Amplitude, phase, wavelength and polarization direction
A wave’s pattern speed differs from the motion of its medium.
Key knowledge
A sinusoidal displacement wave can be written y=Acos(kx−ωt+φ), with k=2π/λ and ω=2πf. Its phase advances toward increasing x and its phase speed is ω/k. Transverse displacement is perpendicular to propagation; longitudinal displacement is parallel. Mechanical waves require a medium, while electromagnetic waves can propagate in vacuum.
Values and equations
y=Acos(kx−ωt+φ); k=2π/λ; ω=2πf; v_phase=ω/k
- y,A
- Transverse displacement and amplitude in this example m
- x,λ
- Position and wavelength m
- k
- Wavenumber rad m⁻¹
- ω
- Angular frequency rad s⁻¹
- f
- Frequency Hz
- t
- Time s
- φ
- Initial phase rad
- v_phase
- Phase speed m s⁻¹
Conditions and scope
- A single sinusoidal travelling component, k,ω>0 and a stated physical displacement variable.
- Amplitude units depend on the wave variable; for a pressure wave amplitude is in Pa rather than m. Mixed, dispersive or nonlinear waves need an appropriate model, and transport of a pattern need not imply net transport of medium mass.
Sources · 2
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Samuel J. Ling, Jeff Sanny and William Moebs — OpenStax, Rice University, University Physics (2016)2 sources
- University Physics Volume 1, §16.1: traveling wavesSamuel J. Ling, Jeff Sanny and William Moebs — OpenStax, Rice University, University Physics (2016)Textbook chapter
- University Physics Volume 1, §16.2: mathematics of wavesSamuel J. Ling, Jeff Sanny and William Moebs — OpenStax, Rice University, University Physics (2016)Textbook chapter
Evidence and review
Read §16.1 transverse/longitudinal/medium and amplitude/wavelength definitions, plus §16.2 sinusoidal wave/phase equation16.4. Cosine is a phase-shifted version of the source sine convention; no blanket denial of nonlinear wave mass transport.
2026-10-10 · /root/audit_life_earth_chemistry — independent Chemistry/Life/Earth editor. Independent AI editorial review of this entry's statements, equations, applicability conditions and source coverage. Source checks apply to these claims within their stated limits.
Entry details
Permanent link to this entry ↗- Record identity
- foundation-physics-wave-observables
- Revision
- foundations-refresh.1
- Structured reference record
- Foundational reference additions