What is Amplitude: Definition and 867 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. 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...
  2. J

    Phase shift and amplitude change when put through FIR filter

    Hey all, I am having trouble with this problem: A sampled sinusoidal signal having a normalized frequency of 0.30π is sent through an FIR filter. The filter impulse response is, h[n] = 1/3δ[n] + 1/3δ[n-1] + 1/3δ[n-2] From this I must find out by what factor the input signal is...
  3. T

    Find Magnetic Field Amplitude from EM Wave Amplitude

    Homework Statement A plane electromagnetic wave propagating in free space has an amplitude (\sqrt{3}/2)a_{y}-(1/2)a_{z} V/m. Find the amplitude of the accompanying magnetic field assuiming the frequency of the electric field is 1 GHz. Homework Equations f_{E} = f_{H}...
  4. J

    Find Amplitude and Equilibrium in Simple Harmonic Motion

    Homework Statement A 0.241-kg particle undergoes simple harmonic motion along the horizontal x-axis between the points x1 = -0.349 m and x2 = 0.419 m. The period of oscillation is 0.511 s. Find the frequency, f, the equilibrium position, xeq, the amplitude, A. Homework Equations The...
  5. C

    Calculating amplitude of pendulum

    Homework Statement In a science museum, a 100kg brass pendulum bob swings at the end of a 13.0m -long wire. The pendulum is started at exactly 8:00 a.m. every morning by pulling it 1.7m to the side and releasing it. Because of its compact shape and smooth surface, the pendulum's damping...
  6. F

    Variable amplitude for shaker table

    Hi All, I built this shaker table: and I am now trying to change the amplitude so that it is no longer fixed but instead variable. The frequency I can change but the amplitude is fixed given this design. Does anyone have any suggestions on how to be able to change the amplitude so I can...
  7. T

    Group/Phase velocity - amplitude, frequency, velocity

    Homework Statement I've been working on a python simulation program that is based on phase velocity and group velocity. It looks like the following screenshot, where three parameters (E02, f2, and v2) can be adjusted. These three parameters are adjusted in terms of E01, f1, and v1. I...
  8. R

    Why Is Instantaneous Value Used in Amplitude Modulation?

    In the amplitude modulation equation, V=(Ec+Ei*coswt)coswt I don't understand why the instantaneous value of information signal is used. Shouldnt it be peak value as that would give the maximum value (amplitude)?
  9. J

    Photon Amplitude: Is It Right or Wrong?

    Does it make sense to talk about the amplitude of a photon? In my mind, the amplitude of the photon is the maximum strength that the electric and magnetic field gets as they oscillate. If you were to change the amplitude of a photon (say increase), then the maximum strength of the e&m fields...
  10. R

    Scattering Amplitude for Many Particles (Born Approximation)

    Homework Statement Given that the scattering amplitude off of a single atom is f_{1}(\vec{q}), find the scattering amplitude for 1) four atoms each placed in the corner of a square of length a, and 2) two atoms a distance d apart Homework Equations The total scattering amplitude can...
  11. H

    Amplitude of harmonics higher than fundamental frequency

    Dears, I have an vacuum pump creating the vacuum approximately 10^-8 mbar. The rotor consists blades and it's placed in bearings. One side is ceramic bearing and the other one is maglev type(magnetic). I measure noise and vibrations of the pump. Significant peak of both units is naturally at...
  12. T

    Harmonic oscillator superposition amplitude evaluation

    Hi all Homework Statement I have the first three states of the harmonic oscillator, and I need to know the amplitudes for the states after the potential is dropped.Homework Equations u_{0}=(\frac{1}{\pi a^{2}})^{\frac{1}{4}} e^{{\frac{-x^2}{2a^2}}} u_{1}=(\frac{4}{\pi})^{\frac{1}{4}}...
  13. L

    Use Fourier analysis to construct an amplitude spectrum

    Homework Statement A sensor yields a signal y(t) = |sin(120\pit)| a. Using Fourier analysis please construct an amplitude spectrum for this signal. Homework Equations A0 = \frac{1}{T}\int ^{-T/2}_{T/2}y(t) dt An =\frac{2}{T}\int^{-T/2}_{T/2}y(t)cos\frac{2n\pi t}{T}dt The Attempt at...
  14. V

