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. M

    Understanding DTFT Angular Frequency: Mike's Questions

    Hello everyone. Iam trying to understand the discrete time Fourier transform for a signal processing course but Iam quite confused about the angular frequency.If I have a difference equation given, what values should I choose for my angular frequency if I do not know anything about the sample...
  2. N

    I Question about finding resonant box dimensions

    Hello! I hope I'm in the right place for this questions. In short, I'm a musical instrument builder. I'm looking at placing a piece of wood above a closed resonator box. The box (also made out of wood) will have a hole in the top that is centered under the piece of wood. I know the material that...
  3. mishima

    Monitoring a 24 kHz frequency, logging a digital dB reading

    Hi, I had a project in mind but I'm not sure its possible, or what I might need. Current Setup: A small loop antenna monitors a 24kHz (VLF) radio signal, and passes it to an amplifier (schematic can be found here: https://www.physicsforums.com/threads/schematic-symbol-help-supersid.709128/)...
  4. N

    Simple Harmonic Motion: conceptual idea of angular frequency

    One of the conditions to distinguish Simple Harmonic Motion from other harmonic motions is by the relation that a∝x where x is the displacement from the point that acceleration is directed towards But what confuses me is the constant of proportionality introduced to this relation: ω2 ω is...
  5. T

    B Does Zero Rest Mass Mean No Particle Exists?

    If we equate Planck expression ##E = h \nu## with Einstein's ##E = m_o c^2## we get $$m_o c^2 = h \nu$$ what can we conclude from this? Since the frequency ##\nu## above is directly related to the frequency of which a particle will be found at a given point, would the above expr mean that if...
  6. Pushoam

    Angular frequency of a physical pendulum

    Homework Statement For calculating angular frequency of a physical pendulum, I consider its center of mass motion. The COM motion is a simple pendulum motion. Considering a coordinate system whose origin is the pivot point. Then, the COM is the length of the corresponding simple pendulum. Is...
  7. D

    High frequency being transformed to a low frequency

    Hi Physics, I have an idea but before i start. I must know am I right. Is it possible? We have a small room with two objects. The first object is a producer of sound waves out of the human hearing range. This object sends ultra sound waves to the second object. The second object start to...
  8. sophiecentaur

    What actual frequency is my mobile phone service in the UK?

    It's easy to get information about the channels that the various 2G, 3G, 4G services use but I want to find out the actual frequency my service uses in my home. I was hoping to try a 'passive relay' arrangement to bring the (totally rubbish) signal from upstairs to downstairs by my computer. I...
  9. T

    How do i get the frequency of undamped motion?

    Homework Statement The single wheel of an aircraft can undergo a max of 7500N at a vertical velocity of 8 m/s on landing. The vertical spring moves in SHM and has a stiffness of 600N/mm. The systems vertical damper has a damping coefficient of 38 x 10^3 Ns.m-1 Homework Equations F=Kx...
  10. Pushoam

    Frequency of oscillation of a rod with two springs

    Homework Statement Homework EquationsThe Attempt at a Solution Let's take that in equilibrium, both springs S_l and S_r are elongated by ##x_e##. Assuming that the oscillations are so small that the springs could be taken along x- axis approximately. At time t, S_l is elongated by x. The rod...
  11. F

    MHB Calculating Frequency, Midpoint, Relative Frequency and Cumulative Frequency

    Hello, If the lowest class limit is 0-9 then how do I figure out the frequency, Midpoint, Relative frequency, and cumulative frequency?
  12. M

    Real time analysis of mains frequency

    All, I could use some help. I would like to measure mains frequency in real-time and pass the data through a high-level programming language (preference of Python). I am not sure where to start with this project, I assume commercial mains frequency analyzer exist, however, my google searches...
  13. D

    Can sound waves cause a burning effect on some materials?

    Hi, I wonder is it possible sound wave heat material that high that the material goes up in flames? Or what other type of frequency can make some materials burn?
  14. E

    How do you find speed given the beat frequency?

    Homework Statement Using a radar gun, you emit radar waves at a frequency of 2.6 GHz that bounce off of a moving tennis ball and recombine with the original waves. This produces a beat frequency of 730 Hz. How fast was the tennis ball moving? Homework Equations fbeat = fa - fb v=λf f=1/TThe...
  15. H

    Natural Frequency of a rod

    does the natural frequency of a steel rod rigidly fixed will vary when it is assembled with another rod by universal joint?
  16. A

    High K material in High frequency

    Hello all I need a high K material to cancel out E-field in some direction (induced by electromagnetism). This high K material (above 5000) must work in high frequencies above 10MHz. I did use the ceramics but there is no clue that it will work in that range of frequencies or not. I am really...
  17. Cocoleia

    I Rectangular wave, extraction of ions from a stopping cell

    Hello. I'm not sure if this question is to project-specific, but I will try to explain as best that I can. I am working with a system such as this one, with only a few differences: http://www.sciencedirect.com/science/article/pii/S0168583X1400706X it is a cryogenic stopping cell. The part I am...
  18. T

    Why Does a Single Sine Wave Show Multiple Frequencies on a dB Graph?

