Physics Waves PMDC 2020
PMDC Verified Question 95 of 125
Ratio of fundamental frequency of Open Organ pipe to closed organ pipe is
A
1:2
B
2:1
C
1:4
D
4:1
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: 2:1
Concept:

The harmonic frequencies of organ pipes differ critically based on boundary conditions (open vs. closed ends).

Formula:

$$ f_{\text{open}} = \frac{v}{2L} $$
$$ f_{\text{closed}} = \frac{v}{4L} $$

Solution:

  • For a pipe open at both ends, the fundamental frequency is \( f_{\text{open}} = \frac{v}{2L} \).


  • For a pipe closed at one end, the fundamental frequency is \( f_{\text{closed}} = \frac{v}{4L} \).


  • Calculate the ratio: \( \frac{f_{\text{open}}}{f_{\text{closed}}} = \frac{v/2L}{v/4L} = \frac{4L}{2L} = \frac{2}{1} \).


  • The ratio is exactly 2:1.


Why other options are incorrect:

Option A (1:2) is the inverse ratio (closed to open). Options C and D result from mathematically confusing lengths or squaring values incorrectly.

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

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