    How to find the phase shift and amplitude ratio

    i am looking for the amplitude ratio and phase shift of this graph? could someone explain me how to obtain these results from this type of graph? thank you
  15. S

    Calculating Amplitude in Simple Harmonic Motion

    Hello and thanks for you time. Just a quicky :-) For a free vibration impulse response, the acceleration a is given by: a = -ω^2*Asin(ωt) So am I right in saying that you can rearrnage to calculate the amplitude A as: A = a/(-ω^2*sin(ωt)) Thanks, Steve
  16. S

    Amplitude in a simple pendulum - angle or distance?

    Is amplitude in a simple pendulum measured as an angle, theta, or as a distance? If it is an angle, is it in radians or degrees. Also, what is the equation? How does amplitude relate to x=Acos(ωt)?
  17. O

    Amplitude of all electromagnetic wave are same ?

    Gamma ray can use to kill tumour because of higher frequency and therefore higher energy. The energy here is the number of time of the wave hit on the tumor or the amplitude of wave ? Thank you.
  18. J

    Diffraction and Probability Amplitude

    Hi, I would like to understand how diffraction works in layman's terms. Why does a wave entering a corner or a slit (in the case of light) bend? I found an answer here, but it doesn't make a lick of sense. http://wiki.answers.com/Q/How_does_diffraction_work What is a probability...
  19. R

    Find wavelength, Phase Difference, and amplitude from min and max

    Homework Statement See attached image Homework Equations Δphi = 2pi(Δx/λ) + Δphi0 = 2pi(m) -- at the maximum Δphi = (m + .5) (2pi) -- at the minimum The Attempt at a Solution The first step should be to solve for lambda, the wavelength. So I plug in the knowns: At 30 cm...
  20. L

    Calculate scattering amplitude by delta function potential

    Homework Statement I need to give scattering amplitude f(θ) in Born approximation to the first order in the case of delta function scattering potential δ(r). The problem is in spherical coordinate and I'll give major equation concerned.Homework Equations The equation for scattering amplitude is...
  21. M

    Probability amplitude versus probability distribution

    Homework Statement The question is "Comment on the physical consequence of two probability distributions being equal to each other even though the probability amplitudes are not the same." Homework Equations The Attempt at a Solution I understand that the modulus squared of the...
  22. heycoa

    Optics | Amplitude of Electric Field Given Radiant Flux Density

    Homework Statement A laser provides pulses of EM radiation in vacuum lasting 7.47* 10-12 s. If the radiant flux density is 2.65 * 1020 W/m2, determine the amplitude of the electric field (x *1011) of the beam. Units are required as listed in instructions. Homework Equations Irradiance =...
  23. PhizKid

    Finding amplitude of oscillation with only k, x, v, and a

    Homework Statement An oscillating system of a block attached to a string where k = 400 at some time t has a position x of 0.1 m, velocity of -13.6 m/s, and accel. of -123 m/s^2. Find the amplitude of the motion. Do not use energy. Homework Equations x = Acos(wt + phi) v = -Awsin(wt +...
  24. A

    Optics: Finding the wave equation given position and amplitude information

    A harmonic wave traveling in +x-direction has, at t = 0, a displacement of 13 units at x = 0 and a displacement of -7.5 units at x = 3λ/4. Write the equation for the wave at t = 0. Homework Equations The equation for a harmonic wave is r = asin(kx-vt+θ) a being the amplitude k...
  25. M

    Amplitude Change in Oscillations with Varying Spring Constants

    Homework Statement A mass is attached to the wall by a spring of constant k. When the spring is at its natural length, the mass is given a certain initial velocity, resulting in oscillations of amplitude A. If the spring is replaced by a spring of constant 2k, and the mass is given the same...
  26. A

