O Levels Physics (5054)•5054/12/O/N/22
Explanation
Audible Range: 25 Hz to 20 kHz Steps:
- The audible frequency range for a healthy human ear is 25 Hz to 20 kHz.
- Frequencies below 25 Hz (infrasound) and above 20 kHz (ultrasound) are inaudible.
- Examine each option to identify the pair where both frequencies fall outside this range.
- Option B contains 20 Hz (below 25 Hz) and 25 kHz (above 20 kHz), satisfying the condition.
Why B is correct:
- 20 Hz is below the 25 Hz lower limit, and 25 kHz exceeds the 20 kHz upper limit, per the standard human hearing range definition.
Why the others are wrong:
- A: 500 Hz is within 25 Hz to 20 kHz.
- C: 25 Hz is at the lower limit (audible).
- D: 500 Hz is within 25 Hz to 20 kHz.
Final answer: B
Topic: Sound
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