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WAEC - Physics (2016 - No. 29)

The diagram given 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 notes
\(\frac{V}{L}\)
\(\frac{5VL}{2}\)
\(\frac{5L}{4V}\)
\(\frac{5V}{4L}\)

Explanation

L = \(\frac{5\lambda}{4}\)

\(\lambda = \frac{4L}{5}\)

But \(\lambda = f\lambda\)

f = \(\frac{v}{\lambda} = \frac{v}{\frac{4L}{5}}\)

= \(\frac{5v}{4L}\)

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