Edexcel IGCSE Physics 复习笔记 3.1.2 Describing Wave Motion

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

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