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Amplitude facts for kids

Kids Encyclopedia Facts
In this picture, y is the amplitude of the wave
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Different kinds of amplitudes

The amplitude or peak amplitude of a wave is a measure of how big its oscillation is.

Amplitudes are always measured as positive numbers (for example: 3.5, 1, 120) and are never negative (for example: -3.5, -1, -120). That's because distance can only be greater than zero or equal to zero; negative distance does not exist.

The distance from the top of one peak to the bottom of another is called peak-to-peak amplitude. Another way to describe peak-to-peak amplitude is to say that it is the distance between the maximum positive value and the maximum negative value of a the maximum displacement of a wave from an equilibrium position.


The units of the amplitude depend on the type of wave, but are always in the same units as the oscillating variable. A more general representation of the wave equation is more complex, but the role of amplitude remains analogous to this simple case.

For waves on a string, or in a medium such as water, the amplitude is a displacement.

The amplitude of sound waves and audio signals (which relates to the volume) conventionally refers to the amplitude of the air pressure in the wave, but sometimes the amplitude of the displacement (movements of the air or the diaphragm of a speaker) is described. The logarithm of the amplitude squared is usually quoted in dB, so a null amplitude corresponds to − dB. Loudness is related to amplitude and intensity and is one of the most salient qualities of a sound, although in general sounds it can be recognized independently of amplitude. The square of the amplitude is proportional to the intensity of the wave.

For electromagnetic radiation, the amplitude of a photon corresponds to the changes in the electric field of the wave. However, radio signals may be carried by electromagnetic radiation; the intensity of the radiation (amplitude modulation) or the frequency of the radiation (frequency modulation) is oscillated and then the individual oscillations are varied (modulated) to produce the signal.

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See also

Kids robot.svg In Spanish: Amplitud (física) para niños

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