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Overview
Wave speed is the rate at which a wave disturbance travels. It is not necessarily the same as the speed of the particles in the medium. In many mechanical waves, particles oscillate locally while the wave pattern moves through the medium.
Core Relationship
Wave speed is related to frequency and wavelength. If a wave repeats more often and each cycle has a certain length, the disturbance travels at a speed determined by how many wavelengths pass per second.
Medium Properties
For mechanical waves, wave speed depends on the properties of the medium. Tension, density, elasticity, temperature, and stiffness can affect how quickly a disturbance travels.
Speed of Sound
Sound speed depends on the medium. Sound travels through air, liquids, and solids at different speeds because the particles and elastic properties of those materials differ.
Speed of Light
Light and other electromagnetic waves travel at a fixed speed in vacuum and at slower speeds in materials. This difference in speed helps explain refraction.
Particle Motion vs. Wave Motion
The particles of a mechanical wave do not usually travel with the wave from start to finish. They oscillate around local positions while the energy and disturbance move across the medium.
Changing Medium
When a wave enters a new medium, its speed may change. Frequency often remains tied to the source, while wavelength changes to match the new speed.
Graphs and Measurement
Wave speed can be studied by measuring distance traveled over time, or by using wavelength and frequency. Graphs of wave motion can help identify repeated features and travel time.
Common Mistakes
A common mistake is assuming higher frequency always means higher wave speed. In a given medium, changing frequency often changes wavelength while speed remains determined by the medium.
Applications
Wave speed matters in acoustics, seismology, optics, sonar, radio, communications, medical ultrasound, and materials testing.
Why This Matters in Physics
Wave speed connects wave geometry, timing, medium properties, and energy transfer. It is essential for sound, light, seismic waves, and communication systems.