    So I am just working with a synth and I am having it create a single sine wave. I am then looking at the output on a db vs frequency graph and I would expect the db to only be reading at the frequency of that sine wave, but there are readings from 20 Hz all the way to 2k Hz sometimes(althought...
  19. T

    Dependence of index of refraction on frequency

    ok so recently i was doing dispersion of light and all of sudden something that i always took for granted came across the fact that blue light refracts more than red light then i recalled snells law and realized that it had no terms with the quantity of frequency in it (n sin θ = c) then i...
  20. Const@ntine

    Δt between consecutive frequency configurations

    Homework Statement At a long, vertical tube, water is poured in, with an inflow R = 1.00 L/min = 1.67 * 10-5 m3/s. The radius, r = 5.00 cm. At the open end, a tuning fork is oscillating with a frequency of f = 512 Hz. What's the time difference between two consecutive configurations, while...
  21. Const@ntine

    Frequency of Trucks Overtaking a Cyclist

    Homework Statement Garbage Trucks, one after the other, are heading for the dump. They move at 19.7 m/s, and every 3 min, 2 of them arrive at the dump. A cyclist, moves at 4.47 m/s, heading for the dump as well. a) With what frequency do the trucks overtake the cyclist? b) What if there was...
  22. Passionate Eng

    Resonant frequency of small particles

    Hi How can find the resonant frequency of small objects like dust particles? What factors affect the resonant frequency? And is resonant frequency dependent on size? i.e. if the resonant frequency of 1 cm3 of glass is some certain value, would it be the same for a larger size?
  23. lawlieto

    I Are any electrons ejected below the threshold frequency?

    I've been reading about the photoelectric effect, and something got me thinking. If the frequency of light shone onto the metal is below the threshold frequency, no electrons are liberated from the surface of the metal, since electrons absorb quanta of energy, so if that light is shone for a...
  24. shihab-kol

    What Is the Nature of Black in the Visible Spectrum VIBGYOR?

    In the visible spectrum VIBGYOR, there is no black colour.So, what do we percieve as 'black' ? Another of my queries is that when dispersion takes place there is a change in wavelength but not so in case of frequency. But they are related inversely. So, why does this happen?
  25. M

    Faraday Cage Effectiveness versus Frequency

    If inside of a metal (for ex. Aluminum) enclosure, could it potentially create more harm than good if frequencies were able to penetrate due to an imperfectly sealed cage or due to a relatively high power level of frequencies that allowed them to penetrate the metal? If the power level was high...
  26. c704710

    B Light Beams Attraction: e=mc^2 & Asymmetry

    Appearently, two beams of light in a vacuum are attracted to each other. Photons have no Newtonian mass, but their relativistic mass (e=mc^2 or mass-energy equivalence) causes this (as is my understanding). So will a 10^4 Hz beam bend more towards a 10^20 Hz beam than the 10^20 Hz bends towards...
  27. fisher garry

    Deriving Larmor frequency problem

    I don't get how they get Eq. 5. Why is the direction of ##\mu## going outwards from the direction of B? And why does the fact that ##\frac{d\mu}{dt}## is perpendicular to both ##\mu## and ##B## mean that ##\mu## goes in circle?
  28. F

    Calculating angular frequency and velocity after a collision

    Homework Statement The Problem is the following: We have a uniform disk of radius r laying still with its center at the origin. Two bullets, with equal mass m and negligible size are approaching the disk, both with trajectories parallel to the x-axis and at distance h, -h from the y-axis...
  29. C

    Relating resonant frequency to electrical impedance

    If a self oscillating electrical (passive) system is excited at two nodes A and B by a sinusoidal current, and if this system has one degree of freedom, then the response of the system is maximal at the resonance frequency. Quantitatively, this means that the ratio of the exciting complex...
  30. M

    Understanding Frequency and Waves in Physics and Engineering

    Let ##f## denote frequency and ##p## denote period. Then ##f=1/p##. Given some wave, say ##\sin( \beta t)##, most publications refer to ##\beta## as the frequency. But we know ##p=2\pi/\beta\implies f=\beta/2\pi##. Do most physicists and engineers omit the ##2\pi## part? Thanks!
  31. DaTario

    Why there is no frequency for the color brown?

