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. 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...
  2. D

    Calculate the electric field amplitude

    Homework Statement Calculate the average irradiance for the given laser beam. λ=645nm, P=3mW, d=1mm. Homework Equations S=[E X H] S_avg = (1/2) * c * n * ε0 * E0^2 The Attempt at a Solution I understand the Poynting vector and I can derive the average irradiance formula. I...
  3. A

    Interference by amplitude division (double reflection) for wedges

    Homework Statement Transparent wax of refractive index n=1.3 is deposited on top of a glass plate of width 1cm and refractive index n=1.5. The thickness of the wax is 0.01mm at one end of the plate and tapers uniformly to zero at the other end of the plate, which is defined to be at x=0. At...
  4. S

    Spring Stiffness and Amplitude, not understanding

    Hi, For an undamped mass, spring system subject to a harmonic force, the equation is: ma+kx=Fsin(ωt) where a=d^2/dx^2 After solving the diff eqns, the steady state amplitude is: X=(F/m)/(ω^2-ω0^2) where ω is the frequency and ω0 is the natural frequency =sqrt(k/m) according to the...
  5. C

    How does the amplitude on a EM wave graph correspond to the number of photons?

    Hello all! I am trying to understand ER on a more intuitive level. I can see the relationship between energy and frequency. The relationship between amplitude and photon number is less clear. So far I have E = hf. I understand that the intensity of light is a function of the number of...
  6. C

    Energy of incident of light to amplitude of light?

    Homework Statement A sheet of glass transmit 70% of the energy of the incident light What is the value of the quantity: (Amplitude of transmitted light) / (Amplitude of incident light) A:0.49 B:0.70 C:0.84 D:1.19 Homework Equations Intensity is proportional to amplitude square...
  7. S

    Potential Step (wave amplitude)

    1. If the incident wave is coming from LHS, what happens to the wave amplitude on the RHS when electron energy is equal V0? 2. the wavevectors on both sides of the step are different (generally), is there an energy at which the have the same magnitude? thanks for any help..
  8. C

    Natural frequency, damping ratio and steady state amplitude help needed

    (1) A mass of 3.0 kg is suspended from a vertical spring and produces a static deflection of 60 mm. The system is also subjected to viscous damping of 36 N s/m. Calculate the value of the: (a) natural frequency i. In Hz ii. And rad/s (b) damping ratio...
  9. Z

    Bosons's amplitude to go into the same state at low temperatures

    Hi I was reading Feynman's third book and I don't understand why, with bosons at low temperatures, 'there's more amplitude to go into the same state than into an unoccupied state by the famous factor √n, where n is the occupancy of the lowest state'. Thanks.
  10. H

    Obtaining Phase and Amplitude from FFT

    Is it possible to calculate the phase and signal amplitude from data gained from FFT? For instance, if I have a samples from a signal B+A*cos(ψ), is it possible to obtain A and ψ? Extra challenge: is it possible to do so without division? (I am looking to put this on a DSP and division is...
  11. A

    How does amplitude modulation work

    I read on a website that in amplitude modulation the actual carrier wave does not change its amplitude but rather the sidebands. Is this true
  12. S

    Two ideal springs oscillating, find amplitude and phase difference between them

    Hi, I am repeating first year exams and would really appreciate some help with my study. Just can't seem to get my head around this problem. Homework Statement Consider two identical ideal springs with a mass m attached which are harmonically oscillating out of phase relative to each...
  13. W

    MATLAB Calculate amplitude, phase and energy spectrum using FFT in MATLAB

    Hello all, I have a vector, let's say A, which has measured values of the Earth's magnetic field (and if it is relevant, two vectors X and Y with the coordinates of the point each value was measured). I need to calculate the amplitude, phase and energy spectrum using FFT in MATLAB X...
  14. S

