Frequency Definition and 1000 Threads

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. 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...
  2. 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...
  3. 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...
  4. 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...
  5. 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...
  6. 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.
  7. 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...
  8. C

    What is the frequency of wire oscillations with a pellet placed in the middle?

    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...
  9. 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
  10. G

    Is collsional frequency actually frequency per an electron?

    Hello. The collisional frequency is generally expressed by ν = nt×average of (σv), where nt, σ and v are density of target (atoms or molecules), collisional cross section of target and kinetic velocity of incident particles. σ depends on kinetic energy of incident particles I thought...
  11. J

    Relationship between frequency, wavelength, and speed

    Hi there, I am in need of another's thoughts on this topic. I at first thought frequency is something that doesn't change and is inherent to the source, so then increasing the wavelength shouldn't lead to an increase in frequency, but an increase in speed. I realized later that this only...
  12. S

    Bouncing ball and Doppler effect

    Homework Statement Consider two parallel walls perfectly reflective placed at the distance ##d = 0.8 m ##. A ball, provided with a device through which are emitted continuously frequency sound waves equal to ##f_0=430 Hz##, is launched from one wall to another. It moves with constant velocity...
  13. G

    Low PAPR permformance for Monochromatic Frequency signals

    I understand what is Monochromatic frequency signals from https://www.physicsforums.com/threads/monochromatic-waves.570958/, but could somebody kindly give a brief explanation about "why does a monochromatic frequency signal result in poor PAPR (Peak to average Power Ratio) performance"...
  14. Y

    Distance needed to walk in order to hear local maximum

    Homework Statement A person stands in an open space listening to the sound from two speakers. The speakers generate sound with a frequency of 489.5 Hz, the speed of sound in air is 343 m/s. The speakers are 2.00 m apart and the person walks away from one of the speakers along a line that is...
  15. Nile Anderson

    Determining the Wavelength of Sound using Resonance Tube

    Homework Statement [/B]Homework Equations I honestly do not know any relevant equations for this relationship. Well except f=v/2l. The Attempt at a Solution The only thing I could assume that it was was some sort of error , but I cannot find much material on the topic , so I was hoping to get...
  16. LLT71

    Higher frequency => higher energy

    can someone explain why high frequency waves contain higher energy? thanks!
  17. K

    B How Many Layers of Aluminum Foil Are Needed for a Resonant Cavity?

    I want to build a Resonant Cavity to play with frequencies around 100-700 mhz. I'd like to try different shapes, so I was thinking in using a cheap malleable material like aluminum foil. Questions: - I think one layer of aluminum foil might be too thin.. If I paste a couple of layers will do...
  18. W

    B Simple probability with high frequency

    I'm trying to remember simple probability form high school. I'd like to know how the probability of anyone event changes with frequency. So for example the probability of getting one ace of spades is 1/52; what is the probability of getting at least one ace of spades if the card is put back and...
  19. Sveral

    Choosing the Right Voltage Gain for Frequency Amplification | 250 Hz to 50 kHz

    How do I know, how big of a voltage gain for an amplifier do I need, if I want to increase the input frequency from 250 Hz to 50 kHz? Thank you.
  20. nnerik

    What is frequency from a photon's perspective?

    If a photon does not experience time, how can it change? Without change, how can it have frequency?
  21. ryanuser

    What is the Frequency of This Simple Harmonic Motion?

    Homework Statement A body performaning simple harmonic motion has a displacement x given by the equation x= 30 sin 50t, where t is the time in seconds. what is the frequency of the oscillation? Answers are: A. 0.020Hz B. 0.13Hz C. 8.0Hz D. 30Hz E. 50Hz (correct...
  22. MYMLA

    How Do You Calculate Modulation Index and Sideband Amplitudes in FM Synthesis?

    Homework Statement [/B] A pure tone (sine) carrier signal of 440 Hz is frequency modulated by another sine wave of frequency 440Hz with an amplitude of 1760. (a) For the steady-state portion of the output signal generated by synthesis above, calculate: i) the deviation and ii) the Index of...
  23. Geek007

    As the frequency increases so does the energy Em wave carry

    Hi everyone, As we move from left to right in EM spectrum the energy EM wave carries in creases as does the Frequency. Then why even after having a lot of energy waves can't penetrate hard me trials like rock. For example, Microwave aren't that good in penetration of tough objects but have...
  24. S

    Does Electric Field Strength Affect Field Emission Frequency and Current?

