (in Kelvin).This problem elegantly shows that two separate effects can cancel each other perfectly.

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:

Master NEET with Our Test Series

More Questions from Waves

Frequently Asked Questions

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:

Master NEET with Our Test Series

More Questions from Waves

Frequently Asked Questions