Introduction

To describe a wave, you need to know a few of its properties.

One property is its wavelength. For a sound wave, this corresponds to how high or how low a note sounds. For a light wave, it corresponds to the colour of light.

Another property is the amplitude, which corresponds to loudness for a sound wave or brightness for a light wave.

To describe a wave, you need to know a few of its properties.

One property is its wavelength. For a sound wave, this corresponds to how high or how low a note sounds. For a light wave, it corresponds to the colour of light.

Another property is the amplitude, which corresponds to loudness for a sound wave or brightness for a light wave.

The wavelength of a wave

One of the basic characteristics of a wave is its **wavelength**. This is the distance from one peak, or crest, to the next. This is the same as the distance from one dip, or trough, to the next.

All the arrows on Fig.1 indicate the

**wavelength**The Greek letter λ (lambda) is used for the wavelength of a wave.

This is how waves with the same wavelength would appear in a ripple tank:

The black lines shown in the diagram above are called wavefronts, and represent either all the crests or all the troughs in a wave.

The amplitude of a wave

The volume of sound, the

**energy****amplitude**of the wave. The arrows on the wave in Fig.3 below indicate the

**amplitude**The amount of energy in a wave is proportional to its amplitude. The larger the amplitude, the more energy it carries, and the more dangerous it can be. For example, low-energy sound is perfectly safe. However, prolonged exposure to high-intensity sounds can cause loss of hearing and even deafness.

You cannot really tell the amplitude of a wave in a ripple tank. If the amplitude is too large, the water may splash out of the tank!

Wave period and frequency

'Keep your radio tuned to 102.2 FM for all the latest and greatest hits.'
Have you ever wondered what the DJ means by 102.2? It is the

**frequency**With waves,

**frequency**is how many peaks go past in a given time, usually one second.

Look at the waves in Fig.4 above.

Divide the number of waves by the time you counted for. This will give you the frequency of the waves.

The unit of frequency is the hertz (Hz). One hertz is equal to one particular event per second. In this example, it is one wave per second. If you were counting buses, one hertz would mean one bus per second.

The period of a wave is the time between one crest and the next appearing (this is also true for troughs). Can you use the clock to time the period of the waves above?

It is easier to use the equation below, which relates the frequency f to the period

Click on the figure below to interact with the model.

We can work out the period of the light from its frequency.

The light flashes on and off with a frequency of 4 Hz. |

The period, T, of the flash is found by dividing 1 by the frequency. |

The period is equal to 1/4, or 0.25 seconds. |

Summary

A wave has a wavelength, an amplitude, a frequency, and a period.

The wavelength is the distance from one peak to the next, or from one trough to the next.

The amplitude is the maximum height of a wave from its rest position.

The frequency is the number of waves per second.

The period and the frequency are related by the equation:

A wave has a wavelength, an amplitude, a frequency, and a period.

The wavelength is the distance from one peak to the next, or from one trough to the next.

The amplitude is the maximum height of a wave from its rest position.

The frequency is the number of waves per second.

The period and the frequency are related by the equation:

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