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. T

    What frequency did you hear 3 seconds after police pass?

    Homework Statement The police was headed to a felony and passed you so you stopped. What frequency did you hear 3 second after the police passed you? Homework Equations f=1/T The Attempt at a Solution f=1/3 f=.33Hz
  2. T

    What is the frequency of a police siren when you run away from it?

    Homework Statement Temperature is 28C, a police car with a siren blazing at 988Hz is coming toward you at 23m/s so you run away at 7m/s. Homework Equations f=f(v+-o/v+-s) The Attempt at a Solution I'm confuse on the formula.
  3. Stella.Physics

    Color of Light: Frequency vs Wavelength.

    So today I was thinking that color is connected with a given wavelength (for example red light in air is about 600nm) but after some research online I found out that color depends on the frequency and when light travels through various optical media (like air, glass etc) speed and wavelength...
  4. G

    What is the Uncertainty of Human Hearing Frequency?

    what can be the uncertainty of the frequency that humans can hear ? I'm aware that there are many ways,but i tried google-ing to find them but i couldnt. if you could help me it would be great.
  5. Z

    Resonance frequency of a wine glass experiment

    Homework Statement My group and i need to do an experiment for school. We decided to investigate the effect of water level in a vine glass (or volume) on the resonance frequency. Basically does the resonance frequency change when you change add water to the glass. I would just like some help...
  6. Geek007

    Bit rate, bit interval vs frequency, time period

    can we use frequency and time period terms for digital signals or we have to use bit rate and bit interval terms for digital signal. in simple words,
  7. Geek007

    Does the non-periodic signals have frequency or not?

    Can someone kindly explain , what is the frequency of non periodic signals? Periodic signals have frequency of number of cycles completed in one second and but non periodic signals don't have repeated pattern so what would be the frequency of non periodic signals. Kindly do explain it in simple...
  8. A

    Relationship among Intensity, Frequency, and Current

    Hi all, I am really confused about the relationship among these three properties and I cannot find an answer satisfying enough.. If frequency of incident light increases but intensity remains the same, the photocurrent will decrease. Does this mean that the new curve on the current vs. voltage...
  9. jedishrfu

    The Tacoma Bridge Collapse was Not due to Resonant Frequency

    An interesting article on the Tacoma Narrows Bridge collapse of 1940 shown to students of physics throughout the years as an example of the power of resonant frequencies. However, the explanation was much too simple to be true. Here's the real story...
  10. R

    I Do gravitational waves transmit energy in all cases?

    I was told that there are two kinds gravitational waves. One dies out as 1/r, another one dies out as 1/r^2. The former is what LIGO detected, the latter is not. While I trust the professional qualification of the person very much, as a non-physics professional, I would like to a second person...
  11. Divinite

    Find the third harmonic (Sound Physics)

    Question: The frequencies of the first three harmonics of a 300 Hz square wave are 300 Hz, 900 Hz, and 1500 Hz. If the amplitude of the fundamental is 1.00 A, then the amplitudes of the second harmonic is _____ A, and the amplitude of the third harmonic is _____ A. I found the answer to the...
  12. R

    Frequency of gears (given frequency of shaft)

    Homework Statement Homework Equations tangential velocity v = ωr angular velocity ω = 2πf The Attempt at a Solution Not really looking for help to solve the problem. I'm just confused about the speed/angular velocity and frequency If the frequency of the motor is given as 24 Hz, then...
  13. C

    Why does number of coils on primary affect frequency?

    I'm reading a guide on how Tesla coils and slayer exciters work on this Instructable and it was speaking about how to fine-tune the Tesla coil in order to match the resonant frequency of the secondary coil. I understood it when it spoke about changing number of capacitors or the distance of the...
  14. vetgirl1990

    Angular frequency of plank attached to spring

    Homework Statement A horizontal plank (mass 2kg, length 1m) is pivoted at one end. A spring (k=1000N/m) is attached at the other end. Find the angular frequency for small oscillations. Answer: ω=39rad/s Homework Equations ω = √(mgd + kΔxd/I) I think I would be treating the plank as a long...
  15. hiver

    Finding the value of g using 2nd Harmonic Frequency

    Homework Statement As the captain of the scientific team sent to Planet Physics, one of your tasks is to measure g. You have a long, thin wire labeled 1.80 g/m and a 1.30 kg weight. You have your accurate space cadet chronometer but, unfortunately, you seem to have forgotten a meter stick...
  16. C

    Frequency of Vibration of a water tank

    Homework Statement Assume that there is a tank on a 200 ft pedestal type support. When full the tank and contents have a weight of 50,000 lbs and it is never drained to a point where the tank and contents have a weight less than 20,000 lbs. Assume the pedestal weight is negligible compared to...
  17. SpicyWassabi101

    Solving Beat Frequency with Tuning Forks: f2 = f1 ± fb

    Homework Statement Tuning Fork A has frequency of 320 Hz. When it is sounded with Tuning Fork B, 14 beats are detected in 7.0 seconds. Elastic bands are placed on the tines of Tuning Fork B and the beat frequency drops down to 1.0 Hz. What was the original frequency of Tuning Fork B? Explain...
  18. C

    Find the frequency of the cylinder's vertical vibration

    Homework Statement Homework Equations w = √k/m w = 2π/P ƒ = 1/P The Attempt at a Solution I feel like I'm so close to the answer, I think it has something to do with the fact that there's a spring and pulley in the system that is throwing my answer off. I have √k/m = 2π/P So, P =...
  19. M

    How to derive Mersenne's fundamental frequency formula?

