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. K

    Natural frequency of pulley system

    Homework Statement https://www.physicsforums.com/attachments/197474 Homework Equations 3. The Attempt at a Solution [/B] ma + kx = 0 I know how to do it if the spring is in the middle of the pulley, not using energy method. by the free body diagram. But I am stuck at this. [Updated: I know...
  2. flamespirit919

    Frequency of Vibration of Two Masses Joined by a Spring

    Homework Statement Two masses ##m_1## and ##m_2## are joined by a spring of spring constant ##k##. Show that the frequency of vibration of these masses along the line connecting them is: $$\omega =\sqrt{\frac{k(m1+m2)}{m1m2}}$$ Homework Equations ##x(t)=Acos(\omega t)## ##\omega...
  3. whatphysics

    Amplitude spectrum vs frequency spectrum

    What is the difference between amplitude spectrum and frequency spectrum? In signals and systems.
  4. R

    MATLAB Frequency domain filtering in Matlab

    I am trying to implement several filters in Matlab for Fourier domain filtering. They are the cosine, Shepp-Logan, and Hann/Hamming window filters. These filters are defined as multiplying the ramp filter by the cosine function, sinc function, and Hann/Hamming windows respectively. This is how...
  5. jlmccart03

    Finding frequency of an AC current sin wave?

    Homework Statement An AC current is given by I= 475 sin( 9.43 t), with I in milliamperes and t in milliseconds. Find the frequency. Homework Equations w = 2pi*f The Attempt at a Solution I got 9.43/2pi which is 1.5 Hz, but that is wrong. I honestly have no idea what to do to find the Hz.
  6. W

    Get vibration frequency form absorption spectra line

    Homework Statement [/B] "Absorption spectra of gaeous HCl show a line at 3.5 μm which results form molecular vibration (oscillation from interatomic distance)" How do I get the frequency of vibration from this? Homework Equations ? If I knew this, then I could probably solve the problem The...
  7. J

    Frequency Division Multiplexing in Telephone

    "A standard FDM scheme for telephone signals is to multiplex 12 voice channels, each occupying 4kHz bandwidth, into a group signal with 48kHz. The next basic building block is the 60-channel supergroup, which is formed by frequency division multiplexing five group signals. The next level of the...
  8. Andre Teixeira

    I How to obtain the resonance frequencies of a given material?

    The frequency of plasma already achieved ... in a study, is presented the resonance frequency in eV, how to obtain in Hz? Wo = 7eV
  9. M

    Constant frequency of light and connection to QM

    Could someone provide a good explanation as to why light's frequency doesn't change under refraction? The textbook I'm using gave us a two step derivation and I don't really feel like it did a proper job in explaining anything (it's Haliday). Also, a slightly *crackpot* follow up question -...
  10. S

    Low Pass: Why did my professor use frequency and not angular frequency?

    Homework Statement We are given a passive RC low pass filter with an input voltage of 5 Vrms at a frequency of 1 kHz. The resistor has a value of 22 kΩ, the capacitor a value of 100 nF. There is a current i across the resistor. (see picture below) We are to calculate the magnitude and phase...
  11. R

    Determine the angular frequency of the system in SHM

    Homework Statement Determine the angular frequency of the system in the image. The cable is ideal but the pulley is not. I will present the same solution but with different coordinate axes. For some reason they arent the same and neither of them are correct. Given data: R is the radius of...
  12. Poetria

    Find Resonant Frequency of Spring-Mass-Dashpot System

    Homework Statement Consider the spring-mass-dashpot system driven by a sinusoidal force on the mass: (mD2+bD+k)x=F where sin(omega*t) Recall that for the unforced underdamped oscillator (b^2<4km, F=0), the value of the natural damped frequency omega_d=sqrt(k/m - b^2/(4m^2) Find the resonant...
  13. T

    Finding frequency components

    Homework Statement Which frequency components are present in the amplitude-modulated (AM) signal A(t)=[1+asin(2πfmt)]A0sin(2πfct), where fm= 3.5 kHz, fc = 540 kHz, and a = 0.1? Homework Equations A(t)=[1+M(t)]A0sin(2πfct), where modulating signal M(t) = sin(2πfm t + ∅), high frequency carrier...
  14. stevendaryl

