Question:medium

A pipe of length 80 cm is open at both ends. A second pipe, closed at one end, has the same fundamental frequency as the open pipe. The length of the second pipe is:

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Open pipe fundamental: \(v/2L\), closed pipe fundamental: \(v/4L\).
Updated On: Jun 19, 2026
  • 80 cm
  • 160 cm
  • 40 cm
  • 120 cm
Show Solution

The Correct Option is C

Solution and Explanation

Step 1: Open pipe fundamental.
f₁ = v/(2L₁); with L₁ = 80 cm, f₁ = v/160.

Step 2: Closed pipe fundamental.

f₂ = v/(4L₂).

Step 3: Equating frequencies.

v/160 = v/(4L₂).

Step 4: Solving for L₂.

4L₂ = 160 → L₂ = 40 cm.

Step 5: Physical note.

A closed pipe's fundamental is half that of an open pipe of the same acoustic length scale.

Step 6: Conclusion.

The required closed pipe length is 40 cm.
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