    Electric field amplitude of a sphereical wave

    Homework Statement What is the electric field amplitude at a distance of 0.67 m from a 90 W lightbulb? Assume all the power of the bulb goes into light of a single color with lambda = 500 nm and assume the bulb produces a spherical wave. Homework Equations I don't know what equations...
  15. S

    Amplitude of a magnetic field of an electromagnetic wave

    If the intensity of an electromagnetic wave is 80 MW/m^2, what is the amplitude of the magnetic field of this wave? (c = 3.0 x 10^8 m/s, permeability of free space ''miu subzero''= 4π × 10^-7 T ∙ m/A, permittivity of free space ''E subzero'' = 8.85 × 10^-12 C^2/N ∙ m^2) 80MW/m^2= 80,000,000...
  16. J

    Solving Forced Oscillation Amplitude w/o Angular Frequency

    Does changing the angular frequency change the amplitude of a forced oscillation? If so, I don't understand how that can be. I guess that the angular frequency is based only on the springs and dampers? So assuming those are the same then the angular frequency will always be the same? Are...
  17. H

    The Correct Amplitude of a Fourier Transform

    If you take the absolute value of the FFT output, does that give you the amplitude? I am asking because I have seen example where that is taken as the amplitude, and examples were the absolute value is multiplied by either SQRT2 or by 2 to get the magnitude. So my question is what is...
  18. Roodles01

    Amplitude of oscillating magnetic field

    N = 1/2 E0 √(ε/μ) so E0 = √2*N*(ε/μ) where the value of ε/μ is 376.7Ω I have a similar question to this, below, regarding amplitude of an oscillating magnetic field. Yes, I'd like the answer, but am initially stuck deciding whether the mW is milli- or mega- Homework Equations A laser...
  19. D

    Solving Higgs Decay Invariant Averaged Amplitude Problem

    Homework Statement I have decay of Higgs to fermion and antifermion and I need to find out the invariant, averaged amplitude. And I wrote down the Feynman diagram, and calculated everything and I came to this part: \langle|M|^2\rangle=\frac{g_w^2}{4}\frac{m_f^2}{m_w^2}(4p_1\cdot...
  20. J

    Amplitude of equation of motion

    Hello, I have worked out some force diagrams for forced oscillations and ended up with the solution as : mx_double_dot+rx_dot+kx=Pcos(Ωt) I am now asked to work out the amplitude. I know all of the variables except frequency(Ω). What equations can I use to find that? Thanks.
  21. M

    Amplitude-Frequency Relationship in Energy Calculation

    I know in classical physics we calculate the energy based on the Amplitude. I also know we calculate the energy in QM based on Frequency. I know also that it was experimentally deduced that it is the freq. based on the photo electric effect...and so on... What I'm interested is in the...
  22. Y

    Calculate Vibration Amplitude, Frequency Range for Derrick Drilling

    I have a steel drilling Derrick 240 feet high mounted central to a ship, this is used for drilling for oil. Calculations have been done on the Derrick in regards to reaction forces in different modes of operation(drilling, transit etc). I need to do a vibration analysis of different points on...
  23. M

    A body moving with simple harmonic motion has an amplitude of 1

    A body moving with simple harmonic motion has an amplitude of 1 meter and the time for one complete oscillation is 2 seconds . Determine the velocity and acceleration of the body after 0.4 second from the mean position ? this is the answer : Vx = w root(r^2-x^2) ax=w^2.X w= 2Pi/t =...
  24. M

    Complex Amplitude: Physical Meaning & Significance

    I am curious about the complex nature of the amplitudes used in Schrodinger's equation, and what (if anything) it means physically. I ran across this topic being discussed sometime in the past on this forum, and several posters alluded to some deep significance to this fact, but didn't...
  25. C

    Finding amplitude of a baby in cot

    Homework Statement A baby bounces up and down in her crib. Her mass is 10.5 kg, and the crib mattress can be modeled as a light spring with force constant 654 N/m. The baby soon learns to bounce with maximum amplitude and minimum effort by bending her knees at what frequency? b)If she...
  26. C

    Why do you get sideband frequencies for amplitude modulation (AM)?

