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. I

    Angular frequency of a non-sinusoidal pulse

    Hey all, so I’ve been learning nonlinear acoustics and have encountered a conceptual hurdle in my studies. When using a model, such as a form of the classical Burgers equation, to propagate sound waves, you generally have a “characteristic angular frequency” in the equation (often represented by...
  2. S

    Difference between angular velocity and angular frequency

    I have seen so many questions and confusion about the difference between angular velocity/speed and angular frequency. Usually, answers were always given in the context of uniform circular motion (angular speed) and simple harmonic oscillation (angular frequency), but this is what causes the...
  3. entropy1

    I Frequency spectrum of phase shift

    What does a 180 degree phase shift of a sinusoidal in a signal do to the frequency spectrum of the signal?
  4. S

    How Do You Calculate Oscillation Frequency for a Quadratic-Cubic Potential?

    Homework Statement A particle moves in 1D in a potential of the form $$U=Ax^2+Bx^4$$ where A can be either positive or negative. Find the equilibrium points and the frequency of small oscillations. Homework EquationsThe Attempt at a Solution So the equilibrium points are obtained by setting...
  5. S

    Explaining Temperature Increase with Antenna and Tissue

    Hi; Let's imagine that I have an antenna and a biological tissue. The antenna emits the frequency of 1e7 Hz and I have a temperature increase x. When the antenna emits the frequency of 3e7 and 6e7 Hz the temperature increase is the same. How can I explain?
  6. A

    AC circuit, voltage and frequency problem

    Homework Statement According to Equation 20.7, an ac voltage V is given as a function of time t by V = Vo sin 2ft, where Vo is the peak voltage and f is the frequency (in hertz). For a frequency of 64.7 Hz, what is the smallest value of the time at which the voltage equals one-half of the...
  7. V

    Does the sound or the frequency to repel mosquitoes exist?

    Hi, I have heard much about this, but I'm not an expert. Now I know that mosquito hears by Johnston's organ at antennas. Also that mosquitoes have something like "sound/frequency filter", it means they listen to only some sound/frequency, especially other mosquitoes or other animals. Is it...
  8. Adoniram

    Determination of the frequency of a sampled signal

    Hello everyone, I have a question regarding data reconstruction over RF, especially in the case of FM. Let us say I have a trivial case where I have a carrier frequency of fo and a bandwidth of fbw. I want to setup a scheme such that fo + fbw is a 1 and fo - fbw is a 0. (I'm naively under...
  9. S

    Frequency and energy of EM radiation

    Am I correct that the direct proportionality between the energy and frequency of an EM wave can be obtained from classical electromagnetism? Of course there's the Planck–Einstein relation ##E = h \nu## for a photon, but that entails QM. I'm wondering about the relation ##E \propto \nu## for an...
  10. A

    Harmonic Frequency of a String

    Homework Statement A string (m = 1 kg) fixed at both ends is vibrating in its second harmonic mode. If the length of the string is 2 m and it feels 50 N of tension, which of the following is NOT a possible harmonic frequency for this string? a) 1.25 Hz b) 2.5 Hz c) 5 Hz d) 10 Hz e) 20 Hz...
  11. R

    Electrical How to build your own high frequency oscilloscope

    Does anyone know if there is a textbook on the design and construction of high frequency oscilloscopes (up to 10 GHz)? I am guessing they would be some form of ADC circuit with perhaps a mixer and could use a lap top as the "DSP" and display. How would such an O-scope be calibrated/tuned...
  12. G

    Frequency spectrum of a clarinet

    Hi. Usually, the clarinet is presented as acting like a pipe system closed at one end, which only allows for harmonics that are odd multiples of the fundamental frequency. I used the app "SpectrumView" by OxfordWaveResearch to measure the following spectrum: Fair enough, the amplitudes of the...
  13. Turukano26

    Calculating the frequency of a free electron

    I feel like I must be missing something obvious, but I can't figure it out. I have the speed of an electron, and to calculate its frequency i used p = h/λ, then subbed in p =mv and λ= v/f. Giving me the equation f = mv2/h. However, I also could use E = 1/2 mv2 and E = hf to give me the equation...
  14. T

    Natural frequency in stationary and rotating frames....

    Hi, I am trying to gain insight into using stationary vs. rotating coordinate frames for natural frequency calculations. I have seen many FE codes suggest that critical frequencies can be calculated differently in rotating and inertial frames, so i wanted to do a 1D calc to see for myself how...
  15. E

    Why the Frequency of Light Does Not Change Through a Medium

    My question is about why the frequency of light or another EM wave does not change while passing through a medium. We know their Speed decrease and wavelenght change but think about this analogy for ex i am 4 meters high and drop 5 balls in 5 seconds and my friend waits at ground he will receive...
  16. T

    Xc and XL relation after a change of frequency

    I am getting ready for exams and I have encountered this problem on the exam paper: In AC circuit there is a condensator and a inductive coil, At first XL=XC, how does the relation change when the frequency doubles? The answer says XL=4XC Can someone explain me how they come to this conclusion...
  17. W

    I Frequency of nearby Supernova Explosions

    I have heard an interesting claim that looks fishy to me. The claim is that during the last 10,000 years there hasn't been a single Supernova eruption closer than about 5,000 light years. And that somehow this is an anomaly. That the background rate of nearby supernovas is much higher. And so...
  18. blainiac

    High Frequency Electromagnet Possible?

