What is Frequency: Definition and 1000 Discussions

Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as temporal frequency to emphasize the contrast to spatial frequency, and ordinary frequency to emphasize the contrast to angular frequency. Frequency is measured in hertz (Hz) which is equal to one event per second. The period is the duration of time of one cycle in a repeating event, so the period is the reciprocal of the frequency. For example: if a newborn baby's heart beats at a frequency of 120 times a minute (2 hertz), its period, T—the time interval between beats—is half a second (60 seconds divided by 120 beats). Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio signals (sound), radio waves, and light.

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  1. Elvis 123456789

    Determining angular frequency and amplitude for SHM

    Homework Statement A mass "m" is attached to a spring of constant "k" and is observed to have an amplitude "A" speed of "v0" as it passes through the origin. a) What is the angular frequency of the motion in terms of "A" and "v0"? b) Suppose the system is adjusted so that the mass has speed...
  2. Biker

    Why doesn't the frequency change after refraction?

    I would like to know why the frequency of a wave doesn't change after a refraction. I have seen some arguments about Energy conservation that in order to conserve energy "Assuming no reflection" the same amount of waves must be coming out in the same time. But That raises a question, Why can't...
  3. Destroxia

    Planck's Law: Low, and High Frequency Limit

    Homework Statement a) Derive the Rayleigh-Jeans distribution by taking the low-frequency limit of Planck's distribution. b) Derive the Wien distribution by taking the high-frequency limit of Planck's Distribution. Homework Equations ## u(f) = \frac {8 \pi f^2} {c^3} \frac {hf} {e^{\frac...
  4. Clara Chung

    Why wave with lower frequency produce heat?

    why wave with lower frequency produce heat? please explain to me
  5. H

    Calculating Pulse Transformer Frequency at Voltage

    Hi. I need some help in explaining in a simple way how to calculate the minimum allowable frequency at a certain voltage when selecting a pulse transformer. The one I'm looking at has an ET value of 45Vusec. I'm feeding it 22.5KHz at +/-6VAC square wave. It seems to work fine but I fear it is...
  6. E

    How to graph amplitude vs. frequency for a Low-Pass Filter?

    Homework Statement For my lab class my professor wants us to graph the theoretical amplitude of the output from a low-pass filter vs. frequency. I have the resistance and capacitance that I chose for the RC circuit and a V(in). Is there an equation that I should be able to use to relate these...
  7. F

    Mechanical waves-relation between frequency and power

    so i do understand clearly that the higher the energy of a wave , the higher the amplitude ... but what i was not understanding is how we can create a wave that performs 50 oscillations per second with the same amount of energy that we use to form 1 oscillations per second , with both waves of...
  8. Mohamed_Wael

    Air Resonance Frequency: Effects of Excitation

    I wonder of the air has resonance frequency or not, if yes what would happen if we excite it at this frequency
  9. khurram usman

    A Finding the frequency of sinuosid in a constant + sinusoid?

    Hi everyone, I am working on some problem relating to radars. The problem boils down to finding the frequency of the complex exponential in a constant + complex exponential + noise model. I found some papers on sinusoid recognition but they use the sinusoid + noise model only. I tried to come...
  10. W

    Natural frequency of a mass spring system

    Homework Statement Homework Equations T = 2π√(m/k) mx'' + kx = 0 F = ma The Attempt at a Solution I don't honestly know where to start with this. I'm really out of my league in this class, and I'm trying my best to catch up with the things I didn't quite master in Dynamics and Physics... As...
  11. Metals

    I Blue lights (LEDs) consume more power than red (and green)?

