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Overview
A wave is a disturbance that transfers energy from one place to another. Some waves require a material medium, such as sound traveling through air or water waves traveling across a surface. Other waves, such as light and other electromagnetic waves, can travel through empty space. Wave properties give physics a precise way to describe these disturbances.
Disturbance and Energy Transfer
A wave is not usually the bulk transport of matter from source to destination. Instead, it is a pattern of disturbance that carries energy. Particles of a medium may move locally while the wave pattern travels across a larger distance.
Amplitude
Amplitude measures the size of the disturbance from equilibrium. Larger amplitude usually corresponds to greater energy carried by the wave, although the exact relationship depends on the type of wave.
Wavelength
Wavelength is the distance between corresponding points on neighboring cycles of a wave, such as crest to crest, trough to trough, or compression to compression.
Frequency and Period
Frequency is the number of cycles passing a point each second. Period is the time required for one complete cycle. Frequency and period are inversely related.
Wave Speed
Wave speed describes how quickly the disturbance travels. It depends on the type of wave and the properties of the medium or field through which the wave travels.
Transverse Waves
In a transverse wave, the disturbance is perpendicular to the direction of wave travel. Waves on strings and many electromagnetic wave representations are treated as transverse.
Longitudinal Waves
In a longitudinal wave, the disturbance is parallel to the direction of wave travel. Sound in air is a common longitudinal wave with compressions and rarefactions.
Medium
A medium is the material through which a mechanical wave travels. Air, water, metal, rope, and Earth materials can act as media. Electromagnetic waves do not require a material medium.
Common Mistakes
A common mistake is thinking the medium moves permanently with the wave. In most mechanical waves, the medium oscillates locally while energy travels through it.
Why This Matters in Physics
Wave properties are the foundation for sound, light, optics, communication, vibration, resonance, interference, standing waves, and electromagnetic radiation.