Question 3 — If 20 compressions pass a - Questions at the end of the chapter - Chapter 10 - Sound Waves: Characteristics and Application (Exploration

Last updated at July 20, 2026 by

Question 3
If 20 compressions pass a point in 4 seconds, the frequency is (i) 80 Hz (ii) 5 Hz (iii) 10 Hz (iv) 0.2 Hz
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Answer: (ii) 5 Hz

  • Frequency = compressions time = 20 4 =5 Hz .
Option
Verdict & why (ν= 20 4 )
(i) 80 Hz
Wrong — that is 20× 4 , not 20÷ 4 .
(ii) 5 Hz
Correct — ν= 20 4 =5 oscillations per second.
(iii) 10 Hz
Wrong — that would need 40 compressions in 4 seconds.
(iv) 0.2 Hz
Wrong — that is 4÷ 20 , the time period, not the frequency.
Back to: 10.6.1 Wavelength, frequency and time period
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