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WAEC Physics 2016 Objective — Question 31

Question 31 of 50 from the West African Examinations Council (WAEC) Physics 2016 Objective paper, with the correct answer and a full explanation.

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The diagram above illustrates the waveform of a note produced by vibrations in an air column of length L. If the speed of sound in air is V, derive an expression for the frequency of the note.

Diagram for question 31
  • A. V/L
  • B. 5VL/2
  • C. 5L/4V
  • D. 5V/4LCorrect

Explanation

L=5λ/4 (from the waveform, the length equals 5/4 of a wavelength); v=fλ → f=v/λ=v/(4L/5)=5v/4L.

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