    Referring to LEDs as I'm not aware of any other "colour-producing" light, does blue light use more energy than red light? Planck's formula (E=hf) leads me to believe that blue light would drain a battery quicker than red, due to its higher frequency. Surely a device emitting blue light would...
  12. Planobilly

    How to select a ferrite bead to suppress high frequency

    Hi guys, I see ferrite beads used on the input of V1 on some high end tube guitar amp designs without any indication of type and value. Can you give me some idea how to select this component and at what other places in a tube amp it could prove useful? Thanks, Billy
  13. H

    Inertial frame where plane waves have the same frequency

    Homework Statement Plane harmonic waves of 1/p, 1/q, 1/r and 1/s are travelling, respectively, in the directions of the (non-unit) vectors (1,1,1), (1,-1,-1), (-1,1,-1) and (-1,-1,1). Show that there exists an inertial coordinate system in which they have the same frequency if and only if...
  14. K

    AC Output Voltage as function of frequency

    Homework Statement Given a sine-wave generator of frequency f having internal resistance R1 connected to a high-pass filter. If the generator shown in the dotted outlined box produces a voltage V0(t) = V0 cos(2π ft) with no load, derive an expression for the output voltage V1(t) = V1 cos(2π ft...
  15. R

    Understanding Electromagnetic/X-Ray Pulse in Time and Frequency Domain

    Dear All, Suppose we have a electromagnetic/x-ray pulse with fixed energy with finite line width. I want to know the schematic of a plot how it looks in time- and frequency-domain? I think I understand in time domain: there will a straight vertical line on plotting intensity vs time in x-axis...
  16. R

    MHB Construct a frequency distribution using 5 classes

    41 35 29 43 16 49 32 6 20 10 26 28 47 43 7 36 13 10 0 2 The data represent the time, in minutes, spent reading a political blog in a day. Construct a frequency distribution using 5 classes. In the table, include the midpoints, relative frequencies, and cumulative frequencies. Which class has the...
  17. R

    Resonant frequency of Piezoelectric material

    So i have a piezoelectric film deposited in the metal substrate and i want to determine the resonant frequency. Basically i can determine the resonant frequency base on the dimensions. But i need to proved it using experimental set-up. So i applied AC Voltage to the material then the material...
  18. F

    Intuitive reasoning for frequency remaining constant during refraction

    What is the intuition for why the frequency of light does not change as it passes from a less dense medium to a denser one (or vice versa)? Classically, if we treat light in terms of waves, then intuitively, is the reason why the frequency does not change because it is determined by the...
  19. F

    Half power frequency divides by sqrt(2) instead of 2 why?

    Homework Statement Problem is to find the half power frequencies of a RLC circuit. Z = √(R2 + (WL-1/WC)2) 2. Homework Equations Power(P) = V2/Z Pmax = V2/R <---because Z min = R The Attempt at a Solution P/2 = V2/2R = V2/Z Z=2R (R2 + (WL-1/WC)2) = 4R2 (WL-1/WC)2 - 3R2 = 0 W2-3WR/L-1/LC = 0...
  20. Ecthe

    Atomic units of frequency and angular frequency

    To calculate the Keldysh parameter, I need to use the optical frequency of a laser in atomic unit. Since for the time: 1 a.u. = 2.42×10-17 s, I would assume that for the frequency: 1 a.u. = 4.13×1016 s-1 which is juste the inverse of the time one. However, I found several sources such as...
  21. Kfir Dolev

    Combine capacitors and inductors to be frequency independent

    Is it possible to combine (possibly infinite) capacitors and inductors to get a total impedance which is independent of frequency. If so, how?
  22. N

    I Eigenvalue as a generalization of frequency

    Hello everyone. I understand the concept of eigenvalues and eigenvectors, using usually a geometric intuition, that a eigenvectors of a matrix M are stretched by the corresponding eigenvalue, when transformed through M. My professor said that eigenvalues represent a generalization of the...
  23. T

    Common source amplifier low frequency resonse

    Here's the amplifier in question: I'm not understanding this part: Why is Cs not included in the current divider ? To my understanding of current divider, It = Id+Io, where It is the current flowing through Rd So, Io = It*(1/Cs)/(1/Cc2)+RL
  24. N

    Troubleshooting a High Frequency Mixer: Oscilloscope Output Analysis

    Hi all, I am making a frequency mixer to add together channels of an amplifier I have at 52.892kHz. I am attaching a picture of the schematic and the physical circuit I made along with the output on the oscilloscope I am measuring. Instead of the three outputs shown in the schematic, I am just...
  25. B

    MHB Probability Activity Word problem for relative frequency

    I am drowning in math right now and would love some help bc I am horrible at math. Here is what I have got. Question: 1. The four major blood groups are designated A, B, AB and O. Within each group there are two types; positive and negative. Find data on the relative frequency of these eight...
  26. K

