PASCO WA-9612 RESONANCE TUBE - Manual (Page 10)

Resonance Tube 012-03541E
6
The formulas and diagrams shown above for reso-
nance in a tube are only approximate, mainly because
the behavior of the waves at the ends of the tube
(especially at an open end) depends partially on
factors such as the diameter of the tube and the
frequency of the waves. The ends of the tubes are not
exact nodes and antinodes. It can be a useful experi-
ment to investigate the wave behavior at the ends of
the tube using the microphone. The following empiri-
cal formulas give a somewhat more accurate descrip-
tion of the resonance requirements for standing waves
in a tube.
For an open tube:
L + 0.8d = nl/2, n = 1, 2, 3, 4,….
where L is the length of the tube and d is the diameter.
For a closed tube:
L + 0.4d = nl/4, n = 1, 3, 5, 7, 9,….
where L is the length of the tube and d is the diameter.
➤ NOTE: When using the microphone to
investigate the waveform within the tube, be
aware that the microphone is a pressure trans-
ducer. A maximum signal, therefore, indicates a
pressure antinode (a displacement node) and a
minimum signal indicates a pressure node
(displacement antinode).
➤ NOTE: The following four experiments require the WA-9612 Resonance Tube,
and a function generator capable of driving the 32
Ω
, 0.1 W speaker (such as the
PASCO PI-9587C Digital Function Generator). You will also need banana plug
hook-up wires to connect the function generator to the speaker.
An oscilloscope (such as the PASCO SB-9591 Student Oscilloscope) is recom-
mended for all the experiments and required for Experiment 4.
If you are using a function generator that does not provide an accurate indication of
frequency output, you will need a frequency counter (such as the SB-9599A
Universal Digital Meter) for all four experiments.