Wave Speed
Sound speed equals frequency times wavelength.
Formula
Variables
Example
440 Hz in air (343 m/s): λ = 343/440 ≈ 0.78 m
How it works
A wave travels by passing repeating crests or compressions through space, and each cycle takes one period to complete. In one second, the number of cycles that pass a point is the frequency, and each cycle occupies one wavelength, so the distance covered per second is frequency multiplied by wavelength. That is why wave speed depends on both how often the wave repeats and how far apart the repeats are.
When to use it
Use this formula whenever you know any two of wave speed, frequency, and wavelength and need the third. It is especially useful in sound, string vibrations, and other basic wave problems in music and acoustics.
Worked example, step by step
A tuning fork produces a sound with frequency 256 Hz, and the wavelength in air is 1.34 m. Use v = fλ v = 256 × 1.34 v = 343.04 m/s Final answer: the wave speed is about 343 m/s
Common mistakes to avoid
- Using the wrong units, such as frequency in kHz without converting to Hz
- Rearranging the formula incorrectly when solving for wavelength or frequency
- Forgetting that wavelength is a distance in metres, not a number of cycles
Did You Know?
Sound travels about 343 m/s in air but roughly four times faster in water and fifteen times faster in steel.
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