Waves

The big idea is that waves travel, but the solid, liquid or gas that they travel though doesn't travel along with the wave. You can see this in action with a floating object on a pond. The waves travel from one side of the pond to the other, but the floating object does not travel along with it - it just moves up and down.

To show pupils this idea, use a large tray of water with a small floating object in it. Cause ripples by repeatedly tapping the surface of the water and watch the waves travel. Notice how the floating object doesn't shoot across the surface with the wave - it just bobs up and down.

It is even better if you can use a paddling pool or a pond (not a wildlife pond!) Dropping stoned into the water lets children observe waves on a larger scale.

The key problem with waves on a beach is that waves break along the seashore. In breaking waves, the water actually moves up and down the beach - this isn't helpful when thinking about waves in science.

Videos of Mexican waves in football stadium can be helpful to show that the wave moves, but the people just bob up and down.

Slinkys or long skipping ropes are also excellent for showing how waves travel without the actual spring or rope traveling with the wave.

Key questions

If you drop a stone into a pond, how do the waves move? (The waves are circular and spread outwards).
How does a floating object move as the wave travels past it? (It just bobs up and down).T
Does the floating object travel along with the wave? (No - it says in the same place).
If you drop a bigger stone in the water, how will this affect the wave? (It will have a bigger 'amplitude' (the height of the wave will be bigger), but it won't travel faster).

Common misconceptions

Waves transport matter. (Matter is only displaced from its rest position and returns

to that rest position once the wave has travelled through.)

Looking at the height of waves, smaller waves travel faster than larger waves.

(No, if the water depth remains the same, the speed of the water waves stays the

same.)

Waves do not have energy. (They do, as they are defined as a transfer of energy)

You need matter for a wave to travel in. (The light from the Sun is a wave and it

reaches us despite the vacuum of space.)

Progression

EYFS

Know that some objects can move in a repetitive way.

Pupils should see and be able to talk about waves and ripples on water. They will see waves on the beach and also when a stone is dropped into a pond.

KS1

Pupils should know that waves travel along the surface or water, but that a floating object will not travel along with the wave.

KS2

Pupils will be able to compare the waves on water with a slinky or a rope that is moved at one end.

The should be able to describe waves with small amplitudes and large ones.

They should know that sound is a wave in the air and should be able to compare water waves with sound waves.

KS3

Pupils should know that sound and light travel as waves. These waves can be reflected and refracted. They should understand and use the terms: amplitude, wavelength and frequency.