    Sound frequency from distance b/w first minimum and maximum

    Homework Statement Two speakers are arranged as shown. For this problem, assume that point O is 12 m along the center line and the speakers are separated by a distance of 1.5 m. As the listener moves toward point P from point O, a series of alternating minima and maxima is encountered. The...
  27. L

    Frequency Control in Power Plants -- Droop

    Hi, how do power operators change the droop setting in modern power plants? Back in the days it was with help of a flyball governor(?). In todays power plants do operators adjust some sort of gain electronically via a scada system or something?
  28. R

    Vibrational frequency of Piezoelectric effect

    when a piezoelectric material experience a stress it generates voltage, and also when you applied voltage the piezo-material experience a vibrational frequency. Using oscilloscope we can determine the induced frequency of the piezo-material with respect to the applied voltage. Now given the...
  29. S

    Fundamental frequency change because of bouyant force

    Homework Statement A rope has an end fixed and the other is passing through a pulley and has a body attached to it. The fondamental frequency of the rope is initially ##f_1=400 Hz##. If the body is then put in water the fondamental frequency of the rope becomes ##f_2=345 Hz##. If the linear...
  30. D

    Factors affecting the resonating frequency of wire?

    Homework Statement We have done the experiment about this but now we have to do a report on it. Not a basic or simple but a report with a professional standard. I did mine but its to simple. I started it again but its too short so i was wondering if someone can give me a start on the physics...
  31. T

    Linearising Graph of Mass and Frequency

    Homework Statement I did an experiment about the loading of tuning forks. I added blue tac to one of the prongs on a tuning fork and then weighed it. I then measured the different frequencies for each mass and plotted a graph which ended up looking like a exponential decay graph. The results...
  32. Y

    How to understand negative frequency?

    Recently I learned some communication theory, which uses negative frequency, what does negative frequency means? So I checked textbook, found the negative frequency comes from the Fourier transform, which comes from the euler formula, e-jx=cosx+isinx, or another form cosx=(ejx+e-jx)/2, then any...
  33. entity314

    Frequency appears to have to effect on hysteresis

    This question is primarily regarding transformers, particularly the impact frequency has on hysteresis loss. Given hysteresis loss = η×Bmax×f×V and Bmax = (V ×〖10〗^ 8)/(√2 π×f×N×A) This means that hysteresis loss = η (V ×〖10〗^8)/(√2 π×f×N×A) fV = (η ×〖10〗^8)/(√2 π×N×A) V^2 And as such...
  34. P

    A Frequency analysis of signal with unknown period

    I was reading up on (discrete) Fourier transform when my mind started to think of an what-if scenario: Assumed I'm sampling a signal of the form a1*sin(b1+c1) + a2*sin(b2+c2) + a3*sin(b3+c3) + ... + aN*sin(bN+cN) + some noise where the a's represents magnitudes, b's represents frequencies and...
  35. petrushkagoogol

    A Nature of radiation emanating from a body v/s frequency

    Does the nature of radiation emitted by dense bodies like black holes differ in frequency from radiation emitted by regular stars like our Sun ? I believe that the former radiates more x-rays and high frequencies rather than the latter which radiates mainly uv, visible and infrared ranges. Is...
  36. Hongo

    I Radio Comm Between 2 Points Diff Gravity: True?

    A source that is orbiting close to a singularity of a black hole is transmitting a radio frequency signal that lasts 60 seconds and is repeated infinitely. The signal is being transmitted using the amplitude modulation method (AM Radio). Let suppose that each minute passing in the transmitting...
  37. S

    Doppler shift and change in intensity of a sound wave

    How are the intensity of a sound wave and the Doppler shift of frequency related togheter? That is, if the source or the observer are in relative motion, how does the intensity change? For a sound wave $$I=\frac{1}{2} \rho \omega^2 A^2 c=2 \pi^2 \rho f^2 A^2c$$ (##c## is sound speed, ##\rho##...
  38. S

