What is Amplitude: Definition and 866 Discussions

The amplitude of a periodic variable is a measure of its change in a single period (such as time or spatial period). There are various definitions of amplitude (see below), which are all functions of the magnitude of the differences between the variable's extreme values. In older texts, the phase of a period function is sometimes called the amplitude.

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  1. J

    How get amplitude and phase as a function of time?

    Given a function of the time like ##f(t)##, its Fourier transform is ##F(\nu)## and by definition, ##Abs(F(\nu))=A(\nu)## and ##Arg(F(\nu)) = \varphi(\nu)##, so I have amplitude and phase as function of the frequency, but make sense speak in amplitude and phase as function of the time? If yes...
  2. O

    Average power in Amplitude Modulation

    Homework Statement how the overall power becomes lesser when one side band is taken away by the bandpass filter and also how it limits the bandwidth of the signal Homework Equations The Attempt at a Solution there is will be the trade off between power and bandwidth. Vdc and Vm...
  3. M

    A capacitor in an AC circuit. What is the amplitude of the current?

    A capacitor in an AC circuit. What is the amplitude of the current?? Homework Statement I really do not know how to approach this problem. What confuses me is that when calculating the % error I'm suppose to have a theoretical or accepted value and a measured value. So how do I determine...
  4. B

    Deriving wave equation with single string and small amplitude wave.

    1.This equation in the link below refers to the small angle approximation regarding deriving the wave equation from Newtons laws from small amplitude waves in a single string with fixed tension. 2.http://imgur.com/NGSwzcl 3. I'm a bit rusty on the maths and have no idea how these...
  5. J

    Complementary jacobi amplitude

    I found this identity in the wiki https://de.wikipedia.org/wiki/Jacobische_elliptische_Funktion#Abstrakte_Definition_als_spezielle_meromorphe_Funktionen One propertie of the ellipitc integral is: K(k') = K'(k), all this set of ideia seems answer an old doubt, ie, exist a complementary...
  6. A

    The amplitude of sound waves from two nearby speakers

    Homework Statement In the figure below, two speakers S1 and S2 emit sound waves of wavelength 2m, in phase with each other. Let Ap be the amplitude of the resulting wave at point P, and Aq be he amplitude of the resultant wave at point Q. How does Ap compare to Aq? a. Ap<Aq b. Ap=Aq c...
  7. B

    The Relationship Between Wavelength and Amplitude of Photons and Electrons

    Is there a relation between the wavelength and the amplitude of a photon (or particle), or all frequencies have the same amplitude? If the latter, why the wavelength affects the way a radiation passes through matter or slits? Thanks.
  8. J

    Delta amplitude and nabla amplitude

    Delta amplitude and "nabla amplitude" Why all jacobi theory and all ellipitc integrals is based in ##\Delta(\theta) = \sqrt{1-m \sin(\theta)^2}## ? You already think that this definition is just midle of history, cause' you can define other elementar function: \nabla(\theta) = \sqrt{1-m...
  9. P

    Simple Harmonic Motion amplitude problem

    Homework Statement An object is undergoing simple harmonic motion with frequency f = 3.1 Hz and an amplitude of 0.15 m. At t = 0.00 s the object is at x = 0.00 m. How long does it take the object to go from x = 0.00 m to x = 7.00×10-2 m. Homework Equations x(t)=Asin(ωt) The Attempt...
  10. M

    Amplitude dependencies in an oscillator

    I know amplitude doesn't depend on mass but I came across a problem where the amplitude changed with a change in mass. The problem was a horizontal frictionless spring with a box of mass m1 attached to it with a stone of mass m2 inside of the box. At its equilibrium point at its maximum...
  11. P

    Probability and probability amplitude

    |A>=a|0>+b|1> <A|A>=probability amp |<A|A>|^2=probability If the state is same, so <A|A>= a^2+b^2=1. then i find the probability and no interference term in it! so can i say <A|A>=|<A|A>|^2 and no square is needed? since if i square it become a^4+b^4=?? what wrong with it! and where...
  12. N