    Hooke's Law: How to find Amplitude

    Hello all, (Newbie here so I hope I'm posting this in the right section, if not please guide me to the correct one) I'm studying Hooke's Law in Physics and there is something I can't understand. The equation for the Simple Harmonic Motion of a spring is given by x'' + wx =0 the general...
  27. R

    Find Frequency and Amplitude from Max Velocity and Accn

    Homework Statement See attached screenshot Homework Equations Vmax=Aω ay=-ω2A The Attempt at a Solution The given max velocity is 1.2 m/s, so 1.2 = ωA Ay = -ω^2A 1.2/A = -√260/A A = 0.005
  28. Nono713

    Fresnel amplitude coefficients for unpolarized light

    Hi, I have an issue with the Fresnel amplitude coefficients. I know they are given in two versions, for s-polarization and p-polarization. A version for unpolarized (randomly polarized) light is available for the power coefficients - it's just an average - but I could not find such an expression...
  29. A

    Wave: amplitude, frequency, wavelength

    Homework Statement Original question: A boy flicked a string harder, describe the changes of the waveform and the speed of the wave. Homework Equations V = f x λ Frequency is how many completed oscillation per second. Wavelength is distance between two adjacent points of the same...
  30. A

    Scattering amplitude of diffracted beam by a crystal

    Homework Statement The scattering amplidtude, F, of a, by a crystal, diffracted beam is defined to be: (1) F=\sum{_\vec{G}}\int n_{\vec{G}}e^{i(\vec{G}-\delta\vec{k})\cdot \vec{r}}\mathrm{d}V The integral is over all the volumeelements, dV, of the crystal. n_{\vec{G}} is the local...
  31. C

    Power in beam of light given amplitude

    I would like to calculate the power of a beam of light once I know the electric field amplitude. For example if I know the amplitude along a line from -1 meter to +1 meter every 0.5 m is [1, 2, 2.5, 2, 1 V/m], how can I find the power from this is? Is there enough info? (it's in vacuum/air)...
  32. J

    Calculate Differential Cross Section, Amplitude from Lagrangian

    Lagrangian I have is little bit massy so I don't write in here. Like in ψψ(dagger) , or ψ∅ -> ψ∅, How can I calculate the differential cross section or total, or amplitudes?
  33. R

    Are these three things DEPENDENT on Amplitude?

    So if Period is the only thing that isn't dependent on amplitude, then that must mean Energy (PE = 1/2 k A2), maximum acceleration, and speed is dependent on amplitude?
  34. R

    How do you find the force extended if given the amplitude? Forced Oscillations

    How do you find the force extended if given the amplitude? Is main questions, I also have one slight question. Ok, doing a problem. There is no damping. A (.15kg) object is hanging from a light(6.30N/m) spring. A sinusoidal force with an amp of 1.7 N drives the system. And the problem is...
  35. H

    Why Does Transition Amplitude Not Equate to Time Evolution in Quantum Mechanics?

    I cannot see why the probaability ampltiude for an initial state to turn into another state is the inner product between the "another state" and the propogator acting on the initial state, since this is just equivalent to the inner product between the "another state" and the evolved initial...
  36. G

    Does logarithmic decrement depend on initial amplitude?

    Lets say we have a weight attached to a spring. When releasing it under water (whole motion occours under water) at different initial amplitudes, will logarithmic decrement be the same? And will the period change? I think it should be the same for different initial amplitudes. But...
  37. S

    Scattering Amplitude for a given potential

    Hello again, My question is on determining the scattering amplitude via time-dependent perturbation theory (first-order) for a given potential - I believe the perturbation potential is modeled due to some interaction between two scalar particles and has form: \delta V=\lambda...
  38. A

    Question on the relationship between intensity of sound, amplitude and 1/r^2

    Homework Statement Suppose sound wave is emitted uniformly in all directions by a speaker. At a distance of 1.1m, the amplitude of it sound is 1.2x10^-8m What is the amplitude of sound at a distance of 1.7m?The Attempt at a Solution What I'm confused is why does the amplitude of sound change...
  39. L

    What is the output voltage amplitude from the amplifier in the given circuit?

