Amplitude and intensity are two important properties that describe waves, but they represent different aspects of a wave's magnitude. Amplitude relates to the maximum displacement of a wave, while intensity relates to the power carried by a wave per unit area.
Amplitude is the maximum displacement of a point on a wave from its equilibrium (rest) position. It's essentially the 'height' of the wave. For transverse waves, like light waves, it's the maximum displacement of the electric or magnetic field. For longitudinal waves, like sound waves, it's the maximum displacement of the particles in the medium from their resting positions.
Intensity is the power carried by a wave per unit area. It describes how much energy the wave is transporting. Intensity is proportional to the square of the amplitude. The formula that ties these together is: $I \propto A^2$, where $I$ is the intensity and $A$ is the amplitude.
| Feature | Amplitude | Intensity |
|---|---|---|
| Definition | Maximum displacement from equilibrium | Power per unit area |
| Units | Meters (m) for mechanical waves; Volts/meter (V/m) for electromagnetic waves | Watts per square meter (W/m²) |
| Relationship | Direct measure of displacement | Proportional to the square of the amplitude ($I \propto A^2$) |
| Perception (Sound) | Related to loudness | Related to loudness; more objective measure |
| Perception (Light) | Related to brightness | Related to brightness; more objective measure |
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