    I was wanting to build a very high frequency electromagnet to test an idea and it requires something in the range of about 1-10 GHz, and I'm unable to find much information on what I'm attempting to do. I understand the impedance will be incredible, along with some other technical issues. Most...
  19. K

    Unfingered Guitar String Vibration Frequency: 627 Hz

    Homework Statement When unfingered, a string on a guitar vibrates at 627 Hz. What frequency will the string produce when fingered one third of the way from the end, that is only two thirds of the string can vibrate? Homework EquationsThe Attempt at a Solution I am not too sure what equations...
  20. S

    Calculating frequency of the second harmonic

    Homework Statement The fundamental frequency of a violin string is 283 Hz. Calculate the frequency of the 2nd harmonic. Known: f = 283 Hz Homework Equations v = fλ f(n) = n*v/2L λ= L v(sound) = 343 m/s The Attempt at a Solution λ = 343/283 = 1.21 m f(2) = 2*343/2*1.21 = 283 Hz. I'm getting...
  21. T

    I What would be a useful application for 10 Thz nano-antennas?

    Reading: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3597338/ However I don't understand what a useful application for this is? can someone explain?
  22. H

    Frequency for resonance to occur

    Homework Statement That is a speaker. Sound wave is sent out from spesker S into pipe of uniform thickness. Piston P move to left 1st resonance at 0.045 m 2nd resonance at 0.151 m Frequency of the sounx 1620 Hz Piston is stopped at the position that 2nd resonance occur Then, frequency...
  23. A

    A Why is ##\omega_c \tau >>1## for several revolutions?

    Hey, I read about charge carriers in semiconductors in a magnetic field. They write that for several revolutions ##\omega_c \tau >>1## holds. But I think for one revolution it is ##\omega_c \tau = 2 \pi##. (##\tau## is the scattering time) Why they do not write ##\omega_c \tau >> 2 \pi##...
  24. B

    Derivation of resonant frequency for SHM systems

    Homework Statement My question here isn't a specific question that has been given for homework, but a more general one. For an assignment I have to 'derive an expression for the resonant frequency, ω0' for two different systems, the first for 'a mass M connected to rigid walls via two springs'...
  25. Ari

    Frequency of a standing wave based on slope?

    <Moderator's note: Moved from a technical forum and thus no template.> I've done an experiment on standing waves on a string. By graphing √T vs λ (where T is tension and λ is wavelength) using the linearized equation √T = (1/√μ) f ⋅ λ, I was able to get this data: μ = .000256 kg/m slope = 1.78...
  26. MattIverson

    Electromagnetic Radiation of Single frequency Incident on a Slab

    Homework Statement The problem is state in the attachment. Homework Equations None to add. 3. The Attempt at a Solution Struggling with this problem because of the phasor part of it. Perhaps this is justified because the angle is very small and so that relates to a low frequency? Is it...
  27. prodo123

    Frequency at which no destructive interference occurs

    Homework Statement Two speakers A and B, 2.00 m apart, produce a sine wave at the same frequency and phase. A microphone is placed on the line BC perpendicular to AB, at a distance x from B. The speed of sound is v=344 m/s. For a frequency ƒ low enough, there will be no destructive...
  28. S

    Frequency of a wave at resonance

    Homework Statement A 1.2 m tube is closed at one end. A stretched wire is placed near the open end. The wire is 0.330 m long and has a mass of 9.6 g. It is fixed at both ends and oscillates in its fundamental mode. By resonance, it sets the air column in the tube into oscillation at that...
  29. sweet springs

    Electromagnetic field and frequency

    Electromagnetism gives the energy density ##\frac{\epsilon_0}{2}E^2+\frac{1}{2\mu_0}B^2##. It does not include frequency ##\nu## or ##\omega## at least explicitly that QM or photon needs. For an example static electric field has nothing to do with frequency but has energy. How should I...
  30. D

    B Showing/proving a physical relationship

    I derived a relationship between frequency and tension of a string, accounting for tension's effect in the linear density of the string. So in a nutshell, the equation is more complicated and is in the form of f^2=aT^2+bT (f is frequency, T is tension, ab are constants involving the control...
  31. Tannerbobanner

    How does radius affect frequency in uniform circular motion?

