Concepts

Transverse waves, travelling waves, standing waves, damping, impedance, reflection, transmission

Overview

The shive wave machine is a torsional oscillator consisting of many rods attached to a twisting wire. Many aspects of waves can be seen with it, including travelling waves, wave speed, and reflection/transmission at interfaces. There are three oscillator segments available: one with long rods, one with short rods, and one that tapers smoothly between long and short rods.

Details

Equipment

• [1] Long-arm wave machine segment
• [1] Short-arm wave machine segment
• [1] Tapering-arms wave machine segment
• [2] Coupling clamp
• [1] Damping attachment
• [1] Hard stop

Classroom Assembly

1. Fold up the bases on the desired wave machine segments so that they stand up.
2. Couple the bases together, if desired.
3. Add damping and/or a hard stop, if desired.

Important Notes

• Do not apply sharp large-amplitude oscillations! This damages the machine.

Script

In general, operation is straightforward: introduce gentle oscillations to the machine by hand, moving the end of a rod up and down. Instead of a script, here is a list of demonstrations to try:

• Travelling waves: single pulse excited by hand
  
• Standing waves: continuous wave excitation
• Wave speed: contrast a pulse through the short-arm segment and a pulse through the long-arm segment
• Damping: put the damping attachment on a rod and send in a travelling wave; damping can be adjusted by changing the position at which the attachment couples to the rod
• Reflection and phase shift: can put hard stop or not to illustrate the phase shift from reflections off of higher impedance media
• Reflection and refraction with impedance mismatch or discontinuity: attach short-arm and long-arm segments directly and send in a travelling wave; can be contrasted with short-arm and long-arm segments joined by the tapering-arms segment

Additional Resources