Describing Wave Motion (Edexcel GCSE Physics)

Describing Wave Motion

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

  • Amplitude

  • Wavelength

  • Frequency

  • Time Period

  • Wave velocity

  • Wavefront

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 (or sometimes just 'period') of a wave is defined as:

  The time taken for a single wave to pass a point

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

Wave Velocity

• Wave velocity (or wave speed) is defined as:

  The distance travelled by a wave each second

Wavefront

• Wavefronts are a useful way of picturing waves from above: each wavefront is used to represent a single wave

• The image below illustrates how wavefronts are visualised:

  • The arrow shows the direction the wave is moving and is sometimes called a ray

  • The space between each wavefront represents the wavelength

  • When the wavefronts are close together, this represents a wave with a short wavelength

  • When the wavefronts are far apart, this represents a wave with a long wavelength

Diagram showing a wave moving to the right, drawn as a series of wavefronts