    Attenuation finding distace and amplitude

    Homework Statement problem 1 A 20 Hz seismic wave traveling at 3 km/s propagates for 2000 m from point X to point Y through a medium with an attenuation rate of 0.5 dB/λ. What is the ratio between the amplitude of the wave measured at X and the amplitude of the wave measured at Y (i.e., AX/AY)...
  13. K

    Amplitude modulation - why is ωc ωm necessary?

    amplitude modulation -- why is ωc >> ωm necessary? i just want to ask why is ωc >> ωm is necessary for a good amplitude modulation
  14. 6c 6f 76 65

    Harmonic oscillation; new amplitude?

    Homework Statement A block with a mass M is located on a frictionless, horizontal surface and is attached to a horizontal spring with spring stiffness k. The block is being pulled out to the right a distance x=x_0 of equilibrium and released at t = 0. At time t_1, corresponding to \omega...
  15. R

    Understanding the Relationship between Amplitude and Frequency in Waves

    Hi everyone. The answer to the question about the relationship between amplitude and frequency is usually that they are independent of each other. Pardon the imprecision of my language, for I am not a physicist. I'll try my best to be clear. The amplitude of a wave is a measure of the distance...
  16. S

    Typical carrier frequency for amplitude modulation

    What is a typical carrier frequency for amplitude modulation? In particular, for amplitude modulation in spectroscopy.
  17. P

    Intensity, frequency and amplitude

    Homework Statement A wave has an amplitude a1, intensity I, and frequency f. A second wave of the same type has twice the intensity and double the frequency, find the amplitude of the second wave in terms of a1. Homework Equations Using the relationship I=k a2f2, where k is a constant...
  18. tfr000

    What is the formula for two (or more) tone amplitude modulated signal?

    So far I have: V=Acarriersin(2∏Fcarriert) (1+Cmodsin(2∏F1t)+Cmodsin(2∏F2t)) which I think is pretty close to correct. Where: A is amplitude, F is freq, t is time, Cmodis the coefficient of modulation, i.e. 1=100% modulation. I can find plenty of websites offering 1-tone AM, but not 2 or more...
  19. B

    Probability Amplitude Maxwell's Equations

    Hello Everyone, I am currently reading page 20 of Townsend's Quantum Physics book. Here are a few sentences that I am unsure of: "In general, the magnitude and phase of the probability amplitude are determined from first principles by solving Maxwell's equations. In free space, these...
  20. J

    Why Does Fundamental Freq Have Largest Amplitude?

    Please could somebody explain why the fundamental frequency always has the biggest amplitude in comparison to the rest of the harmonics?
  21. A

    Microwave oven EM wave amplitude

    I don't really know how to quantify EM waves when it comes to amplitude, but I understand that MRI rf waves are measured in units of tesla. What is the amplitude of a typical microwave oven EM wave in Tesla (mT, uT)??
  22. M

    Maximum amplitude of second order system

    See attached for the problem and attemped solution, its is not an applied problem, just a theoretical problem.
  23. D

    Understanding Probability Amplitude, State Operators and Galilei Group

    Greetings, Just checking if I'm getting this ... please correct me if I'm wrong. The value of the wavefunction is 'probability amplitude' in discrete case and 'probability amplitude density' in continuous case. The former is a dimensionless complex number and the latter is the same...
  24. Jilang

    Why is probability amplitude squared?

