The figure below shows two standing waves for resonance of sound with fixed freq

Question

The figure below shows two standing waves for resonance of sound with fixed frequency. The first two consecutive lengths of air column in the tube are 25 cm. and 75 cm., respectively. If this experiment is performed in the room again at 68 degrees Fahrenheit, what would be the frequency corresponding to the sound resonances (unit of Hertz). Note: Lcorr is negligible.

Part B

The room is again at 68 degrees Fahrenheit. I adjust the water levels of my tube and find my first resonance at 30 cm, assuming I keep frequency constant which of the following other lengths would also be resonant?

Explanation / Answer

Given are the closed columns.

We know that, at a given tem, the speed of sound is:

v = 331.4 + 0.6Tc

T = 68 degF = 20 deg C

v = 331.4 + 0.6*20 = 343.4 m/s

we know that, for a closed cylinder,

f1 = v/4L

f1(1) = 343.4/4 x0.25 = 343.4 Hz

F12(2) = 343.4/4 x 0.75 = 114.47 Hz

Hence, F1(1) = 343.4 Hz and F1(2) = 228.93 Hz

B)None of these.

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