amplitude

(noun)

The maximum absolute value of some quantity that varies.

Related Terms

  • standing wave
  • transverse wave
  • decibel
  • Restoring force
  • coherent
  • displacement

Examples of amplitude in the following topics:

  • Energy, Intensity, Frequency, and Amplitude

    • The amount of energy in a wave is related to its amplitude.
    • Large-amplitude earthquakes produce large ground displacements, as seen in .
    • Loud sounds have higher pressure amplitudes and come from larger-amplitude source vibrations than soft sounds.
    • In fact, a wave's energy is directly proportional to its amplitude squared because:
    • The energy effects of a wave depend on time as well as amplitude.
  • Interference

    • Interference occurs when multiple waves interact with each other, and is a change in amplitude caused by several waves meeting.
    • In physics, interference is a phenomenon in which two waves (passing through the same point) superimpose to form a resultant wave of greater or lower amplitude.
    • When the waves have opposite amplitudes at the point they meet they can destructively interfere, resulting in no amplitude at that point.
    • By playing a sound with the opposite amplitude as the incoming sound, the two sound waves destructively interfere and this cancel each other out.
    • Pure constructive interference of two identical waves produces one with twice the amplitude, but the same wavelength.
  • Radio Waves

    • The abbreviation AM stands for amplitude modulation—the method for placing information on these waves.
    • The resulting wave has a constant frequency, but a varying amplitude.
    • Thus, since noise produces a variation in amplitude, it is easier to reject noise from FM.
    • (c) The frequency of the carrier is modulated by the audio signal without changing its amplitude.
    • Amplitude modulation for AM radio.
  • Superposition

    • Superposition occurs when two waves occupy the same point (the wave at this point is found by adding the two amplitudes of the waves).
    • The value of this parameter is called the amplitude of the wave; the wave itself is a function specifying the amplitude at each point.
    • Each disturbance corresponds to a force, or amplitude (and the forces add).
    • That is, their amplitudes add.
    • Constructive interference occurs when two waves add together in superposition, creating a wave with cumulatively higher amplitude, as shown in .
  • Forced Vibrations and Resonance

    • As the frequency at which the finger is moved up and down increases, the ball will respond by oscillating with increasing amplitude.
    • Conversely, for small-amplitude oscillations, such as in a car's suspension system, there needs to be heavy damping.
    • Heavy damping reduces the amplitude, but the tradeoff is that the system responds at more frequencies.
    • A child on a swing is driven by a parent at the swing's natural frequency to achieve maximum amplitude.
    • The amplitude of a harmonic oscillator is a function of the frequency of the driving force.
  • Driven Oscillations and Resonance

    • The amplitude A and phase φ determine the behavior needed to match the initial conditions.
    • F_0$ is the driving amplitude and $\!
    • \omega_r = \omega_0\sqrt{1-2\zeta^2}$, the amplitude (for a given $\!
    • For strongly underdamped systems the value of the amplitude can become quite large near the resonance frequency (see ).
    • Steady state variation of amplitude with frequency and damping of a driven simple harmonic oscillator.
  • Impedance

    • where V is the amplitude of the AC voltage, j is the imaginary unit (j2=-1), and $\omega$ is the angular frequency of the AC source.
    • Thus the resistor's voltage is a complex, as is the current with an amplitude $I = \frac{V}{R}$.
    • The amplitude of this complex exponential is $I = j \omega CV$.
    • The magnitude of the complex impedance is the ratio of the voltage amplitude to the current amplitude.
    • We see that the amplitude of the current will be $V/Z = \frac{V}{\sqrt{R^2+(\frac{1}{\omega C})^2}}$.
  • Wavelength, Freqency in Relation to Speed

    • Waves are defined by its frequency, wavelength, and amplitude among others.
    • The first property to note is the amplitude.
    • The amplitude is half of the distance measured from crest to trough.
    • Finally, the group velocity of a wave is the velocity with which the overall shape of the waves' amplitudes — known as the modulation or envelope of the wave — propagates through space.
  • Resonance in RLC Circuits

    • Resonance is the tendency of a system to oscillate with greater amplitude at some frequencies—in an RLC series circuit, it occurs at $\nu_0 = \frac{1}{2\pi\sqrt{LC}}$.
    • Resonance is the tendency of a system to oscillate with greater amplitude at some frequencies than at others.
    • Frequencies at which the response amplitude is a relative maximum are known as the system's resonance frequencies.
    • The driving AC voltage source has a fixed amplitude V0.
  • The Simple Pendulum

    • A simple pendulum acts like a harmonic oscillator with a period dependent only on L and g for sufficiently small amplitudes.
    • Using this equation, we can find the period of a pendulum for amplitudes less than about 15º.
    • If θ is less than about 15º, the period T for a pendulum is nearly independent of amplitude, as with simple harmonic oscillators.
    • For amplitudes larger than 15º, the period increases gradually with amplitude so it is longer than given by the simple equation for T above.
    • For example, at an amplitude of θ0 = 23° it is 1% larger.
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