    A Relative frequency and nonmeasurable sets

    There is a conceptual puzzle that I don't understand about nonmeasurable sets. Take the unit interval [0, 1] and let S be some subset. Now, generate (using a flat distribution) a sequence of reals in the interval: r_1, r_2, r_3, ... Then we can define the relative frequency up to n as follows...
  15. S

    Does frequency affect inductor and capacitor value

    Hi , I was measuring the inductor and capacitor value of a resistor bank with a 100Hz and 1kHz using a LCR meter by fluke. I realize that with different frequency, the L and C values were different. If the measured values were the inductance and capacitance I can understand that it changes...
  16. Conductivity

    Effect of frequency and intensity on PE

    if two light with different frequency have the same intensity then the PE current is the same. But that doesn't make sense, and some graphs show that if you increase frequency while intensity is constant, the current increases up to a point then drops. A couple of old threads, people mentioned...
  17. S

    SN diagram vs. Cycle Frequency

    Hi, What is the effect of the load cycle frequency on the SN curve (Wöhler curve)? Especially when the frequency matches the natural frequency of the component/material? Instinctively, I would think that at the natural frequency the number of load cycles until fracture is lower than at any...
  18. S

    AC Current in GHz Frequency and Zero Resistance

    Hello Experts, I am a physics newbie with big ideas. I have a question. I am thinking about how to produce a zero Resistance Current. We know we can do this using super-conductors in sub zero temperature, but maybe there's another way. My assumptions (which could be wrong): 1) Resistance in a...
  19. C

    Open Circuit Termination for Waveguides in High Frequency Labs

    Hi everyone, I am trying to understand that why do we use open circuit terminator for wave guides or any RF element such as coupler and etc. I know if we just leave it open, it does not work as open circuit. But why?
  20. R

    Finding wavelength and fundamental frequency with string

    The length of a string is 1328 cm. It is held fixed at each end. The string vibrates in eight sections; i.e., the string has eight antinodes, and the string vibrates at 97 Hz. Find the wavelength and fundamental frequency. I have no clue, anything helps! Thank you!
  21. R

    A Converting Partial Differential Equations to Frequency Domain

    Hello All, I would like to convert a partial diff equation in time domain into frequency domain, however there is a term of the form: Re(∇(E1.E2*) exp(j[ω][/0]t)) where E1 and E2 are the magnitudes of the electric field and [ω][/0] is the angular frequency. Can someone please help me to...
  22. Theudius

    Does Frequency Change in a Medium?

    Hi I was told by physics lecturer that both the wave speed and wave length of light changes when it enters a medium, however I questioned this stating that if both wave speed and wave length changed then frequency must also according to the formula c = fλ. He stated that "frequency is energy...
  23. T

    SHM Amplitude vs. Frequency graph

    Homework Statement A metal hangs vertically from one end of a spring. The other end of the spring is tied to a thread that passes over a pulley and is attached to a vibrator, as shown in the figure. The vibrator is now switched on. The frequency of vibration is varied from 0.7f to 1.3f where...
  24. T

    Finding the angular frequency of an object

    Homework Statement An object undergoes simple harmonic motion along an x-axis with a period of 0.50s and amplitude of 29mm. Its position is x = 12mm when t = 0s. Determine the value of ω in the equation of motion. Suppose that ω > 0. Homework Equations $$ω = \frac {2π} {T}$$ The Attempt at...
  25. V

    MHB Flood Frequency & Return Interval: 100-Year Analysis

    if in 100 years of records you have had floods in five of those years is the flood frequency 5 per 100 years ? and would the flood return interval be every 20 years?
  26. S

    Block on Spring SHM, Finding angular frequency

    Homework Statement An "ideal" spring with spring constant 0.45 N/m is attached to a block with mass 0.9 kg on one end and a vertical wall on the other. The floor has negligible friction, and you give the block a push and then let go. You observe that the block undergoes simple harmonic motion...
  27. H

