Travelling Waves

A clear rubber rope filled with barium sulphate (a high density powder). It's about 9.5m long (~31 feet). One end is capped with a piece of acrylic rod, the other end is tied to a large brass lobster clasp.

This is a highly versatile demonstration. It can be used to demonstrate a number of concepts relating to waves and their propagation through media. It can be used to:

• Demonstrate how transverse waves can propagate through a string,

• Demonstrate the reflection of a pulse from a rigid-non-rigid boundary,

• Demonstrate reflection and transmission of waves at a boundary,

• Demonstrate standing waves,

• Demonstrate different modes of standing waves.

• 'Yak's milk'¹⁾ rope

The tubing is stretched across the lecture theatre with one end fixed to a hook on the wall while the other end is free to be manipulated by hand to show the various demonstrations. If no hook is available, attaching it to a door handle or a volunteer student may also work. For the non-rigid reflection and for the partial reflection and transmission at a boundary the far end is attached to a piece of cord and the other end manipulated.

The rope may also be laid flat on the floor and viewed with a camera from above. This is another way that travelling waves may be viewed. This definitely works better with the rope under tension and off the ground, though.

Finally, with a TA or volunteer, standing waves can be produced in the Yak's milk rope. Higher-order standing waves can be obtained with sufficiently great effort.