Waves transport energy from one place to another. They are temporary displacement in either matter or fields. There are two types of wave, those like sound which are called and the more common .

In waves the displacement is at right angles with the direction that the wave is travelling. While in waves the displacement is along the direction that the wave is travelling.

The maximum displacement is known as the of a wave and is measured from the , this is where the matter (or field) would be if there wasn't a disturbance.

We can also measure the , this is simply the distance between two identical parts of the wave. For ease we normally measure peak to peak or trough to trough.

There are two related time measurements we can make. The is the amount of time to complete one cycle (wave) and is the number of cycles (waves) in a bit of time. One cycle per second is one hertz.

A high frequency sound wave has a high and a sound wave with a large amplitude sounds .

If a wave has a wavelength, λ and a frequency, f, then the wave speed, c, can be calculated by:

	c = λ f
where: c = Wave speed in , λ = Wavelength in , f = Frequency in ,

Complete the table below (to 1 s.f.):

Wave	Frequency	Wavelength	Speed
Yellow light	0.51 x 10 15 Hz	590 x 10 -9 m
X - rays		0.1 x 10 -9 m
Microwave	6 x 10 9 Hz
Radio waves from space		0.8 m

Wave speeds are generally fixed by the medium the wave is travelling through. All electromagnetic waves (light) travel at the same speed in a . So as their wavelength increases their frequency decreases in a 'see-saw' relationship.