Tuning Fork

1. May 8, 2005

Haftred

A vibrating tuning fork is held above a column of air [...] The shortest length of an air column that produces resonance is L(1) - 0.25 m. The next length that produces resonsnace is L(2) - 0.80 m. 343 m/s is what I will use for sound. How can I find the original frequency of the tuning fork?

The original problem can be found here: (Number 3)

2. May 8, 2005

OlderDan

Your minus signs are supposed to be equal signs. An explanation with some pictures worth a thousand words can be found here.

http://hyperphysics.phy-astr.gsu.edu/hbase/waves/clocol.html#c1

If you click on the "Resonance tube experiment" you can even put in your numbers to explore the solution for the ideal case. The problem as stated seems to be throwing you a curve. If the first length of air is 0.25m, the second length of air should ideally be three times that, or 0.75m. Apparently they are expecting you to assume there is deviation from ideal behavior because of the diameter of the tube, and use the difference between 0.80m and 0.25 m to come up with the half-wavelength. There is in fact such an "effective length" effect, briefly described in this description of the experiment.

http://world.casio.com/edu/resources/program_lib/ea200/pdf/07_p26_27.pdf