What is the speed of sound in air and how does it relate to frequency and wavelength?

Sound travels at about 343 m/s in air at 20 C. For a 343 Hz tone, lambda = v/f = 343/343 = 1 m. For 1000 Hz, lambda = 0.343 m.

Does the speed of a wave change when it crosses from one medium to another?

Yes. The speed changes because the medium's properties (density, elasticity for sound; permittivity, permeability for light) change. The frequency stays the same (it is set by the source), so the wavelength changes proportionally.

Can I use v = f*lambda for light?

Yes. In a vacuum, light travels at c = 3 x 10^8 m/s. For green light at f = 5.5 x 10^14 Hz, lambda = c/f approximately 545 nm. In glass, v decreases so lambda shortens while f stays the same.

Wave Speed Calculator

Calculate the speed of a wave using v = fλ. Enter frequency and wavelength to find wave speed in metres per second, applicable to sound, light, water waves, and any periodic disturbance.

By AbraCalc Editorial Team · Reviewed by AbraCalc Methodology Review · Last reviewed: 2026-06-25

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How to use this tool

Enter frequency (f) and wavelength (λ) in the fields above.
Results update instantly as you type — or click Calculate.
Read your wave speed and the full breakdown beneath it.

Formula

v = f × λ

How it works

Multiply frequency (Hz) by wavelength (m) to get wave speed (m/s).

Worked example

Common mistakes to avoid

Confusing wavelength (distance between crests) with amplitude (height of crest) — amplitude does not appear in the wave speed formula.
Using frequency in kHz or MHz without converting to Hz when wavelength is in metres, giving wave speeds that are off by a factor of 1000 or more.
Assuming wave speed is constant in all media — v = f*lambda holds, but changing medium changes v, which changes lambda while f remains the same (set by the source).

Key terms

Frequently asked questions

What is the speed of sound in air and how does it relate to frequency and wavelength?: Sound travels at about 343 m/s in air at 20 C. For a 343 Hz tone, lambda = v/f = 343/343 = 1 m. For 1000 Hz, lambda = 0.343 m.
Does the speed of a wave change when it crosses from one medium to another?: Yes. The speed changes because the medium's properties (density, elasticity for sound; permittivity, permeability for light) change. The frequency stays the same (it is set by the source), so the wavelength changes proportionally.
Can I use v = f*lambda for light?: Yes. In a vacuum, light travels at c = 3 x 10^8 m/s. For green light at f = 5.5 x 10^14 Hz, lambda = c/f approximately 545 nm. In glass, v decreases so lambda shortens while f stays the same.