•• Working for a small gold mining company, you stumble across an(adsbygoogle = window.adsbygoogle || []).push({});

abandoned mine shaft that, because of decaying wood shoring, looks too

dangerous to explore in person. To measure its depth, you employ an audio

oscillator of variable frequency. You determine that successive resonances are

produced at frequencies of 63.58 and 89.25 Hz. Estimate the depth of the shaft.

I pictured the mine or cave as a one open end pipe or string tied at one end. To estimate the depth I only need to find L.

In other words:

maximum Lambda or Lambda(sub1)=4L

Lambda-sub1= velocity of sound/fundamental frequency=13.36969m.

Fundamental frequency is equal to the subtraction of the consecutive frequencies given.

Then,

(maximum Lambda/4)=L

should be equal to the maximum depth of the mine. My answer is 3.34m

Why is this answer wrong?

Thank you.

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# Standing waves and variable frequency

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