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. gsmtiger18

    Calculating Electric and Magnetic Field amplitude

    Homework Statement A circular uniform laser beam has a power of P = 3.2 mW and a diameter of d = 8.5 mm. The beam is a form of electromagnetic raditation with both electric and magnetic field components. (a) Calculate the intensity of the beam in units of W/m^2 (b) Calculate the energy (delta...
  2. F

    Why does loudness of sound vary as square of amplitude?

    Why does loudness of sound vary as square of amplitude? Why not cube of amplitude or just amplitude?
  3. mmusiak

    B What is the amplitude of a gravitational wave at the source?

    In the most recent postings on LIGO, it is stated that the amplitude of the signal is less than the diameter of a proton after the propagation of the wave over billions of light years. I am assuming that the wave amplitude will decay as 1/r^2, but perhaps that is an incorrect assumption. So is...
  4. Geek007

    A Average amplitude of signal is zero, why?

    hi there, Why does we need to have a signal which always has the average amplitude of zero. i read some where that it would be inefficient for over transmission medium to carry a signal which have amplitude great than zero. Why?
  5. Divinite

    Find the third harmonic (Sound Physics)

    Question: The frequencies of the first three harmonics of a 300 Hz square wave are 300 Hz, 900 Hz, and 1500 Hz. If the amplitude of the fundamental is 1.00 A, then the amplitudes of the second harmonic is _____ A, and the amplitude of the third harmonic is _____ A. I found the answer to the...
  6. vetgirl1990

    Finding amplitude from simple harmonic equation function

    Homework Statement The periodic motion is given in the form: f(t) = Acos(wt+φ) What is the amplitude and phase constant for the harmonic oscillator when: (a) f(t) represents position function x(t) (b) f(t) represents velocity function v(t) (c) f(t) represents acceleration function a(t)...
  7. Rumplestiltskin

    What is the Intensity of Light 12m from a Bulb Shining in All Directions?

    Homework Statement The light from a bulb shines equally in all directions. If 20W of light is given off, what will the intensity be 12m from the lamp to 2 significant figures? (Consider the shape of the region illuminated if the light hits this surface after traveling 12m in all directions.)...
  8. J

    Amplitude at the point of interference

    Homework Statement [/B] Consider 2 radio antennas placed on a 2 dimensional grid at points x1 = (300,0) and x2 = (-300, 0). If the antennas are out of phase such that ϕ2-ϕ1 = π/4 and both are emitting waves of frequency 2.59 MHz. What will the amplitude of the resultant wave be at the point...
  9. D

    Probability and probability amplitude.

    Quoted from reddit, an explanation for quantum superposition : By analogy, you could say that the traveling electron is in a superposition of paths. Some are direct (close to what is called the "classical path" -- the path that a particle would take according to classical mechanics). Some are...
  10. M

    Stationary waves - why same amplitude etc?

    Homework Statement Hi, In my textbook, it says that waves superposing to form stationary waves, in addition to being in opposite directions, should have the same frequency and ideally the same amplitude - why the 'ideally' and why is having the same amplitude important? Is it because then we...
  11. S

    Propagation amplitude and time-evolution operator

    I know that the time-evolution operator in quantum mechanics is ##e^{-iHt}##. Is this also called the Schrodinger time-evolution operator? Also, can you guys explain why the amplitude ##U(x_{a},x_{b};T)## for a particle to travel from one point ##(x_{a})## to another ##(x_{b})## in a given...
  12. M

    Amplitude and Young double slit experiment

    Homework Statement For a question in a worksheet (the actual question is irrelevant), my physics teacher said, in the context of the Young double slit experiment with light, if you make one of the slits smaller, then the amplitude of light from that source will also decrease. Is that true...
  13. L

    Amplitude of damped mass-spring system

    Homework Statement Given the IVP \ddot{r}+\dot{r}+20r=0\\ r(0) = 0.8\\ \dot{r}(0) = 0 for the length of an oscillating spring (damped), we find that the general solution is r=e^{-0.5t}[0.8\cos(\sqrt{19.75}t)+\frac{0.4}{\sqrt{19.75}}\sin(\sqrt{19.75}t)] and I wish to find the curve bounding...
  14. P

