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. S

    Why didn't I see a peak at half the frequency in my FFT analysis of two waves?

    I am carrying out FFT analysis to compare two waves. One looks very much like a sine wave the other has an extra dip occurring at half the frequency of the main wave. I have been thinking around how I might expect this to show up in the FFT analysis. At first i was expecting to see a smaller...
  2. P

    Kalman filter with mixed frequency

    Hi first post hoping for some advise or guidance. Let's say I have GPS data on a robot every 10 Hz (every 0.1 second), I have accelerometer data every 40 Hz and steering wheel data every 80 Hz. I would like to use Kalman filter to produce estimates of where the robot is every 40 Hz given the...
  3. G

    Molecules With Radio Emission Under Current

    I am working on a project, however I am having trouble finding the right material for it to work. I am looking for a nano-material or any molecule that will emit a radio frequency when subjected to a voltage or a current at around 37 degrees Celsius. I would really appreciate it if someone could...
  4. E

    RLC Circuit Frequencies Help

    Homework Statement In each of the four circuits shown, an AC input voltage, ##V_0 cos(\omega t)## is applied on the left and the output voltage is measured on the right. Treat the input frequency as a...
  5. Q

    Frequency of Oscillation of a Block & Spring

    Homework Statement An oscillator consists of a block attached to a spring (k=400 N/m). At some time t, the position, velocity, and accelleration of the block are x = 0.100m, v = -13.6 m/s, a - 123 m/s2 A) Calculate the frequency of the oscillation for the system B)What is the mass of the...
  6. A

    Is There a Relationship Between Resistance and Frequency in Circuit Impedance?

    Hi everyone, I am trying to simulate a circuit containing resistors, inductors and capacitors. When i calculate the Impedance of the circuit i find it to be for example 150+100j for a frequency of 5Hz. When i run the same simulation for a frequency of 15 Hz i find it to be 162+134j. I understand...
  7. C

    Transmission Lines: Reflection Coefficient vs Frequency

    Hey guys - I've been using this website to study transmission lines. (great study aid - posting for others to use. Great for smith charts) However, I've noticed this graph they have for load matching: I'm having trouble finding or understanding a relationship for reflection vs frequency...
  8. neeraj kaira

    Relation of Bandwidth with the frequency

    I know they are directly proportional but how? could anyone explain it graphically ? thanks in advance
  9. F

    Determining angular frequency in an electric field using velocity.

    1. There are 2 negatively charged plates opposite each other. In between them, there is a vacuum tube (50 cm long), containing only 1 electron. Assume it is completely isolated. The charge value for the plates is equivalent to 10000 electrons. Initially the single electron is directly in the...
  10. L

    MHB Conditional combinatorics (by frequency of elements)

    Hey guys, I'd love to get the formula to answer the following question: I have 50 colorless balls and 100 different paints. All balls have to be painted. Note that the balls' order is not important and repetition is allowed (means I can paint up to 50 balls in any single color if I want). With...
  11. T

    Why do H2 and H2+ molecules have different vibrational frequencies?

    Homework Statement It's just that I am curious from the vibrational frequency table in the textbook--could someone tell/explain to me why H2 molecule's vib. frequency is about 4400cm-1, whereas H2+ is 2300cm-1? It just seems bizarre to me that such similar molecule should have different...
  12. D

    Pendulum Oscillation Frequency?

