Does the calculator determine wave speed from a material name?

No. Use a phase speed documented for the actual wave type,mode,direction,frequency and conditions. The calculator only applies lambda equals phase speed divided by frequency.

Is the vacuum electromagnetic-wave speed exact?

Yes. In that mode the calculator uses the SI fixed value c equals299792458 metres per second for light in vacuum.

General periodic-wave relation

Documented Phase-Speed Wavelength Calculator

Calculate wavelength and related quantities from frequency and a documented phase velocity,or use the exact SI speed of light for an electromagnetic wave in vacuum.

v_p=fλk=2π/λReference arithmetic — no material-property lookup

Wave quantities

Długość fali λ

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Wavelength in metres

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Period T

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Spatial angular wavenumber k

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Ordinary wavenumber 1/λ

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Angular frequency ω

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Normalized frequency

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Phase speed used

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Implemented relations

v_p=fλ → λ=v_p/f
T=1/f
k=2π/λ (rad/m)
ν̃=1/λ (cycles/m)
ω=2πf (rad/s)

f is frequency in hertz,v_p is phase speed in metres per second,λ is wavelength in metres,T is period in seconds,k is spatial angular wavenumber,and ν̃ is ordinary spatial frequency. Dimensional check:(m/s)/(1/s)=m.

Primary references

OpenStax University Physics,Volume1,Chapter16 key equations gives v=λ/T=λf,k=2π/λ and v=ω/k. BIPM SI Brochure,9th edition,Appendix2 v1.2 (19June2026) states the fixed vacuum speed c=299792458m/s.

Why there is no material drop-down

A single label such as “steel”,“aluminium”,“concrete”,“water” or “air” does not fully define phase speed. Elastic-wave speed depends on wave family and material properties; structural and guided waves may be dispersive. Fluid/gas speeds depend on state and composition. Use project data for the relevant mode,direction,frequency and conditions. The vacuum mode is the only built-in speed because c is an exact SI defining constant.

No acceptance or detectability claim

The result is general wave arithmetic,not an ISO calculation and not a defect-size,sensor-spacing or structural-mode criterion. Ultrasonic detectability and vibration sensor placement depend on the complete measurement and propagation problem,not wavelength alone.