    Natural Frequency for torsional vibration

    I am trying to calculate natural frequency for torsional vibration of fixed fixed beam using following formula. =1/2*3.142 sqrt(K*g/mr^2) hz Where K=J*G/L and G=Modulus of rigidity g=acceleration due to gravity=386.4 in/se2 m=mass hanging on the beam at distance 'r' from the longitudenal...
  28. T

    Sound & Music, String Frequency

    Homework Statement Suppose a string is 0.50 m long, it has a mass per unit length of 1.2 g/m, and it is under a tension of 52 N. What is the frequency of the second mode of this string? Express your answer in the SI unit for frequency? Homework Equations f = Vs/2L Vs = sqrt (F/μ) The Attempt...
  29. D

    Problem Related to Beat Frequency of a hollow tube

    Homework Statement Q. A hollow metallic tube closed at one end produces resonance with a tuning fork of frequency n at temperature T. The temperature of the tube is increased by dT. If the coefficient of thermal expansion of the tube metal is alpha, the beat frequency will be - (there are 4...
  30. L

    Does anybody know the sampling frequency of a cop radar?

    More specifically, does anybody know the sampling frequency of a mounted 360 degree cop radar? NOT a conical/directional hand-held radar gun.
  31. J

    Wavelength and Frequency in a Waveguide

    The problem states that the wavelength and frequency in a waveguide are related by: ##\lambda = \frac{c}{\sqrt{f^2 - f_0^2}}## then asks to express the group velocity ##v_g## in terms of c and the phase velocity ##v_p = \lambda f## Solution: Given that ##\omega = 2\pi f##, ## \omega(k) =...
  32. T

    Sound & Music - Ptolemy Reduced Frequency

    Homework Statement This is a homely. We were instructed to make a monochord and find and mark C5, G4, F4, E4, D4 & C4 by multiplying our starting length with the length rations (C5 = 1/2, G4 = 2/3, F4 = 3/4, E4 = 4/5, D4 = 8/9, C4 = 1) Then we used "Ravenlite" the application to measure the...
  33. Cocoleia

    Frequency domain and mesh currents

    Homework Statement Homework EquationsThe Attempt at a Solution So far I was able to transform each element into the frequency domain: I am just unsure how to work with the dots to find the mesh currents. Can someone explain? Thanks.
  34. C

    Determine the natural frequency

    Homework Statement Determine the natural frequency in Hz of the system sketched below given the following values: Mass m=4kg Spring stiffness k=28kN/m Length a=121mm Length b=93mm Homework Equations ω=(k/m)^0.5 The Attempt at a Solution so probably I need to find m should I multiply...
  35. Nikhil N

    EMI(Electro Magnetic Interference) Magnitude and Frequency

    I want to analyze the efficiency of my data communication between slaves and master in the presence of interference. The protocol what I am using is modbus, with baud rate of 9600 , I am using 1000 ft cable. What I am struggling to do is, how to couple the noise into the cable in a way it is...
  36. D

    Natural frequency of an Oscillating water column device

    Homework Statement Assuming that an OWC device is floating/moored in monochromatic waves. When there isn't air pressure distribution inside (atmospheric condition) the device behaves as an undambed body (with the oscillating chamber open to the atmosphere). When there is air pressure...
  37. Jordan ray

    Varying frequency of an LED drive circuit

    Greetings. How would I go about finding a way to use an audio signals frequencies to control the positive connection on a 12v dc led circuit? In other words, have the visual effects you get hooking up a dc led strip to an amplifier, but instead controlling the dc positive output to the strip...
  38. T

    A Investigating Velocity & Frequency Widths of Megamasers

    I was going through http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?2001ASPC..249..639B&defaultprint=YES&filetype=.pdf where the velocity of the maser is on the order of 80 000 km/s due to cosmic expansion (z = 0.265). But as you may see in Figure 1, the velocity width of the...
  39. mccoy1