    Homework Statement Given a pendulum with fixed length, at what angle does the pendulum have to be released at in order to not follow the standard formula for frequency? Homework Equations P = 2pi*sqrt(l/g) The Attempt at a Solution I know that this equation holds for "small" angles (theta <...
  13. P

    Exploring Bohr's Model: Energy Levels & Frequency of Transitions

    Homework Statement In Bohr's model the allowed paths are those which the angular momentum is quantized by L=ħn and the electromagnetic radiation emission is only by transition through two of them ν=(Ei-Ef)/h. I am asked to use the above assumptions to calculate the energy levels and the...
  14. T

    Frequency and impulse response

    Hi, I have a discrete system with input x(t) and output y(t). Using the formula frequency response H(f) = y(f)/x(f) in the Fourier domain. Does this mean to find the frequency response I have to take the Fourier Transform of y(t) to get y(f) and divide it by the Fourier transform of x(t) ...
  15. A

    Simple Harmonic Motion and angular frequency

    Homework Statement A horizontal plank of mass m and length L is pivoted at one end. The plank's other end is supported by a spring of force constant k (see the figure below). The plank is displaced by a small angle θ from its horizontal equilibrium position and released. Find the angular...
  16. K

    How to determine the frequency of EM wave which does not oscillate?

    If I have a charge in a vacuum, and I accelerate it in a direction, then stop accelerating it, an EM wave will be produced for a short amount of time. How can you determine the frequency of the EM wave which is produced? Does it depend on the speed at which the charge moves? The amount the...
  17. R

    Frequency, transverse waves, low-pitch strings

    Homework Statement Two identical guitar strings are stretched with the same tension between supports that are not the same distance apart. The fundamental frequency of the higher-pitched string is 380Hz, and the speed of transverse waves in both wires is 200 m/s. How much longer is the...
  18. N

    Calculating the Frequency of White Light

    I am doing a research project on sonoluminescence and I want to measure the ratio between the frequency of the sound waves needed to create the cavitation bubble to the frequency of the light emitted. If I have the spectral lines of the light emitted, is there a way to measure the frequency of...
  19. Z

    What is the lower limit of frequency range of acoustic phonon modes?

    Good day everyone. I would like to know about the lower limit of the frequency range of active acoustic phonon modes. Textbooks say it can reach zero. But I am curious about whether it can be very small, such as 1 micro volt or the like. Would a phonon mode of so small energy be of any...
  20. T

    What is the tension of the string needed for a 440 Hz fundamental frequency?

    Homework Statement [/B] A violin string which is 30 cm long is tuned using a 440 Hz reference tone. A) What is the wavelength fundamental mode of the string? B) When the string has a tension of 34 N a violinist hears 5.7 beats per second. What are the frequencies at which the string might be...
  21. S

    What is the minimum frequency to keep the mass moving?

    Homework Statement A mass of 2.0 x 10^2 g is tied to a 1.6 m long string and spun in a vertical circle. What is the minimum frequency to keep the mass moving? Homework Equations Fc=m4(pie)rf^2 The Attempt at a Solution I know I have to use this equation and make it equal to another to find Fc...
  22. A

    How do I normalize angular frequency for circuit optimization?

    Hey all, This question may sound daft, but how do I normalize angular frequency? For a little background: I'm trying to optimize some circuits, and I've managed to write some successful code using the "Design of Ultra Wideband Antenna Matching Networks" book, but the code requires normalized...
  23. D

    Why is my op-amp frequency response not ideal?

    I am having a play about with the differential amplifier using a LM324 and have shorted both inputs and set them to 3V sine wave at 100Hz. i understand that in a ideal op-amp the output should be 0, how ever i am unsure of what is happening at the output... i increase the frequency every 1Khz...
  24. Chacabucogod

    Relation Between Electric Frequency and magnetic field rotation speed in a motor

    Hi! I understand that if you have a stator with a a three phase electric signal going into it, both the frqyency and angular velocity of the magnetic field and the electric entry will be the same. Now when you feed it with 2 groups of three phases electric signals you get four poles, or at least...
  25. G

    Measuring Light Frequency: Does Newton's Law Apply?

    Can anyone tell me if the following is correct? Traveling directly towards a source of light at some constant speed, we will measure its frequency to be higher (compared to rest frequency) than what we would expect when using Newton’s laws. Just as traveling away from the source, we would...
  26. R

    If time stops at the velocity of light, how can a photon oscillate with a frequency?

