PASCO WA-9857, Инструкция по эксплуатации

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String Vibrator String Density and Wavelength
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4. Loosen the clamp on the String Vibrator and slide it along the table to adjust the length of the
vibrating part of the inelastic cord. Adjust it so that knot connecting the elastic and inelastic
cords is at a node. (The amplitude may be low, but it will increase after the next steps.)
5. Observe the elastic cord. You want a node to occur at the point where the cord is attached to
the vibrating blade, but that will probably not be the case initially. If you are using the fixed-
frequency power supply continue to the next step. If you are using the Sine Wave Generator,
skip to the optional setup section.
6. With a felt-tip pen, mark the elastic cord at the node closest to the blade.
7. Disconnect the power. Adjust the elastic cord so that it is attached to the blade at the point that
you marked. Restore the power connection.
8. Adjust the position of the String Vibrator again so that the knot connecting the elastic and
inelastic cords is at a node. Confirm that the connection to the blade is also at a node.
Optional Setup for Variable-frequency Sine Wave Generator
First follow steps 1–5. After you have positioned the String Vibrator so that a node occurs at the
knot, adjust the driving frequency so that another node occurs at the blade. As you adjust the
frequency, adjust the position of the String Vibrator so that the knot stays at a node.
Demonstration
The picture above shows the demonstration using the constant-frequency AC power supply. You
can see that the cord with the higher linear density (the elastic cord) has a smaller wavelength.
Since both have the same frequency, the denser cord must have a lower wave speed.
Further Demonstration
Compare the wavelengths of two parallel strings. Tie both strings to the same String Vibrator, but
run them out to separate pulleys. Apply the same tension to both strings, but adjust the lengths
separately (by moving the pulleys along the edge of the table) to achieve standing waves of
different wavelengths.