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