    If time stops at the velocity of light, how can a photon oscillate with a frequency? Frequency is defined with cycles/second.
  27. K

    Wavelength, speed and frequency question

    Homework Statement Typical AM radio wavelengths are about as long as a football field, while typical FM radio wavelengths are about a meter long. Which one has the highest frequency? If AM wavelength is 100 times longer than an FM radio wavelength, then how do the frequencies compare? How do...
  28. Z

    Optimal Frequency Homework: Maximizing Air/Ground Queues

    Homework Statement I want to apologize in advance as there are a few steps in this problem.[/B] 1.For each second, 2 planes join the air queue if randomAir1 < AirQueueThreshold and randomAir2 < AirQueueThreshold. 2. For each second, 1 plane joins a ground queue if randomGround <...
  29. T

    Determining Oscillator Frequency w/Feedback Capacitor

    I'm trying to determine the frequency of this oscillator . The traditional resonant frequency equation for the tank circuit doesn't give the correct answer as the feed back capacitor effects the circuit . i would also like to know what the feedback capacitor does? any help would be great.
  30. S

    CHI square independent test (small expected frequency)

    Homework Statement the expected frequency for the age of (21-30, 31-36, more than or equal to 37) for operation is less than 5 , so combination of these numbers are required for the expected frequency to be more than or equal to 5 . my question is which numbers should i combine? would my ans...
  31. C

    Why does photons of a given frequency satisfy the Boltzmann distribution?

    A mode of frequency ##\nu## has energy ##E_n = h \nu##. In terms of photons, the interpretation that I have read several places, is that this correspond to ##n## photons of energy ##h \nu##. Furthermore, it is stated that the probabilty of finding ##n## photons at frequency ##\nu## is given by...
  32. B

    Oscillation frequency of electrons in atoms (Bohr model)

    Homework Statement Here is a picture: http://puu.sh/bZtAu/82bdc201bc.png Homework Equations For force, F = (Ze^2)/4 * pi * e0 * R^3) * r f = sqrt(k/m) * 1/2pi Where e0 = vacuum permeability, 8.854 x 10^-12m and r = radius of hydrogen atom, 5.3 x 10^-11m The Attempt at a Solution I...
  33. Ryan_m_b

    Theoretical limit for data transfer given frequency

    Ages ago I read that the maximum possible bandwidth using radio waves was in the low tbps range. I've had this rattling around in my head ever since and have occasionally tried looking it up to see if it was true. I've not had much luck in that but it did prompt me to start wondering what the...
  34. T

    Calculating Oscillation Frequency and Max Acceleration of a String

    For the first part of the equation, I worked out k constant of a string which extended 12.6cm when a mass of 300g was suspended from it using the equation F = kx where F is the force applied and x its extension. So mg = xk, 300 x 9,81 = 0.126k, the answer was 23357N/m (23kN/m). The question...
  35. F

    Why isn't the frequency dependence of permittivity monotonic?

    I naively thought that most materials were transparent to radiation of frequencies above their plasma frequency, and opaque to radiation below it. The most intuitive (and analyzed lightly in Griffiths' E&M book) reason I've heard is that opaqueness is caused by electrons in the material...
  36. sweetdreams12

    Why isn't the light signal from a falling spaceship Doppler shifted?

    Just some conceptual ideas that I don't understand A spaceship starts falling under gravity with an acceleration g as measured by an observer Barry at rest on Earth. At the instant that the ship starts to fall, an astronaut Harry at the base of the rocket ship sends a light signal of frequency...
  37. D

    MHB Natural frequency of a crane dropping a car

    An electromagnet weighing \(3000\) lb is at rest while holding an automobile of weight \(2000\) lb in a junkyard. The electric current is turned off, and the automobile is dropped. Assuming that the crane and the supporting cable have an equivalent spring constant of \(10000\) lb/in, find the...
  38. EnchantedEggs

    Angular frequency versus normal frequency?

