Describing Wave Motion (AQA GCSE Physics: Combined Science)

• When describing wave motion, there are several terms which are important to know, including:
  • Amplitude
  • Wavelength
  • Frequency
  • Period

Amplitude

• Amplitude is defined as:

The distance from the undisturbed position to the peak or trough of a wave

• It is given the symbol A and is measured in metres (m)
• Amplitude is the maximum or minimum displacement from the undisturbed position

Wavelength

• Wavelength is defined as

The distance from one point on the wave to the same point on the next wave.

• In a transverse wave:
  • The wavelength can be measured from one peak to the next peak

• In a longitudinal wave
  • The wavelength can be measured from the centre of one compression to the centre of the next

• The wavelength is given the symbol λ (lambda) and is measured in metres (m)
• The distance along a wave is typically put on the x-axis of a wave diagram

Diagram showing the amplitude and wavelength of a wave

Frequency

• Frequency is defined as:

The number of waves passing a point in a second

• Frequency is given the symbol f and is measured in Hertz (Hz)

Time Period

• The time period of a wave is defined as:

The time taken for a single wave to pass a point 

• This can also be stated as

  The time taken for one full cycle of a wave

• The time period is given the symbol T and is measured in seconds (s)

• On a graph, this can be seen by the time taken for a complete wavelength, if the horizontal axis is time

Diagram showing the time period of a wave