    Does anyone have an intuitive understanding of why probabilities in QM are the amplitudes multiplied by their compex conjugates?
  25. A

    Exploring the Concepts of AM Modulation

    AM amplitude modulation--- Hi everyone, I am learning AM recently, but I have some question that keep troubling me.. 1. We know that AM wave is produced by the multiplication of carrier wave and modulation wave. But why does the equation of AM wave is not a direct multiplication of Vm×Vc...
  26. P

    Two wave superposition with different wavelength , amplitude and frequ

    Homework Statement Hi Two wave superposition with different wavelength , amplitude and frequency u1(x,t)=A1cos(k1x+w1t) u2(x,t)=A2cos(k2x+w2t) a)Show that an amplitude modulation is obtained Homework Equations No relevant equations The Attempt at a Solution...
  27. M

    Discretion and harmonic amplitude

    What's the relationship between DFT and harmonic amplitude? How do I find the harmonic amplitude using discrete Fourier transform? Here's what I have done so far. "harm.freq" is harmonic frequency here. I have done the DFT calculation and now what? Aftet I have performed DFT, how do I find the...
  28. M

    Electricity circuit question, amplitude resistor?

    Homework Statement The ac circuit has 3 components in series: a Capacitor C=120μF, an Inductor L=100mH, and a resistor R=7Ω. A) Find the amplitude of the voltage across the resistor R in the LCR circuit below, when operated at a frequency of 45 Hz? B) What is the phase difference...
  29. P

    What is the equation for the amplitude of scalar perturbations ?

    What is the "equation for the amplitude of scalar perturbations"? I am studying inflation now, and in a book I read "equation for the amplitude of scalar perturbations", in the paper the author does not explain what is it, could anyone give some detail on this equation or any reference? Thanks...
  30. M

    What does 0 amplitude mean in waves and quantum physics?

    When a wave for light or an electron is represented on a graph, it is shown with the y-axis representing amplitude. Now, these waves cross the x-axis (where amplitude=0) but what does this actually mean, for that instant? Is it that the wave is no longer observed for that instant? Also, since...
  31. D

    Triangle wavefunction - position uncertainty and probability amplitude

    Homework Statement Hey guys. Basically I have a wavefunction that looks like this http://imageshack.com/a/img843/3691/22r3.jpg I have to find: (a) The normalization constant N, of course by normalizing it (b) Find <x> and <x^2> and use this to find Δx. Homework Equations I'm just...
  32. K

    Initial momentum amplitude to wave function

    Homework Statement http://www.whoisntdavidrinaldi.com/Untitled.png Homework Equations The Attempt at a Solution So I had to use this initial momentum and multiply it by a plane wave (sure you are aware of the exp[i(px+p^2(t)/2m)\hbar] ) setting p-p_0 to q and then coupling all terms...
  33. B

    Saw-tooth Wave and Fourier Series amplitude of oscillation

    Homework Statement An oscillator with free period \tau is critically damped and subjected to a force with the saw-tooth form \F(t)=c(t-n\tau) for (n-0.5)\tau<t<(n+0.5)\tau for each integer n. Find the amplitudes a_n of oscillation at the angular frequencies 2\pi n/\tau if c is a...
  34. G

    What determines an amplitude of a wave particle?

    According to Bohr's model, photon is emitted when electron "falls" to the lower level with energy equal to the difference between energies on these levels. This determines the frequency of the photon. What determines an amplitude of a wave created by a single photon, or electron?
  35. C

    Finding the amplitude of the sum vector

    Homework Statement A signal E(t) is made up of three terms, each having the same frequency but differing in phase: E(t) = E0cos(ωt) + E0cos(ωt + δ) + E0cos(ωt + 2δ) It is possible to find the amplitude of the sum vector by summing each vector described as a magnitude multiplied by a...
  36. D

    Calculating the amplitude that a particle is spin up

    The wavefunction for a spin 1/2 particle is a spinor field of the form \psi(\mathbf{x},t)=\left( \begin{array}{cc} \psi_{+}(\mathbf{x},t)\\ \psi_{-}(\mathbf{x},t) \end{array} \right). \psi_{+}(\mathbf{x},t) is the amplitude that the particle is both spin up and located at position x at time...
  37. J

    Why do particles have non-zero position amplitude across all space?

    I keep coming across the claim that it is a consequence of the Schrodinger dynamics, that even if one postulates wave-function-collapse, so that the wave-function for a particle is entirely confined within some small region at the moment of collapse, an instant later the wave-function will have...
  38. J

    What does a sound wave amplitude physically consist of?

