3.3.1.1
Five quantities define any progressive wave
Progressive Waves — AQA A-Level Physics
Key Definition
Displacement (x) — The distance of a point on the wave from its equilibrium position. A vector quantity measured in metres (m); can be positive or negative.
Key Definition
Amplitude (A) — The maximum displacement of a particle in the wave from its equilibrium position. Measured in metres (m).
Key Definition
Wavelength (lambda) — The distance between points on successive oscillations of the wave that are in phase. Measured in metres (m).
Key Definition
Period (T) — The time taken for one complete oscillation or cycle of the wave. Measured in seconds (s).
Key Definition
Frequency (f) — The number of complete oscillations per unit time. Measured in hertz (Hz) or \(s^{-1}\).
Examiner Tips and Tricks
- When labelling wavelengthThe minimum distance between two points on a wave that are in phase (e.g. crest to crest). Measured in metres (m). on a diagram, your arrows must go from the very top of one crest to the very top of the next.
- If your arrow is too short, you lose marks.
- The same applies to amplitudeThe maximum displacement of a point on a wave from its equilibrium (rest) position. Measured in metres (m). -- draw it from the equilibriumAn object is in equilibrium when the resultant force on it is zero. The object is either stationary or moving at constant velocityThe rate of change of displacement. A vector quantity. Measured in m s⁻¹.. to the peak, not from trough to peak.