    I am writing a lab report on the effect of the radius of a string on the frequency of rotation on an object in horizontal uniform circular motion. My hypothesis is: If the radius of the string from the origin of rotation increases, then the frequency will decrease because frequency has an...
  32. D

    Instrument to measure the frequency of sound

    I need an instrument to measure the frequency of the sound of a vibrating violin string for a high school research essay. I tried using a Labquest and a vernier microphone to measure but it was way too imprecise. I need the instrument to very accurate in measuring Hz as the nature of my essay...
  33. Vital

    I Reading the vertical data in a frequency histogram polygon

    Hello. Please, take a look at the screenshot from the textbook. They say in the textbook that there are in total 48 data observations, 20 of which lie in the interval 0 - 2, and 6 lie in the interval 2 - 4. Yes, both 20 and 6 are more or less clear on the graph, but how did they come up with 48...
  34. D

    Tension and frequency of a vibrating violin string

    1. The problem statement, all variables, and given/known data So I'm doing an IB extended essay on the relationship between frequency and tension of a violin string. As you apply more tension to the string (using weights and pulley), the frequency will be higher, as shown below. There's not too...
  35. I

    Simple Harmonic Motion/Fundamental Frequency

    Homework Statement A tuba is a instrument that can be modeled after a closed tube and has a length of 4.9m. A frequency of 122.5hz produces resonance in the Tuba. Is this the fundamental frequency of the instrument? If not, what harmonic is it? Homework Equations f=λv 4l=λ(open closed tube) v=...
  36. S

    Y-intercept of a lambda square VS tension of standing wave

    Hi all! I am doing an experiment where we create a standing wave by attaching a string to a hanging mass at one end and to a string vibrator at the other (the string passes through a pulley). When plotting the graph, the slope is inevitably 1/(u*f^2) where u is the linear density and f the...
  37. Shadow89

    Optimal values for power in an induction heater?

    I really want to build a simple but powerful induction heater for hobby blacksmithing. Metal shaping and the design of the cooling system within the coils are not a problem. I need help understanding the electronics Obviously I must first use a transformer as a safety against "backlash" to the...
  38. Fernando Calvario

    How to find Angular Speed when given frequency?

    Homework Statement A floral clock in Japan has a radius of 15.5 m. If you ride a bike around the clock, making 16.0 revolutions in 4.50 min, what is your average angular speed? Homework Equations ω = velocity/radius ; 1 rev=2*pi rad The Attempt at a Solution (16 rev*2*pi rad)/270 secs = 0.372...
  39. D

    SHM and why does the frequency not decrease?

    Hello, I don't get it why does the frequency not decrease? As this i assume is damping and frequency must change. And why do only positive peaks decrease?2 Not sure about equations needed. 3.I thought that as it is damped, Energy is lost as heat. Thus speed decreases, therefore, it takes a...
  40. PrathameshR

    Confusion about two modes of coupled oscillators having same frequency

    I am studying coupled oscillations and one of the refrance I'm using says that two modes can have same frequency whereas the other one says it's impossible to have same frequency for two modes. Please help.
  41. John mcgarvie

    Is it possible to transmit frequency of a solid object?

    Hello I'm asking if the resonate frequency of a solid object say a rock. Can be transmitted/guided to change the natural frequency of an object say a rock with a different frequency. And I hope this is a proper question.
  42. gmalcolm77

    I Photon Frequency: Can a Photon Change Color?

    Can a photon ever change frequency? What I mean is, can say a photon of red light ever become a photon of green or yellow light?
  43. entropy1

    B Oscillations in a driven spring

    If I have a spring with resonance frequency fres and I drive it with frequency fdrive, the spring will oscillate in a superposition of two frequencies, right? Which frequencies are they?
  44. G

    Synchro Signal Frequency changes

    Hi there! i have a question regarding signal and hope someone can help me out. Currently, i have a system that outputs synchro signal to other system. Apparently when the cables are connected to the system, the frequency of the synchro signal changes. From around 400KHz, it became around 1.2KHz...
  45. T

    Pulse repetition frequency ultrasound confusion

    Homework Statement Q:[/B]An ultrasound department seeks your advice regarding scans they perform to visualise and confirm foetal heart beating. They wish to know what imaging frame rate should be set in order to visualise the heart movement reliably but achieve the maximum possible reduction in...
  46. M

    Sources of Error in a Speed of Sound Experiment

    Homework Statement Determine sources of error which could have affected the results. Some background information: The lab consisted of playing a tone generated by a tone generator above a standing open-closed tube which had water in it. The first harmonic was measured through a computer system...
  47. S

    I Is there a frequency cutoff for Debye theory of capillary waves?

    I calculated the energy density of capillary waves with Debye method (pretty much Debye model in 2D), and I assumed there is a frequency cutoff for capillary waves as well. However, when I checked my work with solution I was quite surprised that the solution suggests there is no such a cuttoff...
  48. M

    MHB Calculate the rotational frequency in r/s and the diameter of the drive pulley

    a belt is driven by a pulley at 33m/s the pulley rotates at 750 r/min. calculate: (a) the rotational frequency in r/s (b) the diameter of the drive pulley
  49. T

    Wall thickness vs frequency.... sound isolation

    When sound hits a wall,part of it gets reflected and part of it gets transmitted due to acoustic impedance difference between solid and air. My problem,and point of this question is that having material or gas impedance number is completely useless unless we know the frequency and wall...
  50. J

    Ripple frequency of three phase half bridge converter

    Homework Statement Homework Equations Three phase half controlled bridge rectifier can have 3 pules at output or 6 pulses depending on firing angle. The Attempt at a Solution Ripple frequency is m times the input frequency where m is number of pulses. It can be 3 or 6. So why have they...
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