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Free Organ Pipes MCQs with Answers

20 Organ Pipes MCQs from Physics, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.

Organ pipes produce standing sound waves in air columns, with resonance determined by whether each end is open or closed. The topic covers nodes, antinodes, fundamental frequency, harmonics, wavelength and end correction. Open pipes support all harmonics, while closed pipes support only odd harmonics under the ideal model.

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20 questions

1. In a pipe closed at one end, the fundamental note has

  • A. a node at the closed end and an antinode at the open end
  • B. antinodes at both ends
  • C. nodes at both ends
  • D. an antinode at the closed end

Explanation: The air cannot move at a closed end, so a node forms there, while the open end is free to vibrate and carries an antinode.

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Correct answer: a node at the closed end and an antinode at the open end

2. A closed organ pipe produces

  • A. all harmonics
  • B. only even harmonics
  • C. only odd harmonics
  • D. no harmonics at all

Explanation: The node and antinode boundary conditions can only be satisfied by odd multiples of the fundamental, so a closed pipe gives the first…

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Correct answer: only odd harmonics

3. Fundamental frequency of stationary waves in open pipe is ______________ times the frequency in closed pipe?

  • A. One
  • B. Two
  • C. Four time
  • D. None of these

Explanation: For pipes of the same length, the fundamental wavelength of an open pipe is 2L, while that of a closed pipe is 4L.

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Correct answer: Two

4. In open organ pipe___________________?

  • A. only even harmonics are present
  • B. only odd harmonics are present
  • C. both even and odd harmonics are present
  • D. selected harmonics are present

Explanation: An open pipe has displacement antinodes at both ends, allowing standing waves with wavelengths 2L/n for n = 1, 2, 3 and so on.

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Correct answer: both even and odd harmonics are present

5. On loading the prong of a tuning form with wax its frequency____________________?

  • A. increases
  • B. decreases
  • C. remains unchanged
  • D. may increase or decrease

Explanation: Adding wax to a tuning-fork prong increases its effective mass while its stiffness is nearly unchanged.

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Correct answer: decreases

6. Which one is the correct relation for fundamental frequency of open and closed pipe ?

  • A. fopen = 2 fclosed
  • B. fclosed = 2fopen
  • C. fopen = fclosed
  • D. fopen = 1 / f closed

Explanation: For pipes of the same length, the fundamental wavelength of an open pipe is 2L, while that of a closed pipe is 4L.

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Correct answer: fopen = 2 fclosed

7. The ratio of the fundamental frequency of an open end pipe to a pipe whose one end is closed is:

  • A. 1: 1
  • B. 1:2
  • C. 2:1
  • D. 1:4

Explanation: (A) Option 1: 1:1 ratio. This option states that the fundamental frequency of an open-end pipe is in a 1:1 ratio with a pipe whose one end…

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Correct answer: 2:1

8. A cylindrical resonance tube, opened at both ends, has a fundamental frequency 'f' in the air asshown in figure I. As shown in figure II, if half of the length of the resonance tube is dipped vertically into water,then the fundamental frequency in the air will be

  • A. f / 2
  • B. f
  • C. 2f
  • D. 4f

Explanation: The fundamental frequency of a cylindrical resonance tube opened at both ends is determined by the length of the air column.

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Correct answer: f / 2

9. A cylindrical resonance tube, opened at both ends, has a fundamental frequency 'f' in air as shown in the given figure I.As shown in figure II, if half of the length is dipped vertically into water, then the fundamental frequency of the air column will become

  • A. f/2
  • B. f
  • C. 3f/2
  • D. 2f

Explanation: When a cylindrical resonance tube is opened at both ends, the fundamental frequency of the air column is directly proportional to the…

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Correct answer: 2f

10. A pipe has a length of 1m. determine the frequencies of the fundamental and the first two harmonic if the pipe is opened at both end.(speed of sound in air is =340m/s)

  • A. 170hz, 340hz, 510hz
  • B. 120hz, 220hz, 390hz
  • C. 90hz, 230hz, 440hz
  • D. 210hz, 410hz, 510hz

Explanation: The frequencies of the fundamental and the first two harmonics for a pipe open at both ends are 170 Hz, 340 Hz, and 510 Hz, respectively…

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Correct answer: 170hz, 340hz, 510hz

11. A stationary wave is formed in a pipe which is open at both ends. If length of pipe is 10 cm, then what is the maximum possible wavelength of the wave?