    I'm talking about equation 22, Does anyone know how to derive this? It's Marin Mersenne's formula for fundamental frequency, but I'm perplexed as to how he derived it. L would be the length, F would be force, and μ would be mass per unit length. f is the frequency Thanks
  20. D

    How to find the natural frequency in ansys apdl

    Hi! I am new in ansys. I am doing rotor dynamic study of a high speed rotating shaft. the shaft comprise of two discs and at the it ends the shaft is supported by the bearing I am facing problem in modelling stage please tell me how to model the bearing and disc briefly.I am uploading the image...
  21. Y

    Doppler effect train frequency question

    Homework Statement When a train running at a speed of 72 km/h approaches a crossing signal, a passenger in the train hears the siren at 720 Hz. What frequency does the passenger detect after the train passes the crossing signal? Take the speed of sound in air to be 340 m/s. Homework Equations...
  22. T

    How to graph the duffing frequency response

    I`ve been able to use excel to plot the trajectory of a harmonically driven duffing oscillator for arbitrary parameters using Runge-Kutta method. I would like to do the same thing for the frequency response, but I simply can not figure out how. I am not very mathematically advanced so the first...
  23. NPB777

    Variation of Frequency of sound underwater

    Hello, I am very much interested to how frequency of sound varies in water. Also, how the frequency varies with temperature and depth? What are the different formulas related to this? Secondly, how can we determine the best frequency of operation? I would be very thankful if anyone could answer...
  24. G

    Frequency of small oscillations

    Two bodies of mass m each are attached by a spring. This two body system rotates around a large mass M under gravity. Will there be any relation between frequency of oscillation of the two body system and frequency of rotation? Frequency of small oscillations of a single body rotating in an...
  25. Nineways

    Computing 'Sound' Frequency of a Planet: Possible Methods?

    Is there an accurate method in computing the 'sound' frquency of a planet? For example, taking the orbital path of say Jupiter for one year, and computing it into an audible frequency? I'm looking for ways to compute this, but I am at a loss to where the best starting point is. Could Bohr's or...
  26. Ethan Godden

    Frequency of a simple harmonic oscillator

    Homework Statement The problem is attached Homework Equations f=2π/ω=2π√(m/k) The Attempt at a Solution My idea is that the mass doubles resulting in a √2 increase in the equation above. However, apparently the answer is (c). I have a strong feeling the book answer is wrong, but I wanted to...
  27. Mr Davis 97

    Does the Doppler Effect Affect Wave Velocity in Moving Observers?

    Imagine that there is a stationary source that is propagating waves (such as sound waves). Let's say that the wave speed in the medium is 343 m/s. If I am an observer, and I begin to move towards the waves, will the wave speed increase due to the idea of relative velocities, or will only the...
  28. M

    Radiation - temperature - frequency

    Hi. Dunno if this makes much sense. If radiation is emitted from a star with a certain frequency, does that frequency change, if that radiation travels through areas of different temperatures?
  29. Captain1024

    Finding Impulse And Frequency Responses

    Homework Statement Consider a LTI system defined by the following difference equation: ##\mathrm{y}[n]=-2x[n]+4x[n-1]-2x[n-2]## a) Determine the impulse response of the system b) Determine the frequency response of the system Homework Equations DTFT...
  30. A

    The highest frequency of ac current?

    I heard about a research where ac current is generared in metal covered nanotubes exposed to visible light, the same way as it does in receiving tv antennas. Isn't there a limit to how quickly electrons can accelerate on a metal surface (because of inertia and maybe some extra factors) to...
  31. brainbaby

    Role of gain in amplifier's frequency compensation....

    Hey guys please help me on this... The text says that we have to alter the open loop gain in order to compensate an amplifier. The open loop gain should be reduced below unity before sufficient phase shift develop to cause oscillation in the amplifier at higher frequencies.. My question is why...
  32. P

    Waves on a string and frequency

    So I was reading our lecture notes about generalising the motion of a string by considering it as a system of N masses, and one of the arguments was that no matter where you are on the string, each mass element will oscillate with the same frequency. This makes intuitive sense for an ideal...
  33. G

    Piezoelectric strain rate and frequency of applied voltage

    If one were to apply, for example, 60 Hz AC to a piezoelectric material, would the strain rate be 60 Hz? I am not entirely sure if I am using "strain rate" in its proper sense; I use it merely to describe what I imagine would be the rate at which the material expands and contracts while exposed...
  34. E

    Field frequency and angle of incidence in optical waveguides

    Hello! In this previous post, most replies point out that it is not possible to predict the angle of refraction (and so the frequency) at a certain interface, given the wavelength of the original signal. In particular, But when dealing with optical waveguides, it seems to be different. I am...
  35. neilparker62

    Hydrogen 1s 3s transition frequency

    Good day With reference to the following article: https://hal.archives-ouvertes.fr/hal-00506468 The measured frequency is given as 2922742936.729(13)MHz but right at the end of the article, the following is written: "The hyperfine structure of the 1S level is well known and that of the 3S...
  36. Y

    Do we get 2x the frequency when doing P=VI for AC Circuits?

