# 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.

View More On Wikipedia.org
1. ### I Why is Photon Energy Quantized in Terms of Sine Wave Frequency?

Hello everyone, I've been grappling with a concept for years, diving into internet resources and pestering professors, yet I still find myself tangled in confusion. I'm reaching out in hopes that someone here can shed light on a question that has been haunting my thoughts regarding the nature...
2. ### Comp Sci Use a simulator to produce a resonance curve for this RLC circuit

my issue here is what would i put in for frequency ? unless i use the formula to find the resonance frequency i have only used multisim live and you cant put in Vs 10 +j20
3. ### I Relationship between frequency and power for sound?

Hello, I have a problem wrapping my head around the relationship between frequency, power/pressure, and displacement. Let's say I have two sine waves that I generated in my computer: A 50 Hz tone and a 100 Hz tone. Let's say they both have an amplitude of 1. Therefore, they will both have...
4. ### Why is there are precession frequency here?

so I need to use the eq.: omega_pr = ##mgr / L_s## with r = 6cm. But from how I imagine/see it, the rod pierces the disk through the middle so how does this create precession if the weight will not cause a torque then and thus a hortizontal change in angular momentum? Thanks in advance!
5. ### I Normal vs angular frequency

This might be silly, but I am a bit confused by the conventions used for transitions in atoms/molecules. Usually these are given in nm and using the formula ##\lambda = c/\nu##, from here we can get the normal frequency ##\nu## and the angular frequency would be given by ##\omega = 2\pi\nu##. In...
6. ### Moving Source, Observer at Rest, derivation for Doppler effect

For this, Does someone please know whether they assume for the equation highlighted that ##\frac{v}{f} ≥ \frac{v_S}{f}## since otherwise the wavelength would be negative (which I assume is impossible)? Many thanks!
7. ### B To measure light's frequency, do we interact with each crest + trough?

How are we interacting with light to measure its frequency? And how'd we learn the distance between its crests and troughs? What sort of interactions are giving us such info?
8. ### I Mass of Electron & Flipping Frequency: Leonard Susskind Explains

According to Leonard Susskind, i.e. the electron has periodically interactions with the Higgs field condensate, that change the electron alternately to be right-handed an left-handed. At 44:20 in the video he says, that, according to the Dirac theory, the mass of the electron is proportional to...
9. ### Engineering Short vs Open Circuit: Is That Correct?

For the first circuit, Req = ZL + ZC = -j/(w*C) + j*w*L = 0 for short circuit, so w = 0? For the open circuit case, -j/(w*C) + j*w*L = infinity, so w = infinity? Is that correct?
10. ### Definition of angular frequency in nuclear structure

Hi all I am a little bit confused about the definition of angular frequency in the context of nuclear rotation, some times its defined in the regular way as $$E=\hbar \omega$$ and other time from the rigid rotor formula $$E=\frac{\hbar^{2}}{2I} J(J+1)$$ where ##I## is the moment of inertia...
11. ### I Does an electron have a quantum phase frequency?

Stationary solutions to the Schrödinger equation factor into a spatial part, e.g. atomic and molecular orbitals, and a temporal part that gives the phase rotation frequency. It is often assumed that adding a constant to the potential leaves the physics unchanged. And clearly, any "spectroscopic"...
12. ### Frequency selective surface radome

So I was reading about frequency selective surface radome, basically this is the kind of cover over the antenna which allow a certain frequency wave to pass through and reflect wave at any other frequencies. What I don't understand is the reflection vs transmission coefficient chart. So as I...
13. ### High power RF amplifier at fixed frequency

Hello! I have a signal at fixed frequency of 4 MHz and amplitude of 0.075 V. I need to amplify it to ~75 V with the same frequency. I checked online a bit and I found either cheap amplifier that can't amplify this much, or very expensive ones that (almost) can (I might need to use a smaller...
14. ### B Is there a fractional frequency of light?

If emw spectrum is continuous, possible wavelengths should be infinite and there should be fraction of frequencies like 25,2 hertz. Well is there a fractional frequency of light? In high school when we are teaching interference of light we say "only the same wavelength of lights interfere with...
15. ### I Relationship between the Different Frequency vs Decibel Graph Peaks

In the popular answer for the coin-mass question of Physics Stack Exchange, I am wondering what are the correlation between the first red peak at around 9kHz and the second red peak at 16kHz. I first thought that they are consecutive harmonics but there was no way of proving it as I do not know...
16. ### Formula for Resonant Frequency of 2 Metal Coaxial Cylinders?