  • A. 20 cm
  • B. 5 cm
  • C. 10 cm
  • D. 30 cm

Explanation: A pipe whose end opposite to the blowing end is open is called an open organ pipe.

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Correct answer: 20 cm

12. A first harmonic stationary sound wave is produced in the air of the cylinder, which is half filled with water. More water is added to the cylinder and now the first harmonic stationary wave is produced with a different frequency. What is the change in frequency and nature of displacement in the air at the surface of the water?

  • A. Nature of displacement = antinode change in frequency = decrease
  • B. Nature of displacement = antinode change in frequency = increase
  • C. Nature of displacement = node change in frequency = increase
  • D. Nature of displacement = node change in frequency = decrease

Explanation: Since the cylinder is half filled with water, we can treat this as a pipe where it is closed on one end and open on the other.

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Correct answer: Nature of displacement = node change in frequency = increase

13. A stationary wave is formed in a pipe which is open at one end. If length of pipe is L, then what is the maximum possible wavelength of the wave.?

  • A. L
  • B. 2L
  • C. 3L
  • D. 4L

Explanation: In a tube with two open ends f1 = v/2L, λ = v/f = 2L.In a tube with one open end and one closed end f1 = v/4L, λ = v/f = 4L.

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Correct answer: 4L

14. A stationary wave is formed in a pipe which is open at one end. If length of pipe is L, then what is the maximum possible wavelength of the wave?

  • A. L2
  • B. 2 L
  • C. 3 L
  • D. 4 L

Explanation: In a tube with one open end and one closed end f1 = v/4L, λ = v/f = 4L

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Correct answer: 4 L

15. A stationary wave is set up in a pipe of length L. If the pipe is open at one end and closed at other, what is the ratio of the fifth harmonic frequency to the first harmonic frequency?

  • A. 4
  • B. 6
  • C. 1/5
  • D. 5

Explanation: The frequency of the nth harmonic of a stationary wave in a pipe of length L open at one end and closed at the other is given by: fn =…

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Correct answer: 5

16. A 2m long pipe is open at both ends. What is its harmonic frequency?

  • A. 42.5 Hz
  • B. 85 Hz
  • C. 220 Hz
  • D. None of these

Explanation: The speed of the sound is = 340m/sIn an open pipe , the length of the pipe contains half a wavelength which means L= λ/2.Using the…

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Correct answer: 85 Hz

17. An organ pipe closed at one end has a length of 25 cm. Wavelength of the fundamental note is:

  • A. 25 cm
  • B. 50 cm
  • C. 100 cm
  • D. 75 cm

Explanation: The fundamental wavelength for an organ pipe closed at one end is given by the formula λ = 4L/n, where L is the length of the pipe and n…

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Correct answer: 100 cm

18. In open organ pipe of length l is the wavelength of the fundamental note is:

  • A. Equal to 1
  • B. Equal to 2L
  • C. Equal to 4L
  • D. Equal to 3l/2

Explanation: Equal to 2L: This option is correct. In an open organ pipe, the fundamental wavelength corresponds to the length of the pipe, so the…

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Correct answer: Equal to 2L

19. An organ pipe is open at both ends at its fundamental frequency. Neglecting any end effects, what wavelength is formed by this pipe in this mode of vibration, if the pipe is two meter long?

  • A. 2m
  • B. 4m
  • C. 6m
  • D. 8m

Explanation: For an open pipe at both ends, the fundamental frequency is given by: f = v/2LWhere v is the speed of sound and L is the length of the…

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Correct answer: 4m

20. An organ pipe of length T has one end closed but the other end open. What is the wavelength of the fundamental node emitted?

  • A. 4 × T
  • B. 2 × T
  • C. 3 × T
  • D. 1 × T

Explanation: The fundamental mode of a closed-open organ pipe produces a wavelength that is four times the length of the pipe.

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Correct answer: 4 × T
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