    I The absolute value of the frequency in quantum mechanics

    I was reading Bransden's Quantum Mechanics 2nd edition, chapter 2 page 61. There,it says "It should be noted that since E =hv (v for nu), the absolute value of the frequency has no physical significance in Quantum mechanics..." Why is that? Isn't this a contradiction?
  40. W

    Doppler effect with frequency ratio

    Homework Statement An avant-garde composer wants to use the Doppler effect in his new opera. As the soprano sings, he wants a large bat to fly toward her from the back of the stage. The bat will be outfitted with a microphone to pick up the singer's voice and a loudspeaker to rebroadcast the...
  41. ntran26

    Question about an LTI System and its Frequency Response

    Hello All, I am trying to learn about lti systems and what not for my research work but before I can apply my research I have to understand the fundamentals, which is what this question is kind of about! I want to find h(t), the impulse response of an LTI system where my input and output are...
  42. P

    Angular Frequency of a Piston with Ideal Gas

    Homework Statement A frictionless piston of mass m is a precise fit in the vertical cylindrical neck of a large container of volume V. The container is filled with an ideal gas and there is a vacuum above the piston. The cross-sectional area of the neck is A. Assuming that the pressure and...
  43. jegues

    Determining the Fundamental Frequency Component

    Suppose you periodically receive samples of a periodic waveform at fixed instances in time Δt. It is known ahead of time that the periodic waveform will have a fundamental frequency component of 50Hz or 60Hz, but perhaps with some higher order harmonics present. What is the easiest way to go...
  44. jwkhjang

    What's the relationship btw frequency, wavelength, and temp?

    I'm currently studying wavelength and frequency and I've learned about the equation v= f*Lambda. What will happen if temperature is changed? I know that speed of the sound will increase. Does it mean that wavelength will also increase? I was curious because if temp. increases, the frequency...
  45. TheSodesa

    Amplitude and phase spectra from fundamental frequency?

    Homework Statement Let \begin{equation*} f(t) = 2 + \cos\left( 3t - \frac{\pi}{6} \right) + \frac{1}{4}\cos\left( \frac{1}{2}t + \frac{\pi}{3} \right) + \sin^2(t) \end{equation*} Determine the period ##T## and fundamental frequency ##\omega_0## of ##f## and draw images of its amplitude and...
  46. K_Physics

    Standing Waves On Strings: Harmonic and Frequency Problem

    Homework Statement String A is stretched between two clamps separated by distance L. String B, with the same linear density and under the same tension as string A. String B is stretched between two clamps separated by distance 4L. Consider the first eight harmonics of string B. For which of...
  47. M

    Measuring Frequency of an EMF with Gaussmeter: An Inquiry

    Hello, I got two series connected coils which I exited with 15 V AC. I got EMF between the space in the field and I measured it with gaussmeter saying 200 µT. I want to know the freqency of that generated electromagnetic field? Does anyone know how to do it? Is there any Equation for it...
  48. TheSodesa

    The period, angular frequency of a piecewise function

    Homework Statement The function ##f## is defined as follows: \begin{equation*} f(t) = \begin{cases} 1, \text{ when } 2k < t < (2k+1),\\ 0, \text{ when } t = k,\\ 2, \text{ when } (2k-1) < t < 2k, & k \in \mathbb{Z}\\ \end{cases} \end{equation*} What is the period ##T## of the function ##f##...
  49. S

    Finding frequency of a specific mechanical oscillator -- horizontal rod on pivot

    Homework Statement There is a cyllinder with radius 0.5 m fixed on the wall. We put a 6 metres long thin rod with mass 0.3 kg on it, which does not slip. I would like to calculate the oscillating time. It is a part of a clock, so the oscillating time is probably 1 or 2 seconds, but I got...
  50. harini07

    A question about wave motion and beat frequency

    Homework Statement 3 tuning forks of frequencies 200, 203, 207 Hz are sounded together.find out the beat frequency. Homework Equations Beat frequency= n1-n2 (n=frequency). The Attempt at a Solution I know that beat frequency is the difference in the frequencies of two superposing notes. But...
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