Physics Waves PMDC 2020
PMDC Verified Question 99 of 125
Infrasonic wave has frequency
A
Less than 20Hz
B
Greater than 20Hz
C
20Hz
D
Greater than 20 kHz
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: Less than 20Hz
Concept:

The human auditory system can only detect sound waves within a specific frequency spectrum (20 Hz to 20,000 Hz).

Solution:

  • Sound waves with frequencies strictly less than 20 Hz are below the threshold of human hearing.


  • These low-frequency mechanical waves are scientifically termed "infrasonic" (infra = below).


  • Animals like elephants and whales utilize infrasonic waves for long-distance communication.


Why other options are incorrect:

Option D (Greater than 20 kHz) defines ultrasonic waves. Options B and C describe the normal audible range.

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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