    Does the electric field strength required for field emission change with frequency? Better yet, at higher frequencies, is there a correlation with emission current?
  25. B

    Correcting Misconceptions about the Frequency of RF Pulses in MRI

    The magnetic moment of protons precesses at a frequency ω0=γB0 about the static magnetic field. In order to move the magnetisation vector into the transverse plane the RF pulse must be applied at a frequency ω0. However, as B1 (the field strength of the RF pulse) is << B1 how is this possible...
  26. S

    Resonant frequency in acoustics

    Hi, A question popped into my mind which I've never thought of in 20 years of making music: when you hold a tuning fork against a simple resonator (a guitar body, a table, any object with some volume really), the resonator amplifies the tuning fork's sound and you hear the tuning pitch louder...
  27. D

    A How to find vibrational frequency for specific bond? (DFT)

    Hello, I performed an optimization and frequency calculation at the ub3lyp 6-311g level of theory. The compound has the formula C39H41PS2. Using Molden, I am having a hard time identifying the frequency corresponding to the stretching of a phosphorus carbon double bond present in the molecule. I...
  28. M

    Over what frequency range are Maxwell's equations valid?

    Homework Statement I am studying for an Optics exam and in one of the practise tests is the following question: "Over what frequency range are Maxwell's equations valid?" Homework Equations Maxwell's Equations The Attempt at a Solution I've searched through my Griffiths Intro to...
  29. nmsurobert

    Beat Frequency of 2 Waves in Free Space

    Homework Statement Two waves of different wavelengths λ1= 1.5μm, λ2 = 1.63μm, are combined in free space Et = 1.5cos(k1x - ω1t) + 2cos(k2x -ω2t) Find the beat frequency Homework Equations (ω1- ω2) = 2ωm=beat frequency E02 = 4E012cos2(kmx - ωmt) The Attempt at a Solution I am quite stuck on...
  30. Z

    Formula relating thickness of pipe to fundamental frequency

    Homework Statement I understand how to find the resonant frequency of a closed pipe but when the thickness of the walls varies, the resonant frequency varies. Is there a formula that i can use to find the resonant frequency of a closed pipe given the length, temperature, speed of sound and...
  31. N

    Why frequency is more fundamental than wavelength?

    Please anyone explain that why frequency is more fundamental than wavelength inspire wavelength and frequency depend upon each other again frequency and wave number are also depends upon each other Then why we take the frequency as independent of wave number
  32. O

    How to record the frequency of a string using a phone

    I am currently conducting an experiment where I attach a string to a fixed end and run the other end over a pulley (assuming zero friction). A weight is tied to the end to create tension. We currently have length, mass per unit -length and tension, the only issue is measuring the frequency of...
  33. C

    Calculating frequency and wavelength in solution

    Homework Statement A laser beam is incident at an angle of 30.0° from the vertical onto a solution of corn syrup in water. The beam is refracted to 22.84° from the vertical. (a) What is the index of refraction of the corn syrup solution? I already got the answer of 1.29. (b) Assume that the...
  34. S

    Estimate vibrational frequency of N2 molecule

    Homework Statement Experimental data for the heat capacity of N2 as a function of temperature are provided. Estimate the frequency of vibration of the N2 molecule. Homework Equations Energy of harmonic oscillator = (n+1/2)ħω C=7/2kB Average molecular energy = C*T But this is an expression...
  35. reddvoid

    I Most effective of 1000 groups given mean median mode and N

    Hi, For a SoC project I am working on I need to select one cell which is most critical. example, If a bus is going through 1000 stops 1000 times I have mean median mode of delay contribution of that stop compared to the total delay to reach from start to stop point and N (number of times bus...
  36. O

    Why does changing the frequency of a wave affect the energy?

