Moderate

Which of the following set of frequencies can have constructive interference

Correct answer: A. 20Hz and 21Hz

  • A. 20Hz and 21Hz
  • B. 100Hz and 110Hz
  • C. 1000Hz and 2000Hz
  • D. None of the given options

Explanation

Option A (20Hz and 21Hz) is correct because these frequencies are very close, producing a low beat frequency of 1 Hz. This low frequency allows for observable constructive interference as the waves periodically reinforce each other. Option B (100Hz and 110Hz) produces a higher beat frequency of 10 Hz, making it harder to observe sustained constructive interference. Option C (1000Hz and 2000Hz) has an even higher beat frequency of 1000 Hz, which is too rapid for observable constructive interference. Option D is incorrect because Option A provides a valid set of frequencies for constructive interference.

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About Waves

Progressive waves transfer energy through oscillations, with wavelength, frequency, amplitude and wave speed related by v = fλ; sound speed depends on the medium. Superposition produces interference and stationary waves in strings and organ pipes, while simple harmonic motion describes the oscillation itself and must be distinguished from wave propagation.

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