Amplitude Definition and 868 Threads

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. M

    What is the correct code for plotting an amplitude spectrum in MATLAB?

    i am trying to plot the amplitude spectrum for a function which has the following properties: f(t) = 1, 0 < t < 10 f(t) = 0, 10 < t < 20 the period of the function is 20 i found the Fourier coefficients to be Fn = -(1/n*pi)(cos(n*pi) - 1) i tried to use the following code to plot the...
  2. E

    : precalc project amplitude help

    URGENT: precalc project amplitude help! Homework Statement I am doing a project for my precalc class which explores the applications of sine waves in real life. I chose to do bat and dolphin echolocation. so far the information i have found online has given me frequency in Hz, length of each...
  3. F

    Scalar particle scattering amplitude

    Homework Statement I have simplified the expression -i\int d^4xie[\phi'^*(\partial_{\mu}A^\mu + A^\mu\partial_\mu)]\phi to -i\int d^4xie[\phi'^*(\partial_\mu\phi) - (\partial_\mu\phi'^*)\phi]A^\mu under the conditions A^0 \rightarrow 0, t \rightarrow \pm \infty |A^i| \rightarrow 0, |x_i|...
  4. T

    Why Is There a Negative Sign in the Differential Cross Section?

    I have a process that a scalar and a photon at the final state. When we take the complex conjugate and sum over photon final polarization state...it give negative sign in the differential cross section...what does this mean? the trace didn't give negative value. M=M^{\mu}\cdot\epsilon_{\nu}...
  5. P

    Relationship between harmonics and wave amplitude

    What is the relationship between harmonics and wave amplitude in a resonant object? Lets say we have an object which has a natural resonant frequency of 50hz. we connect that object to a signal generator set at 50hz and note the amplitude of the oscillations the object. Next we go up one...
  6. M

    Fourier Coefficient Amplitude: Is Infinity Possible?

    Is it possible to have an infinite value for the amplitude of a Fourier coefficient? The signal is sin(w0t) from 0 to T/2. My resulting coefficient formula was Fn = 2/[4pi(1-n)] + 2/[4pi(1+n)] so for F1 i got infinity ... is this possible? or is coefficient just wrong?
  7. N

    Amplitude Modulation: Sine Wave Carrier of 750kHz, 4.0V, Modulated by 3kHz, 0.5V

    Hi everyone, plx help me on this! I've worked out frequency modulation but can't understand amplitude modulation ... A sinusoidal carrier wave has a frequency of 750kHz and an unmodulated amplitude of 4.0V. The carrier wave is to be amplitude-modulated by a sinusoidal signal of frequency...
  8. H

    What is the amplitude of an oscillating spring with a 185g mass at 5.2Hz?

    Homework Statement a 185g mass attached to a horizontal spring oscilates at 5.2Hz. At t=0s, the amss is at x=5.80 and has a vx=-40.0cm. determine the amplitude Homework Equations The Attempt at a Solution
  9. A

    Reflection of a Wave: Amplitude, Frequency, Velocity

    Homework Statement 1. When a wave is reflected from a mirror, there is no change in its a) Amplitude b) Frequency c) Velocity d) All Homework Equations The Attempt at a Solution I think frequency changes,not sure
  10. D

    Amplitude of a block oscillating on a spring

    Homework Statement a .25kg block oscillates on the end of a spring with a spring constant of 200N/m. If the oscillation is started by elongating spring to 0.15m and giving the block a speed of 3.0m/s. The amplitude is? Homework Equations omega= sqrt(k/m), Vm = (omega)Xm The Attempt...
  11. C

    Predicted Amplitude for Standing Waves on a String: Can It Be Calculated?

    Homework Statement One end of a string is attached to a vibrating "reed" that vibrates at 120 Hz. The other end is passed along a pulley stationed 1 meter away from the vibrating reed. Different masses are hung from the end of the string that passes over the pulley in order to create a...
  12. A

    What is the Amplitude of an Electron's Oscillation in AC Household Current?