    I know that when you get a current from a voltage (like calculating current through resistor), the current and voltage equations have the same frequency. Does this still hold for power P = VI ? So assume V in Euler form, V(t) = Vcos(wt+theta) + jVsin(wt+theta) = V*ej(wt+theta) and in Phasor...
  37. M

    Human Body and Frequency detection

    Is the Human body capable of creating any type of frequency ? Of course vocally but beyond that ... . What devices are in existence that can measure or see frequencies of living things ? Have there been experiments with documented results that shows frequencies created by the human body ?
  38. U

    Questioning RF Frequency & Filters

    My question is about RF frequency... The RFs are electromegnetics waves...That means they are one type of Light waves... right?? The other question is about perticular frequency of RF signals...When we want to transmit or receive some perticular frequency... we tune our radio at that perticular...
  39. N

    MHB Solve for frequency & angle in dispersion equation

    OK I'm about to grow (more) gray hairs... Could some friendly soul smarter than myself kindly help me solve for both f and theta respectively in the following equation, please: x = sin[ (pi*f*W)/c * sin(theta) ] / [ (pi*f*W)/c * sin(theta) ] Getting stuck at "arcsin of arcsin" sort of...
  40. J

    Why does a black body radiate in all the frequency spectrum?

    I understand why a black body absorbs every frequency(it is the definition of a black body!) but i do not understand why it also radiates at all frequency spectrum.
  41. S

    Solving Physics Homework: Frequency Change

    Homework Statement A cord vibrates with a frequency of 3.0 Hz when a mass of 0.60kg is hung up from it. What is its frequency if only 0.38kg hangs from it? Homework Equations f= 1/2pi sqrt k/m The Attempt at a Solution 3.0= 1/2pi sqrt ( k/0.6) k=213.18 N/m f= 1/2pi sqrt (213.18/ 0.38) f=...
  42. N

    Frequency analysis of transistor amplifiers

    Hi guys, I am trying to do this question on my own but i am not confident if what i am doing is correct. please download the Question2.docx file and my workings are in blue. hope someone can help me with this. 1. Homework Statement A. For circuit (a) below, calculate: R_e and R_C to make...
  43. Y

    Add currents with same frequency but different phase?

    So assuming I1 = 1<10 and I2 = 2<20 And assume these current sources are in parallel, pointing in same direction. Can I say total current is I1 + I2 = 1<10 + 2<20 ? I would convert the phasor to complex number to combine them, but will this work?
  44. K

    Finding the frequency of a vibrating particle on a string?

    Homework Statement A particle of mass m is on a massless string of length 3a, which is held horizontally across with a tension T(which you can assume doesn't change with the small vibrations). The particle is a distance of a from one of the edges. Set up a diff. equation that describes the...
  45. N

    Do X-rays' wavelength or frequency help them not excite electons....

    ... to transmit through opaque objects.? So when it comes to bone the x-rays cannot pass through them, or the steel plate because, the energy is higher, and or those bones, and steel plate have more electrons in their shells, and so is it the more electrons that absorb the X-rays, or is it the...
  46. T

    Frequency problem (static equilibrium)

    Homework Statement The lower end of a uniform beam is attached to a vertical wall by a frictionless pivot. The beam extends away from the wall and upward, making a 62° angle with the wall, and it is held in place by a horizontal wire attached from its upper end to the wall. The wire's length...
  47. C

    MHB Frequency-realitive frequency and a histogram frequency

    I am having problems with creating a constructed frequency and realitive frequency distribution and converting it into a frequency chart. This is a list of the past 44 presidents inaguation ages from g. Washington up to barak Obama? 57 61 57 57 58 57 61 54 68 51 49 64 50 48 65 52 56 46 54 49 50...
  48. H

    Find frequency response and circular frequency

    Homework Statement We are given that system of 1st grade 1/2 * dy(t)/dt + y(t) = x(t) 1) We need to find frequency response { H(w) } 2) We need to find circular frequency -3dB 3) We need to find the absolute value of H(w) in dB for frequency f = 3/π Hz 2. Homework Equations (log is always...
  49. J

    Force/Torque frequency proportional to current frequency

    Lorentz force equation shows us that current is proportional to the force. Is it safe to assume that the force generated by an AC current at 60Hz will always have the same frequency? In other words, as the current increases and deceases (sinusoidal) the force will follow the same pattern at the...
  50. S

    Find wavelength, frequency and speed of a wave,

    So I was given this diagram to a wave of a rope. the following questions i have to answer... 1) Find the wavelength in metres. 2) If the time that the wave takes to move from point X to point Y is 6.0 s, determine the speed of the wave and its frequency 3)Find the speed and wavelength if the...
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