Consider an LC circuit consisting of a parallel plate capacitor and a solenoid inductor in series. The formula for the resonant frequency of this circuit is 1/√(LC) where “L” is the inductance of the solenoid and “C” is the capacitance of the capacitor. Now consider a high-frequency cavity...
17. ### Intensity of a wave at half amplitude and twice frequency compared to a reference wave

TL;DR Summary: How do i find the intensity of this wave? I know I is proportional to amplitude / frequency squared, but I don't know what equation this comes from. And I don't know how to answer this.
18. ### Transformer frequency contradiction on induction heating

As a transformer freq bet higher, inside induction get more efficient i.e. less loss: 1. Hysteresis loss = η * Bmax^n * f * V. 2. Eddy current loss( proportional to B2mf2Bm2f2 ) Now it seems that losses increases with increase in efficiency... But the above equations are valid when max...
19. ### I Frequency of prime number gaps according to (p-1)/(p-2)

Caution I'm not a mathematician. In short, long time ago I calculated prime number gaps just for fun expecting an almost uniform distribution of the frequency of the gaps 2, 4, 6, ... . Instead the frequency showed a series of maxima and minima and I was confused. Later Professor emeritus Oskar...
20. ### Spring first natural frequency and hysteresis

Could anyone help me with some info on compression helical springs. First I would like to know if this type of spring would even have any appreciable histeresis when new, and if so does it does it grow with repeted use and age. I would also like to know if there is any relationship beteen the...
21. ### B Lowest frequency quanta seen

What is the lowest frequency/energy where photons have been observed? That is, electromagnetic waves observed as quanta, not continuous waves? Resolving noise that is not thermal noise, not shot noise from the discrete nature of the electrons in the receiving electronic, nor from the...
22. ### I Question about Waves -- "frequency" versus "angular frequency"

I've been reading many references that said "frequency" and "angular frequency" are two different things. I'm writing a report about damped oscillations experiments (that's a task from a subject in my college). Can someone tell me which one is the resonant frequency (natural frequency)? f or ω...
23. ### I'm getting two possible uncertainties for frequency

Calculate the speed and uncertainty in the speed for a wave with wavelength ##50\pm 3\mu s## and frequency ##30\pm 1kHz##. Also calculate the period and uncertainty in the period. I am not sure about my answer to the second part. I used propagation of errors to get ##\Delta...
24. ### Derive angular frequency for mass spring system

tried writing the x position as x = Acos(wt) (ignoring the phase) so that d2x / dt2 = -w2x Substituting that into the individual motion equations would get the required result for the individual masses, but I am not sure how to combine the equations to get the reduced mass
25. ### Wave Period Given Frequency

I think the answer is just 1/10 (according to the formula for period), so the answer is 0.1. Is that correct? Thanks!
26. ### Speed of Wave Problem

Since the period is 0.025s, I think the frequency is 1/0.025s = 40 Hz. I don't know how can I proceed solving the problem from here. I'm assuming I will have to try to find the velocity and wavelength, but idk how.
27. ### Simple Oscillation Question

I think I can solve the frequency by doing 1/0.400 μs, but I'm not sure.
28. ### Beat frequency heard from two tuning forks

Is my solution correct? I used v=lambda*f, i.e. f=v/lambda to get the frequency for each wave. Then I calculated the average of the frequencies to get 258Hz and found the beat frequency by doing f1-f2 to get 4Hz. I then said that this means the observer will hear a tone of frequency 258Hz which...
29. ### I Wave number, frequency, and velocity in dispersive waves

1) If I generate a dispersive wave, will it have well-defined constant wave number and frequency? Ones that don't change in time? 2) does the velocity of any point on the wave stay constant in time? 3) How does force interact with waves? Does a free wave act in analogy with free particles...
30. ### A Realizing EIT with Pulsed Laser: Intensity, Duration & Frequency

I have realized EIT with continuous laser. What are the requirements for the intensity, duration and repetition frequency if EIT is realized with pulsed laser? you can attach any reference:biggrin:thanks a lot!
31. ### Converting centrifugal acceleration to frequency

I've calculated this. Is it correct? a=ω²R => ω=√(a/R) T(period)=1/ω=1 / (√(a/R)) f = 1/T = √(a/R) [ if a=10G=100 m/s² ; R=1m ] then: f = √(a/R) = √(100/1) = 10 hertz In angular velocity, can I just convert a=ω²R to ω=√(a/R) and write instead of ω=(2π)/T (in the first line)?
32. ### B High Frequency Photons: More Mass, More Bend?

Since high frequency photons have more relativistic mass, should we expect them to bend more than lower frequency lights when traveling through a gravitational field, thus produce a rainbow effect? But we don't seem to experience rainbow effects with star light.
33. ### B Is it possible to get the photoelectric effect in red color frequency?