    Hi all, I'm struggling with the concept of angular frequency in the context of sinusoidal waves. We describe sinusoidal waves with equations like y(x,t) = Asin(kx-\omega t) , where \omega is the angular frequency, yes? But what does this quantity physically represent? The rate at which...
  39. E

    How to get valid frequency for a transfer function?

    Homework Statement transfer function: H(s) = 1/(s^2+s+1). question: compute half-power frequency Homework Equations none The Attempt at a Solution [/B]I got 4 answers: -0.605i, 0.065i, -1.169, 1.169 I know that only two of these are correct, one is 1.169 instead of -1.169 because frequency...
  40. S

    What is the correct frequency of the reflected ultrasound received by the bat?

    A bat uses ultrasound at 40kHz to locate a stationary insect. If bat is flying directly towards the insect at speed of 4m/s at what frequency does the bat receive the ultrasound reflections from the insect? Speed of sound = 340m/s. I went frequency = frequency of source x (velocity of...
  41. P

    Why does wave speed affect wavelength but not frequency?

    Hi! I was having some difficulty understanding this concept. If you know how many times per second a wave passes by a point (aka frequency) doesn't that basically say how fast it is? I understand how 2 waves, one with a short wavelength and one with a long wavelength can have the same speed...
  42. D

    MHB Natural frequency of a pendulum being lowered at 2m/s

    A heavy machine weighing \(9810\) N is being lowered vertically down by a winch at a uniform velocity of \(2\) m/s. The steel cable supporting the machine has a diameter of \(0.01\) m. The winch is suddenly stopped when the steel cable's length is \(20\) m. Find the period and amplitude of the...
  43. D

    MHB Find Spring Constant \(k\) & Mass \(m\) for Natural Frequency

    The natural frequency of a spring-mass system is found to be 2Hz. When an additional mass of 1kg is added to the original mass \(m\), the natural frequency is reduced to 1Hz. Find the spring constant \(k\) and mass \(m\). Since the natural frequency is 2Hz, we have that \(\omega_n = 4\pi =...
  44. R

    Exploring Voltage & Frequency Effects of AC Power Supply

    Explain the effects of AC power supply parameters-voltage and frequency?
  45. J

    Frequency for Vibration Modes of a Square Membrane

    So the equation to obtain the frequency of the modes of a square membrane is something like ω m,n = ∏ [(m/a)^2 + (n/b)^2]^(1/2) This equation can be used to get the frequency for Modes such as (2,1) and (1,2). How do I get the frequency for such modes as (2,1)+(1,2) and (2,1)-(1,2) ...
  46. anemone

    MHB Finding the Frequency of 5 in $S$

    Let $S=1+10+19+28+\cdots+10^{2013}$. How often does the digit 5 occur in $S$.
  47. CassiopeiaA

    Blackbody radiation over whole frequency spectrum

    I was studying black body radiation and how quantization of energy solves the problem of ultraviolet catastrophe. But I have a very fundamental doubt. A black body can be assumed as a cavity with a small hole with radiation leaking out of it. As the temperature of the black body is increased we...
  48. R

    Exersize related to sampling frequency of 2D signal

    For an image, higher the dimensions of image ,more is the resolution of the image.But is there any relation present between sampling frequency and dimensions of image? Also, Whether the Number of samples presents in an image is equal to product of dimensions of image?
  49. M

    Frequency or phase shift when using pulsed wave doppler

    Hi, I'm a medical student who is using ultrasound to measure cardiac strain. I'm trying to read up a bit on the physics behind doppler imaging (I did AP physics in high school), and I have a question for some genius out there. I keep reading that in pulsed wave doppler measurements, one does...
  50. N

    Linewidths - Frequency and Wavelength

    Hi, Probably a really stupid question... but I'm confused about how to relate a line width in frequency to one in wavelength. To me it seems obvious that if there's a broader spread of frequencies, there must be a broader spread of wavelengths, and vice versa - after all, the line is broader...
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