    I Doubts on wavefunction conditions

    I'm facing some difficulties in using "boundary conditions" in a simple wavefunction. The wavefunction I'm considering is $$\xi(x,t)=A sin (k x \pm \omega t +\psi)$$ The minus or plus are for progressive or regressive waves. The indipendent parameters are 4: ##A##, ##k##, ##\omega##, ##\psi##...
  39. S

    Device that detect waves in a frequency range and beats

    Homework Statement You have a device that can measure sound waves only if the frequency of the wave is in the range ##0.8 kHz- 20 kHz##. You have a whistle that produces sound waves at ##21.5kHz##. You ride a bike moving away from a wall, at the same time you blow the whistle and hold the...
  40. S

    Beats: frequency of resulting wave vs. beats frequency

    The beats frequency heard from the interference of two sound waves with frequencies ##f_1## and ##f_2## is $$\nu=|f_1-f_2|$$ Nevertheless the frequency of the resulting wave is not ##\nu## but the mean value of the two frequencies $$f_{resulting}=\frac{f_1+f_2}{2}$$ As far as I understood...
  41. ahmed tb

    Determination of the natural frequency of a Hartnell governor

    Homework Statement Homework EquationsThe Attempt at a Solution I found this solution for the nature frequency but here it does not include the Ball weight and centrifugal force in the moment balance equation about the pivot (O), it is wrong answer...is not it? I tried to solve the problem...
  42. V

    Bohr frequency of an expectation value?

    Homework Statement Consider a two-state system with a Hamiltonian defined as \begin{bmatrix} E_1 &0 \\ 0 & E_2 \end{bmatrix} Another observable, ##A##, is given (in the same basis) by \begin{bmatrix} 0 &a \\ a & 0 \end{bmatrix} where ##a\in\mathbb{R}^+##. The initial state of the system...
  43. D

    Getting frequency from angular momentum?

    Homework Statement [/B] I messed up the original thread in terms of information, so I made a new better one. Ok here goes: I have a problem where a right circular cylinder with diameter .115meter and a mass of .03kg is rotating at 300 rev per min. Now an Ant which weighs .01kg collides with...
  44. D

    Final Frequency and Kinetic energy change?

    Homework Statement Hi I know my picture has 2 problems, but let's just focus on the first problem parts a and b. So for part a it ask for the final frequency after the ant landed, and part b is the kinetic energy difference. Basically the ant=.01kg, diameter of cylinder is .115m, the weight of...
  45. Roy Fokker

    How can I adjust the roll off of my preamp design for better frequency response?

    Hello I am developing a low noise preamp and would like to change the roll off of my design to sharply decrease the gain for very low frequencies "1-5Hz". The results of my current design are as follows. I would need something that looked more like this.. I understand the simple equations...
  46. E

    I Pound-Drever-Hall frequency stabilisation technique

    I am having some difficulty understanding the Pound-Drever-Hall frequency stabilisation technique, when locking a laser to a stable cavity. As far as I understand: We emit the laser frequency, f0. This signal is modulated with sideband frequencies, ± fm. This is fired towards the Fabry-Perot...
  47. E

    I LIGO light changes frequency not wavelength

    Gravitational wave stretches and shrinks space. Why Laser light in Ligo arms changes frequency, and not wavelength.Is it some clear explanation? If even frequency would not be changed than spacetime is not changed, I suppose. What cannot be measured, cannot exist.
  48. P

    What is the equation for electromagnetic wave frequency?

    Hi there When a charge is accelerated it produces electromagnetic radiation. I was wondering if anyone knew the equation relating the frequency of emitted radiation to the size of the charge and the value of the acceleration. My understanding is that it relates to Maxwell's equations, but I was...
  49. C

    Frequency of wire oscillations

    Homework Statement There's a horizontal thin wire whose mass is negligible and whose length is l=1m. It is strained with constant force F=10N. If we place a tiny pellet in the middle of wire (mass of pellet is m=1g) and then we bring wire out of equilibrium position (moving out of it's original...
  50. P

    What is the equation for working out emf frequency

    Hi there My understanding is that any charge will produce some emf when it is accelerated..is this always true? What is this law called? Is there a simple equation to relate charge size, acceleration rate and resulting emf frequency? Many thanks
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