Is it possible to get the photoelectric effect in red color frequency?
34. ### Choosing a pulse capacitor, ESR vs reactance at frequency

While going through the catalogues I started to wonder, typically lower ESR caps cost more, but if I need the cap for DC smoothing , to filter out unwanted AC ripple, then I put that cap across my DC rails +-. Now so far so good. It's ability to filter out the AC ripple will be directly related...
35. ### Automotive Amplitude based frequency response simulation in Abaqus

Hi, I have inputs like displacement of a driving mechanism and then the frequency of concern . Displacement: 0.2 mm Concerned Frequency: 100 Hz I would like to evaluate a part with the input displacement applied to a node and not as base excitation. It can be sweep over the frequency range...
36. ### I Doppler effect and frequency

Hello everyone! I'm watching a Walter Lewin lecture and it seems to me at least that he is dividing maximum frequency of the sound by sound frequency of the transmitter to derive velocity of the transmitter, does this work? It seems that quantity would be dimensionless and velocity obviously...
37. ### I Error tolerant normal mode frequency

If a Hookean spring-mass system is made from one mass and a spring, to produce a system with a particular oscillation frequency, it's not a problem to use the propagation of errors concept to find how this frequency responds to small errors in the mass and spring constant. If a chain of...

39. ### I Phase velocity and frequency of a matter wave

The relationships for matter waves are (see e.g. https://en.wikipedia.org/wiki/Matter_wave): λ = h / p and E = h f, where E = m c2 From this the phase velocity can be derived and we get vph = c2 / v. v is the group velocity, which is also the velocity of the particle. If I consider these...
40. ### Finding the Frequency Domain and Time Domain magnetic field

I was wondering if anyone could walk me though a better explanation on how to get the given results for these two questions. The solutions posted by my professor aren't really clear to me so if anyone is able to better explain how to get the solution it would be much appreciated!
41. ### Angular frequency of a mass performing SHM

When given a small displacement ##x##, the equation for m is: (i) N sin θ = m.a where N is the normal force acting on the ball and θ is angle of the ball with respect to vertical. (ii) N cos θ = m.g So: $$\tan \theta = \frac a g$$ \frac x R = \frac{\omega^{2} x}{g} \rightarrow \omega = \sqrt...
42. ### Engineering Half-power cut-off frequency and frequency and phase response.

I have been given the attached following question: FIGURE 2 shows the response of a first-order filter to a step input. Estimate the half-power cut-off frequency of the filter and sketch its frequency and phase response. I believe that I have correctly calculated the half-power cut-off...
43. ### I Deriving Doppler Effect Frequency w/ Stationary Person & Moving Source

Can you derive the formula for frequency observed from doppler effect with stationary person and moving sound source away from the person like this: ##v_t = v + v_s## where ##v_t## is the total velocity observed by stationary person from moving sound, v is velocity of sound and ##v_s## is...
44. ### B Frequency of Gravitational Waves: Limit & Possibilities

A question elsewhere got me thinking about the frequencies/wavelengths of gravitational waves. The most obvious source of gravitational waves we are finding is from merging black holes, so presumably the orbital period will directly determine the frequency of those waves, yes? So the...
45. ### Spectral Intensity Formula by Using Frequency

I found there is kind of solution in Pointon's book: An Introduction to Statistical Physics for Students. But I don't know how to find intensity by using frequency.
46. ### Frequency Response Problem for given system

Hello, I am given an exercise in which I need to answer some questions, for this given system : y(n)=1/3[x(n)+x(n-1)] 1/ find the impulse response h(n), then H(n) 2/ calculate the magnitude ||H(n)|| and tell the nature of the filter 3/ calculate Fc which is cutoff frequency when Fe=8Khz , and...
47. ### I Sound Frequency & Pipe Wall Thickness

We have 2 open metal tubes, made of Stainless Steel. They both are the same length of 1 metre, and and Outer Diameter of 76mm. One pipe has a wall thickness of 1.5mm, and the other has a wall thickness of 2.0mm. It was our reasonable guess that the tube with 2.0mm wall thickness, should...
48. ### B Question about electromagnetic waves -- Penetration vs. Frequency

I read in a book that high frequency electromagnetic waves are more able to penetrate than low ones , so why radio waves can penetrate walls when light cannot?
49. ### Same frequency sounding different

I was always thinking that frequency decides the type of sound we hear ( ex: high pitched squeaky sound). But then I read somewhere that loudness i.e. intensity can also affect the sound we hear. Still the quality of sound should depend only on frequency since loudness would simply make it more...
50. ### Frequency of Oscillations of a Bead Resting on a Gas

Hi, this is a question from my textbook that I can't quite make sense of. I don't really know where even to begin, to be honest. The only thing I can think of is that the bead is at equilibrium, thus the force of gravity is equal to the pressure exerted by the gas. I don't know where the heat...