    Frequency is pitch. Or how fast it oscillates. So what does the amplitude translate to in physical space? I know its volume, or the amount of energy. But what does it actually do to the air when you increase the amplitude?
  39. H

    Finding Amplitude and Phase of Complex Functions

    I can't seem to remember how to find the amplitude/phase of a complex function (I do know what to do for complex numbers, though). I know it's in my mind somewhere, but I just can't remember lol. So, for example, how would I find the amplitude/phase of: 3+j5t and 3ej4t EDIT: I know for...
  40. F

    Amplitude and frequency dependence on energy of a wave.

    Hello all, I have learned that the energy of a wave is proportional to the square of its amplitude. I have also learned (by the Planck relation) that the energy of a wave is proportional to the frequency of the wave. Doesn't this imply that the frequency of a wave is proportional to the square...
  41. G

    What is the relationship between intensity and amplitude in waves?

    This is something I don't relly get. I keep reading that the intensity of a wave is proportional to the square of its amplitude. So let's suppose we have a random wave source, with amplitude A0. If we replace that source with five identical copies of it, their collective amplitude is 5A, yes...
  42. S

    Intuition behind probability amplitude calculations?

    Why is the probability of a particle being at a certain location proportional to the square of of "the" amplitude? What does "the" in that sentence represent more specifically? Why are amplitudes complex numbers? Any intuition or clarification would be very appreciated. Thanks!
  43. G

    Find amplitude and frequency given positions and speeds

    Homework Statement I'm working my way through Classical Mechanics by J.R. Taylor. I'm stumped by the one-star ("easiest") Problem 5.11: "You are told that, at known positions x1 and x2, an oscillating mass m has speeds v1 and v2. What are the amplitude and angular frequency of the...
  44. S

    Contradiction in Wave Amplitude, intensity and Conservation of Energy?

    Hi guys, let's say we have a wave where the power P is proportionate to the square of its amplitude, which is A^2. If now we have 2 identical waves in superposition in phase, then we have an amplitude of 2A am i right? Next, we realize that because of the amplitude of the superposed waves is...
  45. I

    What is the amplitude of an EM wave?

    i always hear about the frequency/wavelength, and the speed of the wave, but i never heard about the actual amplitude of the wave itself? how would one derive this? I'm not referring to intensity... intensity deals with the number of photons being captured by a detector... I'm referring to the...
  46. AJKing

    Amplitude of a Damped, Driven Pendulum

    Homework Statement A simple pendulum has a length of 1m. In free vibration the amplitude of its swings falls off by a factor of e in 50 swings. The pendulum is set into forced vibration by moving its point of suspension horizontally in SHM with an amplitude of 1 mm. a) [... Built Differential...
  47. D

    Putting phase factor in amplitude in Lorentz oscillator

    Hi there, In my course solid state physics, there is a part about the Lorentz oscillator. At a certain part, this is written: "X(t) = X_0sin(-ωt+α) This changes into: X(t) = X_0 exp(-iωt) by choosing X_0 as a complex number and putting the phase factor into the complex amplitude."...
  48. G

    Finding amplitude from a diagram

    Hi all, This is not homework or coursework. I am not sure whether this question would be classed as homework or coursework because it is neither. I am using the AQA Physics A AS textbook and attempting exercise 12.2 on page 177. In I am stuck on question 4 and I have absolutely no idea on...
  49. B

    Simple pendulum, changing amplitude vs changing the length of string

    Hello, I don't understand how changing the amplitude does not change the period but changing the length of the string does. Each changes the height and changes the arc length so wouldn't they both change the period? Thank you for any help!
  50. K

    Large Amplitude Solutions in a forced massed spring system

    "Large Amplitude Solutions in a forced massed spring system" Homework Statement Using the formula, y"+by'+k1*y+k2*h(y) = -10 +0.1sin(ωt) In the previous part of the of this "lab", I had to use some conditions for b, k1, k2, and ω, and analytically solve the problem and compare the graphs...
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