    How to Calculate Amplitude Modulation Index Without Prefix

    Homework Statement Let's say we have a carrier signal xc(t) = AcCos(ωct) And there is a modulating signal or we can call it the information signal xm(t) = Am Cos(ωmt) and the modulation index is given as 0.8 How to write the modulated signal? It's really confusing as many people give different...
  15. Z

    The definition of transverse amplitude in the process: ep→epπ

    When CLAS of Jlab describe the result of the process ep→epπ,the use the terminal "transverse amplitude" Ml±(W,Q2), El±(W,Q2),and "scalar(longitudinal) amplitudes"Sl±(W,Q2),they correspond to photons of the magnetic, electric, and Coulombic type.Are they observables? The index of...
  16. K

    Negative amplitude of cross-correlation function in ICCS?

    I am an undergrad working in biophysics research, and I was hoping you guys may have input on a simple but strange problem I'm facing. I don't know if this is appropriate for this forum, but it is not an especially specialized or complex problem and I am desperate. I am currently conducting...
  17. B

    Amplitude vs Location when KE=PE?

    Homework Statement A 0.50-kg object is attached to an ideal massless spring of spring constant 20 N/m along a horizontal, frictionless surface. The object oscillates in simple harmonic motion and has a speed of 1.5 m/s at the equilibrium position. (a) What is the amplitude of vibration? (b) At...
  18. B

    Amplitude and Period of Oscillation from Collision

    Homework Statement A 2.00-kg object is attached to an ideal massless horizontal spring of spring constant 100.0 N/m and is at rest on a frictionless horizontal table. The spring is aligned along the x-axis and is fixed to a peg in the table. Suddenly this mass is struck by another 2.00-kg...
  19. N

    Can you measure the amplitude of a specific light wave?

    Hello world, I'm currently in my last year of high school and only just getting interested into quantum physics, still learning new things every day. I was wondering if there's a way to measure the specific amplitude of a light wave(Or electromagnetic wave) and what this says about the wave...
  20. M

    Transmission and Reflection Amplitude for Delta Potential SE

    This is not a homework question per se, but it's a simple enough computation question from some notes I'm reading that I think it belongs in this section. I will do my best to keep to you guys' formatThis is not a homework question per se, but it's a simple enough computation question from some...
  21. A

    Simple harmonic motion: mass on a spring is hit by a bullet

    Homework Statement A 4.0kg block is suspended from a spring with force constant of 500N/m. A 50g bullet is fired into the block from directly below with a speed of 150m/s and is imbedded in the block. Find the amplitude of the resulting simple harmonic motion. Homework Equations F=-kx...
  22. H

    Using Feynman rules to calculate amplitude

    Given a diagram, how is one supposed to apply the feynman rules to calculate the feynman amplitude?
  23. E

    Opamp oscillator with amplitude stabilization

    It is known R4=R5=1.2k. My task is to calculate amplitude of oscillations at v0: Opamps and diodes are ideal. I did analysis of circuit without amplitude stabilization and I got oscillation frequency, but I can't figure out how diodes stabilize amplitude in this circuit. Any sugestion...
  24. M

    Amplitude of a process + interference term, how what?

    Hello guys, Suppose a process 1+2--->3+4 proceeds thru 3 different intermediate particles and has 3 Feynman diagrams. When we compute the probability then what does the cross terms( interference ) mean? and do we have to always compute the cross terms? What I mean is that when you have 3...
  25. B

    Neutrino-neutrino to WW amplitude via Z-exchange

    Homework Statement I am working through an example in Chapter 6 of Quigg's Gauge Theories. I have it mostly figured out, with the exception of how to work out the S^{\mu}S^{\nu} term. All he writes is "...the term is impotent between massless spinors." Homework Equations I begin with: What...
  26. K

    Oscillation amplitudeWhat is the amplitude of the oscillation?

