Describing Wave Motion (Edexcel IGCSE Physics) : Revision Note

Describing wave motion

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

  • Amplitude (A)

  • Wavelength (λ)

  • Frequency (f)

  • Time Period (T)

Amplitude (A)

• Amplitude is defined as:

  Amplitude is the maximum or minimum displacement from the undisturbed position

• The maximum displacement of a wave is the peak

• The minimum displacement of a wave is the trough

• Amplitude is measured in metres (m)

Wavelength (λ)

• 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

• Wavelength is measured in metres (m)

Graphical representation of transverse waves

• The amplitude and wavelength of a transverse wave can be represented graphically

• The distance along a wave is typically put on the x-axis of a wave diagram

A diagram of a transverse wave

Diagram showing the amplitude and wavelength of a transverse wave

• 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

Frequency (f)

• Frequency is defined as:

  The number of waves passing a point in a second

• Frequency is measured in hertz (Hz)

  • The unit hertz is equivalent to 'per second'

  • 5 Hz = 5 waves per second

• Waves with a higher frequency transfer a higher amount of energy

Time Period (T)

• 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 period  is measured in seconds (s)

• The equation linking frequency and time period is explained in Frequency & time period