    Hi All, Is it true that the brown color has not a single frequency attached to it?DaTario
  32. Sveral

    Resonant frequency of Volatile organic compounds

    Hello , could someone tell me ,where to find Resonant frequency of the chemical bond of the following Volatile organic compounds: Propene,Toluene,Benzene,Ethylbenzene. Thanks in advance .
  33. A

    Resonant Frequency and Transfer Functions

    Suppose I have some sort of a filter, whose transfer function is given by H(w), where w is the angular frequency of the input signal in radians per second. I want to know the maximum value of the transfer function. If I solve for the resonant frequency w0, which from my understanding is the...
  34. mpolo

    How to calculate the Doppler Shift Frequency

    I would like to know the formula for calculating the Doppler shifted frequency received by someone on Earth that is received from a spaceship traveling at 85 percent the speed of light away from Earth. Please show example of the formula being used. Let's say the spacecraft sent a radio signal...
  35. T

    MOSFETs pulsing at a frequency out-of-phase

    <Moderator's note: Spin-off from a related thread: https://www.physicsforums.com/threads/h-bridge-diodes-or-rather-the-lack-of.915992/> I've always wondered: What do people usually use for gate drivers for mosfets and H-Bridges? For example; say I wanted to have a couple MOSFETs pulsing at a...
  36. Tulio Cesar

    Relation between sound intensity and frequency

    The sound intensity formula is given by: dE/dT*dS. So the variables are energy, related to the amplitude of the wave, area, related to wavefronts distribution on space, and time. So many times I don't see any reference about the relation between frequency and sound intensity, but if time is a...
  37. Adam Rabe

    Tone hearing frequency concept question

    Homework Statement Homework Equations Dont know any sorry The Attempt at a Solution I tried imagining the ear as some sort of harmonic pipe with the sound coming inside as a sine wave. The question says the sine wave is not fully sinosoidal and is flattened at the top and bottom. I don't...
  38. G

    B Add two functions, same frequency to produce one greater?

    Is their any way to add two wave functions like sin or cos in such a way that you could double the frequency or at least increase it?
  39. Manolis

    Driving a neon bulb with high frequency

    I want to produce a 100 volt peak to peak symmetrical AC waveform to light a miniature neon bulb. It strikes at about 90 volts then settles ("clamps") at about 50 volts, according to the spec. I want the frequency to be at least 10 kHz for easy filtering because the circuit will also be passing...
  40. chem31sa6

    Hearing the Train Whistle Frequency: Calculating fs

    Homework Statement You are standing on a train station platform as a train goes by close to you. As the train approaches, you hear the whistle sound at a frequency of f1 = 92 Hz. As the train recedes, you hear the whistle sound at a frequency of f2 = 79 Hz. Take the speed of sound in air to be...
  41. Pushoam

    Variation of EM radiation with frequency

    Homework Statement X-ray pulses, visible-light pulses, and radio pulses (the latter corrected for dispersion in the interstellar plasma) emitted by an astronomical object called a “pulsar” are all observed to arrive simultaneously at the Earth — with an uncertainty of only 200 microseconds. The...
  42. Pushoam

    Range of frequency of electromagnetic waves

    Theoretically speaking, does the frequency of em wave range from 0 to infinity?
  43. W

    Flute player initial frequency?

    Homework Statement A flute player hears four beats per second when she compares her note to a 587 Hz tuning fork (the note D). She can match the frequency of the tuning fork by pulling out the "tuning joint" to lengthen her flute slightly. What was her initial frequency? Homework Equations Not...
  44. O

    What is the relationship between frequency range and GBW in amplifiers?

    I have an op-amp with frequency range 20Hz - 20kHz. Is frequency range the same as bandwidth?
  45. ltnghia1304

    The frequency of two parallel springs and one weight system

    Homework Statement I want to find the angular frequency of the system below Homework Equations F = -kx U = 1/2*k*x^2 The Attempt at a Solution But here's the answer: I don't know how come this solution. Any one help me? Thank you so much.
  46. D

    What Is the frequency of red light?

    Homework Statement The speed of light in a vacuum is 3.00x(10*8)m/s. Using the equation v=fxλ, calculate the frequency of red-light. (I was told to use the wavelengths given from textbook) Wavelength/λ =700nm v=300,000,000 <-- ( I need help understanding this. Is this a rate? Or?) Homework...
  47. Mzzed

    Superposition's effect on frequency?

    Imagine two electromagnetic waves are traveling in opposing directions such that they eventually meet, overlap, and continue traveling as usual after the superposition/overlapping event. Just before they overlap there is some superposition effect taking place but not enough to fully merge the...
  48. RyuuJin

    A Gravitational waves: effect of frequency on strain

    Hi guys. I am having a little trouble understanding a few relations professor mentioned at lectures, regarding gravitational waves - flux of energy and strain. First one expresses how is the flux of energy F related to frequency of radiation f and inflicted strain h. And the second one is for...
  49. G

    Sound absorption coefficients differing with frequency

    Hi there, my understanding of absorption coefficients is that harder materials generally reflect more sound similarly to how a harder material will result a ball to bounce higher than a softer material. What I am having trouble finding research on and understanding is the reasoning behind the...
  50. Isaac0427

    Why don't I hear beats when singers or instruments play the same note?

    Consider this: two singers are both singing an A4. These singers, like any human, are not perfect. One sings 440 Hz and one sings 441 Hz. So, theoretically, I should hear an amplitude oscillation with a frequency of one second, right? I never seem to hear this kind of effect, though it should...
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