    Homework Statement In a typical household current, the electrons in the wire may have a drift speed of 1.3×10−4 m/s. Actual household current is not a direct current, but instead is an alternating (oscillating) current. (If you have ever received an electric shock from an outlet, you have...
  13. J

    Pendulum amplitude after 5 minutes

    Suppose one pendulum consists of a 1-meter string with a bob that is an aluminum sphere 2 inches in diameter. A second pendulum consists of a 1-meter string with a bob that is a brass sphere 2 inches in diameter. The two pedulums are set into oscillation at the same time and with the same...
  14. C

    Scattering Amplitude in Canonical Quantization

    Hi there, I have little question: reading zee 2nd edition, I.8 (pag 64) i came up with this: start with <k_1 k_2| e^{-iHT}| k_3 k_4> and H=H_0 +u u=\lambda \int \phi^4 where H_0 is the usual hamiltonian for the free scalar field. Then, zee says that "expanding in \lambda, we obtain...
  15. R

    Accelerometer to Frequency and Amplitude

    I have a spreadsheet of Accelerometer data out of an iPhone and I have calculated the displacement in the three axis. I would like to figure out how to take this info and calculate the frequency, avg. amplitude, and the highest amplitude. Excel has a frequency function but I would like to...
  16. V

    Wave Problem - Amp, Freq, Vel & Wave Length

    Homework Statement The displacement function for a string carrying a transverse wave is y(x, t) = 2.0mm*sin(20*x/m − 600*t/s) Determine the amplitude, frequency, velocity and wavelength of the wave. Determine the maximum transverse speed of any point on the string. Homework...
  17. D

    Confidence intervals of amplitude and phase for a noisy sine wave

    Homework Statement I have two series of data consisting of samples of a noisy sine wave and need to determine the amplitude and phase and the confidence intervals. I determined the amplitude and phase but don't know how to calculate the confidence intervals, help! The Attempt at a Solution By...
  18. B

    What are the measurements for amplitude and wavelength of a radio wave?

    Homework Statement So I have to make a snapshot & history graph of a wave. I chose to do a radio wave. However, I just want to know what the measurements for amplitude and wavelength. Also, there's no specific way to draw a snapshot of a radio wave is there? I can just draw the wave...
  19. S

    How Can Amplitude Decay be Modeled with a Pendulum and Friction Coefficient?

    Basic premise: a pure tone sine wave can be modeled with a pendulum and the rate of amplitude decay can be manipulated with a friction coefficient. So... does anyone know how this is actually done? In other words if you picked a pure tone (let's say middle C @ 261.6 Hz) initiated at a certain...
  20. A

    Amplitude Normalization of Electromagnetic Waves

    I've two electromagnetic waves (light) with amplitudes 1x (normal) and 2x (double) amplitude. And I want to pass these two waves through a "normalizer" expecting 1x amplitude for both waves. Question is: Is such a "normalizer" possible and/or exists. I'm not looking for any electronic...
  21. F

    What Determines the Physical Size of a Radio Wave's Amplitude?

    hey do you know how to calculate what is the physical size of the amplitude of a radio wave? like I know how to calculate the wavelength but to draw a scale physical representation of that wave in space, how do I use amplitude to calculate the (y axis) height of the peak periods?
  22. T

    Calculating Amplitude of Mass on Spring on Frictionless Surface

    mass attached to spring on horizontal frictionless surface. given: position x at time zero, velocity at time zero (not equal to zero), spring constant, and mass. how do I figure out the amplitude?
  23. M

    Quantum Optics wave amplitude question

    In quantum optics, I've been looking at how one can show electromagnetic field is equivalent to a harmonic oscillator. They give the E field as, in one dimension: E_x (x,t) = A . cos(wt) . sin(kz) where the symbols have their usual meanings. A is given as SQRT[2w^2 / Ve]...
  24. SamRoss

    Energy proportional to Amplitude squared?

