Physics Waves MDCAT 2010
PMDC Verified Question 119 of 125
An organ pipe closed at one end has a length of 25 cm. Wavelength of the fundamental note is
A
25 cm
B
100 cm
C
50 cm
D
75 cm
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: 100 cm
Concept:

For a pipe closed at one end, a stationary wave forms with a node at the closed boundary and an antinode at the open boundary.

Formula:

$$ L = \frac{\lambda_1}{4} $$

Solution:

  • The fundamental mode (first harmonic) has the simplest pattern: one node and one antinode, spanning one-quarter of a wavelength.


  • Rearranging the formula gives \( \lambda_1 = 4L \).


  • Substitute the given length: \( \lambda_1 = 4 \times 25 \text{ cm} = 100 \text{ cm} \).


Why other options are incorrect:

A student might incorrectly use the formula for an open pipe (\( \lambda = 2L \)) resulting in 50 cm, or equate wavelength directly to length (25 cm).

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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