    I thought that the frequency was constant for AM modulation, and just the amplitude was modulated. So why are there a range of frequency's (side bands around the baseband) when the signal is plotted on a frequency domain graph?
  27. X

    Current element signal amplitude

    Homework Statement A 50cm long vertical current element located on a conducting ground plane radiates a 10MHz signal. 5km away from the element on the ground plane the amplitude of the signal is 0.1millivolts per meter. When the frequency is switched from 10MHz to 5MHz with current amplitude...
  28. T

    Calculating Peak Amplitude of Water Wave Motion

    I have now in some time tried to figure out a way to calculate the peak amplitude of a water wave, after starting the wave motion by dropping an object, with a certain weight from a given height, in the water. I am not in need of the information, but it would be nice to know. I will hope...
  29. Twinflower

    Calculate the amplitude of the fifth harmonic (square wave + HP filter)

    Homework Statement A high pass filter tuned for a corner freq. of 40 000 rad/sek and with a damping coeffisient of 1/sqrt(2) is being subjected to a square wave voltage with amplitide of 1 volt and 8000 rad/sek. What is the amplitude of the fifth harmonic on the output side of the filter...
  30. S

    Quantum mechanics question on probability amplitude

    Homework Statement What physical phenomenon requires us to work with probability amplitudes rather than just with probabilities, as in other fields of endeavour? Homework Equations The Attempt at a Solution That the probability of an outcome is given by the square of the modulus of...
  31. C

    Would a particle at the edge of the universe have an infinite amplitude

    First off let me state that I'm just a mechanical engineering student, so I'm not too savvy when it comes to quantum physics, but my teacher was talking about this equation in class and it reminded me about infinite wavelengths near the egde of the universe and the event horizon on a black hole...
  32. D

    Amplitude Modulation Phenomona

    Hey Everyone, Can someone explain to me the natural of amplitude modulation in regards to sound. As in one modulator frequencies' amplitude modulating the amplitude of a carrier frequency. Because at low frequencies the modulator only affects the carrier in a way that makes its volume go up...
  33. D

    Amplitude Modulation equation help

    Hey everyone, I am trying to understand the phenomena behind the technique of using amplitude modulation in sound synthesis. When you have two frequencies, for example, w1=200hz and w2=300hz, and you use the amplitude of one (w1) to modulate the amplitude of the other (w2), it creates 3...
  34. E

    Amplitude reflection coefficient for high to low refractive index

    For a wave traveling from a medium with refractive index n1 to n2 with n2 > n1, the amplitude reflection coefficient is given by: r = (n2 - n1)/(n2 + n1) Consider a beam of light passing through a single pane of glass. There is a reflection at the front surface of the pane, with the...
  35. L

    What does probability amplitude mean

    I'm not exactly sure what it means when my book says that the wave function ψ(x,t) is a probability amplitude of knowing where the particle is in position x at time t.
  36. J

    What is the amplitude of a sine wave?

    Hi, I want to calculate the amplitude of the following: V(t) = Acos(2wt)+Bcos(3wt)+Ccos(4wt)+Dcos(5wt) Not really sure what approach I can take to do this. I was thinking of using some combination of the double angle formula to simplify each part, but I don't think that will necessarily...
  37. T

    Amplitude of horizontal mass-spring system

    Homework Statement This is a horizontal mass spring system in a simple harmonic motion problem set. Vmax = 20 m/s F = 10 N m = 0.5 kg Find Amplitude (A) and spring constant (k) Homework Equations The Attempt at a Solution I could not figure out a way to solve this problem, and the only...
  38. R

    Maximum possible amplitude of oscillation

    Homework Statement You stick two blocks together with Velcro. The manufacturer rated the Velcro as needing a force of 50N to separate the side you are using when applied to solid surfaces. You set up the connected blocks so that the top one is attached to the end of a vertical spring. The...
  39. E

    FM Amplitude vs. Frequency Spectrum

    I know that an AM Amplitude vs. Frequency Spectrum has a central frequency = carrier frequency and two side bands of carrier frequency ± signal frequency. Now what would a similar spectrum look like for an FM wave ? My textbook just says that '... further side frequencies that are...
  40. H

    Simple Pendulum: Amplitude, velocity, and angular position.