    Does anyone know a simple derivation that explains why the energy of a wave is proportional to the amplitude squared?
  25. M

    FM Modulation: Solving Problems with 400KHz and 40 Amplitude

    Hello, So I was studying for my exam and came across this exercice we did in class and which I really don't know how we got the answer. It says that if we have a FM with a carrier frequency of 4MHz, and the bandwidth is 400KHz, what is then the maximum deviation.. The answer is 200KHz...
  26. P

    Amplitude and period harmonic motion

    Homework Statement Im confused about what exactly is the period and amplitude of a spring... Is the period -during ocillation-from top to bottom back to top? or vice versa. and is the amplitude 1/4 of the period? Homework Equations The Attempt at a Solution
  27. 3

    What is the Spring Amplitude Problem?

    Homework Statement A block on a spring if pulled to the right and released at t=0s. It passes x=3.00 cm at t=0.685s, and it passes x=-3.00 at t=0.886s. a. what is the angular frequency? b. what is the amplitude? Homework Equations w = 2pi / T w= sqrt k/m The Attempt at a...
  28. T

    Finding amplitude of SHM with a theta vs time graph

    1. What is the amplitude of the pendulum's motion, in meters? (see attached graph) Given: angular frequency=1.26rad/s 2. T=2pi(L/g)^.5; a=-w^2(x); s(t)=Acos(wt+phase); theta=s/L 3. I almost don't even know how to start.. The confusing part I believe is the graph. The max angle...
  29. A

    How Do I Calculate the Modulation Percentage for an AM Waveform?

    Hello everybody! I have a question on amplitude modulation. Homework Statement I'm given an input signal m(t)=0.2sin(1000*Pi*t)+0.5cos(\sqrt{2}*1000*Pi*t) and I'm asked to sketch the AM waveform and to find the modulation percentage.Homework Equations The Attempt at a Solution I'm asking for...
  30. J

    Finding Pitch Circle & Teeth for Amplitude Movement

    How would I work out the pitch circle and number of teeth required to move the mechanism a certain amplitude? Looked over 4-5 sources for pitch circle, but cannot make sense of it..
  31. G

    Calculating Wave Amplitude: A Simple Guide for Frequency and Wavelength

    Hi, does anyone know how to calculate the amplitude of a wave knowing the frequency and wavelength
  32. M

    Amplitude and period of a spring

    Homework Statement A 340 g mass is attached to a vertical spring and lowered slowly until it rests at a new equilibrium position, which is 30 cm below the spring's original equilibrium. The spring is then set into simple harmonic motion. What is the period of the motion? Homework...
  33. S

    Calculating Electric Field Amplitude of Transmitted Light

    Homework Statement A beam of unpolarized light with intensity 30 watts/m^2 passes through a polarizing sheet. What is the electric field amplitude of the transmitted beam? Homework Equations Ia=Ipcos2\Theta Ea=Epcos\Theta Ip=Io/2 The Attempt at a Solution I solved the first...
  34. X

    Tidal amplitude on a molten earth?

    If the lithosphere were suddenly removed, would the earthtide amplitude of the mantle be larger than the .25m or so now measured for the lithosphere?
  35. S

    Amplitude in plane x=y from two speakers placed on x and y axes.

    Homework Statement Two speakers at (x,y,z)=-L,0,0 and (x,y,z)=(0,-L,0) Find the amplitude at all positions in the plane x=y Homework Equations The waves are given by: \tilde{f}_x(\overline{r},t)=\frac{A}{r_x} e^{i(kr_x-\omega t)} \tilde{f}_y(\overline{r},t)=\frac{A}{r_y}...
  36. T

    Amplitude will change after unpolarised wave passes through a polariod

    Can i know whether the amplitude will change after unpolarised wave passes through a polariod?
  37. T

    The probability as an absolut value of the square of the amplitude

    All right, I don't have a problme with the concept, just a specific question. Is the absolute value of the amplitude abs(r^2 + (xi)^2) or abs(r^2) + abs((xi)^2) Or, to put it in a simpler way - Do you absolute the value of the square of the imaginary part? The difference would be, say...
  38. A

    Probability amplitude in Heisenberg e Schrodinger pictures

    Hi, this is my question: suppose that at time t' our system is in the state | \psi(t')\rangle The probability for the system to be in the state | \phi\rangle at the time t'' is the norm of \langle \phi| \psi(t'')\rangle This in the Schrodinger picture. But how i can write the same thing in...
  39. B

    Is it all TIME, and not amplitude?

