Wave Speed Calculator
Solve v = fλ for speed, frequency, or wavelength.
Sound in air ≈ 340 m/s; light in vacuum ≈ 3×10⁸ m/s.
A wave’s speed is frequency times wavelength: v = f × λ. A 170 Hz sound wave with a 2 m wavelength travels at v = 170 × 2 = 340 m/s — roughly the speed of sound in air. Rearrange to f = v ÷ λ or λ = v ÷ f for the other unknowns.
Speed, frequency, and wavelength
Every wave — sound, light, water ripples — obeys one relationship: speed equals frequency times wavelength, v = fλ. Frequency (f) counts how many cycles pass per second in hertz; wavelength (λ) is the distance between successive crests. Multiply them and you get how fast the wave travels.
v = wave speed (m/s), f = frequency (Hz), λ = wavelength (m)
Worked example
A sound wave has a frequency of 170 Hz and a wavelength of 2 m. Find its speed:
- 1 Write the wave equation. v = f × λ, with frequency in hertz and wavelength in metres.
- 2 Substitute the values. v = 170 Hz × 2 m.
- 3 Compute the speed. v = 340 m/s — about the speed of sound in air at room temperature.
Typical wave speeds
Speed depends on the medium; frequency is set by the source, not the medium.
| Wave | Medium | Speed |
|---|---|---|
| Sound | Air (20 °C) | 343 m/s |
| Sound | Water | ~1480 m/s |
| Sound | Steel | ~5960 m/s |
| Light | Vacuum | 3 × 10⁸ m/s |
| Light | Water | ~2.25 × 10⁸ m/s |
Units, media, and common mistakes
One medium, one speed. In a given medium the wave speed is essentially fixed, so raising the frequency shortens the wavelength, and vice versa — they trade off to keep v constant.
Frequency does not change between media. When a wave crosses into a new material its speed and wavelength change, but its frequency stays the same, because it is set by the source.
Common mistake: mixing units. Use hertz and metres to get m/s. If wavelength is in centimetres or nanometres, convert it to metres first.