    θθHomework Statement A simple pendulum of mass 20.0 g is suspended by a length of string 1.0 m. It is pulled from equilibrium so that it's raised 10.0 cm and released. Angular position given by θ(t)=θmaxcos(ωt+∅) What is the period? What is the maximum velocity of the pendulum? What is the...
  41. S

    Complex amplitude reflectance of a spherical mirror

    Homework Statement Prove the complex amplitude reflectance of a spherical mirror is given as exp[-jk(x2+y2)/R] Homework Equations Transmittance of a spherical mirror is also exp[jk(x2+y2)/2f] The Attempt at a Solution I have totally no idea how to go about doing this. Can I just...
  42. K

    In circuit A the signal form mic AC (very low amplitude )

    consider two circuits: In circuit A the signal form mic AC (very low amplitude ) is combined with Vbb(to drive the BJT), as the two voltage sources are series they adds up and its amplitude increases and it is passed to bjt and then to loudspeaker. in circuit B the signal form mic AC (very low...
  43. A

    Amplitude and energy relation in optics

    Hi Guys I have a very simple and basic question. Assume interface of two dielectric mediums. If the t is transmition cofficient for electricfield from medium 1 to medium 2 with refractive indexs n1 and n2, what is the transmitivity of power from medium 1 to medium 2? I know it is...
  44. E

    Fourier Series: Small Waves & Equal Amplitude

    In Fourier series we have small waves on the top of big waves (the function seems like that), but the small waves do not have the same amplitude. Does somebody know how to get a function with waves and small waves on the top but with the same amplitude.
  45. J

    Amplitude from a Damped Oscillation

    Homework Statement A damped mass-spring system oscillates at 263 Hz. The time constant of the system is 7.4 s. At t = 0 the amplitude of oscillation is 3.4 cm and the energy of the oscillating system is 11 J. What is the amplitude of oscillation at t = 6.7 s? How much energy is...
  46. N

    Mechanical Waves On a String - Speed, Amplitude, and Power

    Homework Statement A string of mass 38.5g and length 5.60m is secured so that it is under tension of 220N. A wave with frequency 178 Hz travels on the string. Find the speed of the wave and the amplitude of the wave if it transmits power of 140 Watts. The Given answers are: 179 m/s and 1.35 cm...
  47. F

    Superposition of light waves: 90 degrees out of phase, amplitude of resultant?

    Two waves are perfectly superposed (traveling same direction), but are 90 degrees out of phase. Does this result in destructive or constructive interference, as the waves could be seen as either half anti-phase or half in-phase. For example, the first wave has an amplitude of 1. The second wave...
  48. A

    Wave Amplitude from Line Source: Finding Amplitude at Distance '4r

    Homework Statement from a line source, if amplitude of a wave at a distance 'r' is'a'.then the amplitude at a distance '4r' will be what? The Attempt at a Solution i could not understand the pattern of the spreading of the wave from the line source.
  49. S

    Is there a way to know how the amplitude of a wave will evolve?

    It’s very well know that Maxwell equations bring the solution for plane waves but as far as I know I cannot use them to detect how the field would evolve by only looking the E and B fields on the contour of the point under evaluation. Is that possible? My question comes because on a plane wave...
  50. A

    1D oscillator solving for Amplitude

    Homework Statement You are told that, at the known positions x_{1} and x_{2}, an oscillating mass m has speed v_{1} and v_{2}. What are the amplitude and angular frequency of the oscillations? Homework Equations x(t) = Acos(wt - \delta) v(t) = -Awsin(wt -\delta) w =...
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