    Homework Statement A 1.4-kg cart is attached to a horizontal spring for which the spring constant is 60 N/m . The system is set in motion when the cart is 0.27m from its equilibrium position, and the initial velocity is 2.6 m/s directed away from the equilibrium position. A. What is the...
  27. K

    What is an approximate amplitude of a phonon?

    I am aware that phonons are lattice vibrations - and that the amplitude of vibration would depend on the temperature. But say, at room temperature what would the order of magnitude of these lattice vibrations be ? In particular, in continuum limit these phonons can be treated as elastic...
  28. G

    Calculating Tree Amplitude for Spin J Exchange

    I am wondering something about the tree amplitude for exchange of a spin J resonance-- the basic calculation that exhibits the famous regge behavior. I see that one way to do the calculation is simply to note that the 4-point function for spin J exchange amongst massless particles arises from an...
  29. R

    Amplitude and Vibrations in Springs

    Homework Statement The amplitude of vibration of a mass on a horizontal spring experiencing SHM is = 0.13m. The mass is 85g and the force constant is 55N/m. a) What is the maximum elastic potential energy of the system. b) Find the speed of the mass when it's position is x = 7.4cm from the...
  30. onion3000

    Help with understanding modulation in AM, FM and PM radio

    I have a few questions about AM, FM and PM. 1. If FM (or PM) radio modifies the frequency of the signal, how is the signal picked up without having to change the frequency constantly? 2. If PM modulates phase, which modulates frequency, what is the difference between PM and FM? 3. Why is AM...
  31. S

    Light waves with 0 amplitude due to extreme red shift?

    Is it theoretically/mathematically possible for light waves to be red-shifted so much that it's amplitude is equal to zero?
  32. Toon

    Superposition: Adding two waves together -- amplitude help

    Homework Statement " Two traveling waves are generated on the same taut string. Individually, the two traveling waves can be described by the following two equations: If both of the above traveling waves exist on the string at the same time, what is the maximum positive displacement that a...
  33. DoobleD

    Dipole EM wave field lines VS decreasing amplitude

    The E and B field lines of a dipole radiating EM waves looks like that (sorry for the poor quality) : What I wonder is how can we see that the amplitude of the fields decrease as 1 / r? When you look as such a picture it actually feels likes the amplitude should rises. The E field gets...
  34. lfqm

    Fixed amplitude of electric field operator in quantum optics

    Hi guys, I'm trying to understand why does the amplitude of the electric field operator in a cavity is fixed at \left ( \displaystyle\frac{\hbar\omega}{\epsilon_{0}V} \right )^\frac{1}{2} Every book I read says it is a normalization factor... but, normalizing an operator?, what is the meaning...
  35. T

    Probability Amplitude Homework: Showing Definition of Time Derivative

    Homework Statement Show, using the definition, that ##\frac{d}{dt}\langle \emptyset(t)|\psi(t)\rangle=\langle \frac{d}{dt}\emptyset(t)|\psi(t)\rangle+\langle \emptyset(t)|\frac{d}{dt}\psi(t)\rangle## Homework EquationsThe Attempt at a Solution I'm looking at this and I have no idea where to...
  36. CupOfAppleTea

    Intro Physics Books on Phase and Amplitude of a sine wave

    Hi! I am searching for litterature on the decomposition of a sine wave in its three parameters: phase, frequency and amplitude. I just need it to justify an analysis that I am doing this way and it appears to be hard to find such a book. I find many website but nothing I can cite seriously! Thanks!
  37. S

    Photon Displacement in EM Waves (Amplitude)

    I am curious on what is meant by amplitude in an EM wave. From all the searching I have done the amplitude has something to do with the density of photons in the EM wave, and the frequency with energy of the photons. The part I am confused about is the fact that the wave is oscillating. I...
  38. H

    Transmission and Reflection amplitude

    To calculate Transmission and Reflection amplitudes (t and r), say in the figure below which is composed of three regions, first we have the solution of Schrodinger equation in each region as: \psi _i=A_i |i> +B_i |-i> ; i=I,II,III. It seems that by matching the three wave functions and their...
  39. I

    Amplitude modulation and amplifier efficiency

    " A intelligence signal is amplified by a 80% efficient amplifier before being combined with a 12kW carrier to generate the AM signal. if it is desired to operate at 100% modulation, what is the DC input power at the modulator" The choices are a: 12kW b. 7.14kW c.7.5kW d. 15kW my solution...
  40. E

    Difference between X and Amplitude (Simple Harmonic Motion)?

