amplitude (ămˈplĭtōdˌ) [key], in physics, maximum displacement from a zero value or rest position. In the harmonic motion of a pendulum, the amplitude of the swing is the greatest distance reached to either side of the central rest position. Amplitude is important in the description of a wave phenomenon such as light or sound. In general, the greater the amplitude of the wave, the more energy it transmits (e.g., a brighter light or a louder sound).
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