Wave Machine

Materials

For this activity, you will need:

• Wooden skewers
• Jelly beans, gummy bears or similar soft lollies. You could also use playdough or blue tack if you don't want to use lollies.
• 2 pieces of wide sticky tape, each approximately 2 metres long
• A flat workspace

How to make a wave machine

Step 1: Assemble the wave machine

1. Cut two pieces of wide sticky tape, each approximately 2 metres long.
2. Lay one piece of tape on a flat surface with the sticky side facing up.
3. Place the wooden skewers across the tape so they are equally spaced and positioned at right angles to the tape.
4. Carefully place the second piece of tape over the top with the sticky side facing down.
5. Press the two tape strips together firmly to secure the wave machine.
6. Push a jelly bean onto the end of each skewer.
7. Stick one end of the wave machine to a chair or bookcase.

Step 2: Create a wave

1. Hold the other end of the wave machine.
2. Push one side of the skewer at the end of the tape up and down.
3. Watch how the movement travels through the machine.
4. Observe what happens when the wave reaches the opposite end.

Step 3: Experiment with different waves

1. Try creating small waves and large waves by changing how quickly you move the end skewer.
2. Observe how the wave changes as it travels along the machine.

Step 4: Investigate the effect of mass

1. Remove some of the jelly beans from the machine.
2. Create another wave.
3. Compare how the wave behaves with fewer jelly beans attached.
4. Record your observations.

How does it work?

A wave is a disturbance that transfers energy from one place to another.

When you move the first skewer:

• Energy is transferred to the next skewer.
• That skewer transfers energy to the next one.
• The disturbance travels through the machine as a wave.
• The energy moves along the machine, even though the individual skewers move only a short distance.

This model demonstrates a type of transverse wave, where the movement of the material is perpendicular to the direction the wave travels.

Many familiar waves behave in similar ways, including:

• Light waves
• Water waves
• Waves travelling along a rope
• Some seismic waves produced by earthquakes

The jelly beans add mass to the system. Changing the amount of mass can affect how the wave moves, allowing you to investigate how the properties of a medium influence wave behaviour.

Science fair project: Take it further

Once you have built your wave machine, investigate how different variables affect wave motion.

• Remove different numbers of jelly beans and compare the resulting waves. How does mass affect the movement of the wave?
• Change the size of the wave by moving the end skewer a greater or smaller distance. How does amplitude affect the wave?
• Create waves at different speeds. How does the frequency of the wave change the motion you observe?
• Build a longer or shorter wave machine. Does the length of the machine affect how the wave travels?
• Create a table to record your observations. Which design produced the largest wave? Which variables had the greatest effect on wave motion?