Physics Waves SZABMU 2023
PMDC Verified Question 35 of 125
Which of the following factors does not affect the speed of sound in air?
A
Density of gas
B
Moisture in air
C
Temperature
D
Pressure of gas
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option D: Pressure of gas
Concept:

Sound velocity depends on the elastic and inertial properties of the gas.

Formula:

$$ v = \sqrt{\frac{\gamma P}{\rho}} $$

Solution:

  • According to Boyle's law, at a constant temperature, any increase in gas pressure (\( P \)) results in an exactly proportional increase in its density (\( \rho \)).


  • Because both variables increase by the same factor, the ratio \( P/\rho \) remains perfectly constant.


  • Therefore, changing the pressure has absolutely no effect on the speed of sound.


Why other options are incorrect:

Temperature dramatically alters speed. Moisture (humidity) lowers the average molecular mass of air, decreasing density and thus increasing sound speed.

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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