    I don't understand how changing the frequency of a wave effects the energy transferred to electrons following E=hf, but changing the intensity doesnt? Can someone explain it please, some sort of analogy or something?? THANKS!
  37. Z

    What is a method to find the fundamental frequency of a pipe

    Homework Statement How can i find the fundamental frequency of a closed piep (measuring cylinder) experimentally/ physicaly. I have done the maths and found the frequency but i want another way to prove this other than simply playing the calculated frequency back at the measuring cylinder. I...
  38. VonNathan

    Experiment to measure frequency of de Broglie waves

    Homework Statement Somebody knows an experiment to measure directly frequency of de Broglie waves?
  39. D

    Calculating the frequency response of filter with a matrix

    Homework Statement This is actually part 3 of the question. Part one was to form 7 equations to form a 7x7 matrix, part 2 was to solve it, which I've done. This question is to be done with Matlab, by the way. Part 3: Homework Equations Frequency response = Vout / Vin. The Attempt at a...
  40. dotsero

    Frequency Distribution Width & 'Rounding Up'

    Homework Statement I'm having trouble understanding setting up a frequency distribution. I am confident I am doing it right, but the book I'm using differs when calculating width. The problem gives a bunch of numbers representing the number of counties, divisions, or parishes for each of the...
  41. D

    B Photoelectric Effect under cutoff frequency

    I understand the concepts of photoelectric effect where an electron will be emitted when a photon with sufficient energy collides with it. There are two parts to this question, 1. What happens during the collision? Is the photon absorbed by the photoelectron wholly as energy? 2. If so...
  42. Tom MS

    I Resonant Frequency of an Atom in an Atomic Clock

    Beam standard atomic clocks work by changing the magnetic state of a cesium atom by applying a microwave frequency that matches the resonant frequency of a cesium atom. What is this resonant frequency of the atom in terms of actual events that occur on the atomic level...
  43. T

    Atmospheric Physics: Brunt Vaisala frequency question

    Homework Statement Gravity Waves. Consider a pattern of motion in which fluid elements move at an angle θ to the vertical. Show that for an atmosphere where the Brunt-Vaisala frequency is ωB the elements will oscillate with a frequency ν = N cos θ. Homework Equations , -Brunt Vaisala...
  44. Z

    Finding mass of an object on a spring, given Frequency

    Homework Statement A mass m at the end of a spring oscillates with a frequency of 0.84 Hz . When an additional 730 g mass is added to m, the frequency is 0.65 Hz . Homework Equations f*2pi = w w = (k/m)^1/2 f = (1/2pi)*(k/m)^1/2 The Attempt at a Solution I simply used the third equation...
  45. A

    I Frequency of a constant function

    Just a quick question that I feel should be simple, but I'm unable to come up with a satisfactory answer. A constant signal has an arbitrarily small period (rather, it has no fundamental period), and so it seems to me that this means the frequency of a constant signal grows without bound...
  46. G

    Automotive Load Spectrum and excited frequency

    Hi all! I have the following spectrum for a signal force: and this is a zoom in the range of interest: Can I state that this force is capable of exciting the natural frequency of the structure ( in the range 5-30Hz) or the force amplitude in this range is too low compared to the peak...
  47. B

    Calculating the Frequency of a Centrifuge in Hertz and Revolutions per Minute

    Homework Statement A research apparatus called a centrifuge undergoes a centripetal acceleration with a magnitude of 3.3x10^6m/s^2. The centrifuge has a radius of 8.4cm. Calculate the frequency of the centrifuge in hertz and in revolutions per minute. Ac=3.3x10^6,/s^2 r=0.084m Homework...
  48. A

    Managing X-Ray Hardness and Low Frequency Use in Tissue Analysis

    I got question in exam, 1) How to control hardness of X-ray? 2) why low frequency of x-ray is used for investigating tissue?? so in 1) what does controlling hardness means?? and in 2) can't we use high frequency of X-ray ?so that it will penetrate more as tissue are poor absorber...
  49. J

    Question regarding angular frequency of a SHM

    1. Homework Statement Homework Equations KE=½m(ωa)2 The Attempt at a Solution So first I did this: 2.4x10-3= ½ mω2(1.5x10-2)2 To find mω2=21.33 And substitute that into the KE eqn to find the new amplitude, which is 1.30x10-2 But I only did that because that was the only way I could think...
  50. Polkadot

    Smallest duration pulse frequency

    Homework Statement An electronic device is designed to amplify signals in the frequency range 80 MHz to 111 MHz. what is the smallest duration pulse in this frequency range that can be amplified without distortion? Homework Equations T=1/f The Attempt at a Solution the smallest duration...
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