Table of Contents
What Is Wave Speed?
Wave speed is the rate at which a wave disturbance propagates through a medium. It depends on the medium's physical properties (density, elasticity, temperature), not on the wave's amplitude or frequency. Sound travels faster through denser, stiffer media like steel (5,960 m/s) compared to air (343 m/s).
The wave speed equation connects three fundamental wave properties. Knowing any two of frequency, wavelength, and speed lets you calculate the third. This relationship applies universally to electromagnetic waves, sound waves, water waves, and seismic waves.
The Formula
Where v is wave speed (m/s), f is frequency (Hz), and λ is wavelength (m). For electromagnetic waves in vacuum, v = c = 299,792,458 m/s. For sound in air at 20°C, v ≈ 343 m/s.
Speed of Sound in Various Media
| Medium | Speed (m/s) | Speed (ft/s) |
|---|---|---|
| Air (20°C) | 343 | 1,125 |
| Water (25°C) | 1,497 | 4,911 |
| Seawater | 1,531 | 5,023 |
| Steel | 5,960 | 19,554 |
| Diamond | 12,000 | 39,370 |
Frequently Asked Questions
Why does sound travel faster in water than air?
Despite being denser, water has a much higher bulk modulus (resistance to compression) than air. The speed of sound depends on the ratio of bulk modulus to density, and water's stiffness dominates, resulting in sound traveling about 4.3 times faster in water.
Does temperature affect wave speed?
For sound in air, speed increases about 0.6 m/s per degree Celsius rise. At 0°C it is 331 m/s; at 20°C it is 343 m/s. For light in vacuum, speed is constant regardless of temperature or any other condition.
What determines wave speed on a guitar string?
Wave speed on a string equals the square root of tension divided by linear mass density: v = √(T/μ). Tighter strings and thinner strings produce higher wave speeds and therefore higher-pitched notes for the same string length.