PASCO WA-9612 RESONANCE TUBE - Manual (Page 25)

21
012-03541E Resonance Tube
Experiment 3: Tube Length and Resonant Modes
Notes on Analysis
The successive piston positions correspond to
pressure antinode (displacement node) positions.
The spacing between these positions is equal to half
the wavelength of the sound.
Note
It is possible to measure the speed of sound in the
tube very accurately by a variation of this method.
Plot the length of the tube as a function of n, where
n is the number of antinodes in the standing wave
pattern (The graph shown is for the tube with both
ends closed.) The slope of this line will be equal to
λ
/2, and from this you can find the velocity.
5
5
5
5
5
5
5
0
10
20
30
40
50
60
70
80
0 1 2 3 4 5 6 7
Length (cm)
n
f(x) = 1.142500E+1*x + 2.857143E-2
R^2 = 9.999954E-1
1.5 kHz
v = 342.75 m/s
Compare with the theoretical value of
331.5 + 0.607 T = 342.42 m/s. (T = 18°C)
The intercept is related to the “effective length” of
the tube, and will change with frequency.