    V=Vo √1-(x^2/a^2) X is the distance of the spring's stretch, but how would you rearrange the equation if you are looking for Amplitude? They both use the same units (meters) as far as I am concerned. Help would be appreciated, thanks; I am still a beginner with Physics.
  41. adi adi

    Finding amplitude from superposition

    Homework Statement so there is this problem : find the amplitude from the superposition of Z1 and Z2 where Z1 : 8 sin 100t, A1= 8m and Z2 : 6 sin (100t-pi/2), A2=6m Homework Equations i know that all we need to do is add them and do the trig using sine additon, but i couldn't do that because...
  42. K

    Scattering amplitude, link between quantum mechanics and QFT

    In quantum mechanics, we can define the scattering amplitude f_k(\theta) for two particles as the coefficients of an outgoing spherical wave. More precisely, the asymptotic behaviour (when r\rightarrow\infty) of a wave function of two scattering particles, interacting with some short range...
  43. goonking

    Spring Amplitude Calculation: Solving for the Amplitude Given Initial Conditions

    Homework Statement Lets say I have a spring, resting at a length x at t = 0 seconds, with a spring constant k, and at the end is attached with a block with mass m. I give the block a velocity v in the -x direction. Now I'm asked to find the Amplitude. Homework EquationsThe Attempt at a...
  44. Alex_Neof

    Amplitude of velocity (Travelling wave)

    Homework Statement A wave traveling along a long string has the form: ##y(x,t) = 20sin(3x - 2t), ## where ##x## is in metres and ##t## is in seconds. Find the amplitude of the velocity of any particle of the string. 2. Homework Equations Do I just find ##\frac {\partial y}{\partial t}...
  45. A

    AH physics exam tomorrow - help with waves question? thanks

    1. Homework Statement If the optical path diff between two light waves is lambda/2 will they always interfere destructively? if this in true then wherever one wave undergoes aphase change of pi at one surface and the second wave does not then these two will always interfere destructively...
  46. D

    Pendulum Damping force effect on amplitude over time

    I am struggling with setting up a problem to solve for the change in amplitude of a pendulum affected by a damping force (presumable air friction) over a time period. The original amplitude of the pendulum is 1.4 m from the equilibrium on a 15 m massless wire with a 110 kg brass bob at the end...
  47. G

    Calculate amplitude and phase of a filter cricuit

    I have the values for all the voltages and currents. I'm wondering how I go about it, given that v3 = v30 (cos (Θ3) + isin(Θ3)) and I have a value for v3. Since v3 = i4 * Z where Z is C3 and R2 in parallel, there'd still be 2 unknowns. I feel as though I'm missing something obvious, if anyone...
  48. O

    Amplitude and Velocity of Component Waves

    Homework Statement A string vibrates according to the equation y(x,t) = 2.0*sin (0.16x)cos (750t) , where x and y are in centimeters and t is in seconds. (a) What are the amplitude and velocity of the component waves whose superposition give rise to this vibration? (b) What is the distance...
  49. O

    Find the amplitude of the resulting simple harmonic motions

    Homework Statement An 8.0 lb block is suspended from a spring with a force constant of 3.0 lb/ in. A bullet weighing 0.10 lb is fired into the block from below with a speed of 500 ft/sec and comes to rest in the block. a) Find the amplitude of the resulting simple harmonic motions b) What...
  50. F

    Amplitude of two carts attached by a spring

    Homework Statement #1. [Coupled Oscillators] A cart of mass m (car #1) and another cart of mass 2m (car #2) on a horizontal surface are connected by an ideal massless spring of spring constant k. The two carts are set into oscillation about their center-of-mass (CM) in Simple Harmonic...
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