    I'm just coming to terms with the simple ideas of QED, and I was wondering that if based on these ideas of amplitudes, and let's talk simply (please) about the hands of the stopwatch turning... Can we conclude from that there is some sort of time programmed into all subatomic particles? I mean...
  40. R

    In michelson interferometer, does amplitude of of two waves is

    in michelson interferometer, does amplitude of of two waves is divided. i mean one wave say from fixed mirror has amplitue say A and the wave from moving mirror has amplitude say 0.8A? can we call this coherent source?
  41. P

    Amplitude Entrainment: Forum Q&A

    I am so happy to have found this forum. I am trying to understand a concept about frequency entrainment. I remember reading many times that two different, but similar vibrating bodies can lock into a constructive interference regarding their frequencies, however I thought that their amplitudes...
  42. A

    Intensity of light vs amplitude

    Hi all, It is common knowledge that unpolarized light, when passing through an ideal polarizer, suffers a drop of half its original intensity. But since intensity is proportional to square of the amplitude, can we then infer to say that the new amplitude of light through the polarizer is...
  43. R

    Intensity & Amplitude of Gaussian Beam

    Can tell me the exact relationship between the intensity and the amplitude for a gaussian beam ? I know that I is proportional to |A|2 .. but i want the value of this proportianality constant
  44. R

    Yukawa force versus scattering amplitude

    When does the Yukawa potential apply and when does the scattering matrix apply? Take QED for example. When calculating a scattering amplitude, you have an expansion in powers of the fine structure constant, 1/137. Where does Coulomb's law F=e^2/r^2 come in? As far as I can tell, all...
  45. S

    What is the Amplitude of a Particle? Understanding Photon Waves and Displacement

    If a photon can be graphically demonstrated as a wave with amplitude x, what does the amplitude correspond to on a particle? Is it, it's displacement from its mean position at a given time?
  46. C

    Amplitude of the velocity gradient

    Dear all, Someone could help me to understand how is mathermatically expressed the amplitude of the velocity gradient? For example if vector of velocity is V(Ux,Vy,Wz) The amplitude of the velocity gradient is? : grad(V)= d/dx(Ux) +d/dy(Uy) + d/dz(Uz) Is it fine? Thanks in...
  47. U

    Answering MCQs on Sound Amplitude and Intensity

    Homework Statement Hi All, I have two MCQ, I could not answer them. All choices seem to be close to each others. I would be so grateful if you could help me. When the compression and expansion is very rapid, the sound is said to be high in: a) amplitude b) pitch c) frequency d)...
  48. R

    How Can Bats Detect Ultrasonic Sound Waves at Extremely Low Intensities?

    Homework Statement A bat can detect ultrasonic sound waves with an intensity as low as 1 × 10–13 Wm–2. An ultrasonic source emits sounds waves with a frequency of 54.0 kHz and a power of 1 × 10–7 W. Take the speed of (ultra)sound in air as 340 ms–1 and the density of air to be 1.2 kg/m3...
  49. D

    Understanding Amplitudes for Photon Speed in Feynman's QED

    Im trying to make my way through Feynman's "QED: Strange theory of light and matter". On page 89 he says: How should I understand this ? Is he referring strictly to the speed of light "C" not "c" in a specific medium , in a transparent medium ? I am kinda puzzled by amplitudes greater than c.
  50. B

    What is the relationship between Wavelength(λ) and Amplitude?

    Homework Statement What is the relationship between Wavelength(λ) and Amplitude?Homework Equations V = fλThe Attempt at a Solution Well, i know an increase in frequency will cause a higher pitch, but what happens when the wavelengths increase of decrease?
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