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Amplitude

As waves travel, they set up patterns of disturbance. The amplitude of a wave is its maximum disturbance from rest (its undisturbed position).

Wavelength

The wavelength (λ) of a wave is the distance between a point on one wave and the same point on the next wave. It is often easiest to measure this from the crest (top) of one wave to the crest of the next wave or the trough (bottom) of one wave to the trough of the next wave. It doesn't matter where you measure it, as long as it is the same point on each wave (look for where the pattern repeats).

You should also be able to count the number of waves in a diagram.

You should be able to see that this diagram includes three waves – the pattern repeats three times.

Frequency

The frequency of a wave is the number of cycles of a wave that occur in one second.

The unit of frequency is the hertz (Hz). 1 Hz is one wave per second. It is common for kilohertz (kHz), megahertz (MHz) and gigahertz (GHz) to be used when waves have very high frequencies.

Representing a transverse wave graphically

You need to know about two types of graph that can be used to represent transverse waves:

• displacement-distance graphs
• displacement-time graphs

Displacement-distance

A displacement-distance graph is a snapshot of the wave at any given time.

You should be able to work out the wavelength of a wave from a displacement-time graph.

Displacement-time

A displacement-time graph shows how the displacement of one point on the wave varies over time.

You should be able to work out the frequency of a wave from a displacement-time graph – remember the frequency is the number of waves per second.