    The circuit in the figure is driven by a 9 mV amplitude signal generator with an output impedance of 2 kΩ. What is the output voltage amplitude from the amplifier? So what I did basically is use the formula Vout = -R2/R1 x Vin So.. I know Vin is 0.9 V (9mv) and R2 = 12 R1 = 1 that...
  40. J

    Amplitude of an electromagnetic wave

    Lets take visible light for example. The frequency/wavelength determines the amount of energy and the type of wave(micro,radio,gamma ect.) The intensity or brightness is determined by the amount of photons. So what does the amplitude determine?
  41. B

    Amplitude of Two Waves in Interference

    In my textbook, when two waves of the form: y_1 = A\cos \left( 2\pi f_1t \right) y_2 = A\cos \left( 2\pi f_2t \right) combine, the following trig identity is used: \cos a + \cos b = 2\cos \left( \dfrac{a-b}{2} \right) \cos \left( \dfrac{a+b}{2} \right) which yields an expression for y...
  42. T

    Scattering Amplitude of Atomic Charge Spread as Wavefunction

    Determine scattering amplitude for atomic charge which is "spread" as wavefunction Homework Statement Derive the scattering amplitude and differential cross section for Rutherford scattering (done this). Now rederive the same quantities for the atomic charge which is "spread" with the...
  43. A

    Linear equations for amplitude factors

    My book discusses the oscillations of systems for small pertubations around an equilibrium point. By considering taylors expansions of the potential and kinetic energy they are led to a set of equations for the amplitude factors. I have attached the crucial lines as a picture. My question is...
  44. M

    Intensity of different color light & its relation to energy AND Amplitude

    Hi Let's stick to the classical limit. We have 2 monochromatic light waves of same intensity. Let's say one is blue and one is red. Now this means the individual photons of the blue light have more energy(obviously, higher frequency) and the red light photons have lower energy. But since...
  45. H

    Calculating Amplitude of Transverse Wave

    Homework Statement The wavefunction of a transverse sinusoidal wave on a string has the form y(x,t) = Acos(kx + ωt + φ), where x and y are in m, t is in seconds and φ is the phase constant in radians. The wave has a period T = 24.5 ms and travels in the negative x direction with a speed of...
  46. A

    Why does a capacitor decrease current amplitude

    Suppose you run an AC-current through an RC-circuit. Writing it all up in terms of the complex impedance you find that the current amplitude is decreased due to the capacitor. Physically I do not understand this. How does a capacitor decrease the amplitude of the current, when the current is...
  47. R

    How to draw a Amplitude and Phase spectrum

    The problem statement Sketch the Amp spectrum of the following... Additionally, for x3, sketch the phase spectrum... ( j is the imaginary number) x1(t) = cos(10pi*t) + cos(3pi*t) x2(t) = cos(10pi*t) + cos(5pi*t) - j*sin(10pi*t) x3(t) = cos(10pi*t + (pi/6)) + j*sin(10pi*t) The...
  48. B

    Simple harmonic motion - Find amplitude given period

    Homework Statement A block rides on a piston that is moving vertically with simple harmonic motion. (a) If the SHM has period 2.65 s, at what amplitude of motion will the block and piston separate? Homework Equations x(t)=xmcos(ωt + ∅) a(t)=-w2xmcos(ωt + ∅) Where xm is the amplitude...
  49. T

    What Is the RMS Amplitude of a Sinusoid in a Noisy Environment?

    Q: A single sinusoidal signal is found in a large amount of noise. If the RMS value of the noise is 0.5 volts and the SNR is 10 dB, what is the RMS amplitude of the sinusoid? I've related the question to the following equation: SNR=20log(singal/noise)dB My answer is 1.58 volts, BUT I'm...
  50. S

    Amplitude modulation frequency component

    Hello Everyone! About Amplitude Modulation, Usually it is seen in the book or web that (e.g. http://www.ni.com/white-paper/3002/en ) '''' The message signal can be represented by m(t) = Mb cos(2πfb + φ) and the carrier signal can be represented by c(t) = Ac cos(2πfc + φ), Now...
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