What is Frequencies: Definition and 411 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
Recent contents Top users
  1. D

    How Do You Calculate the 3dB Frequency for High and Low Pass Filters?

    Homework Statement (a) The input capacitor and the voltage divider network form another high pass filter. Calculate f3dB for the input high pass filter made with C = 4.7uF and the appropriate R value. (b) calculate the f3dB for the output pass filter made with C = 4.7uF and R = 100K...
  2. B

    Maximizing Your Sound System: Understanding FFT and Low Frequencies"

    so my fft is working for notes 8b-1G# so from 7902 Hz to 51.91 Hz after that it says 46.25 Hz is the same 49.00Hz : notes 1F# and 1G. it then says notes 1E and notes 1F are the same (41.20Hz, 43.65Hz) I am using this site : http://onlinetonegenerator.com/?freq=5000 to product the...
  3. T

    Do Standing Waves Occur for All Frequencies?

    Do all frequencies produce standing waves or just the harmonics? My physics textbook stated that standing waves are form when two wave trains with equal amplitude and frequency meet each other in opposite directions. Does the common frequency of the wave trains have to be one of the harmonics...
  4. B

    Music Note Frequencies: Research & Info

    I have been doing some research on music note frequencies. and I am getting a lot of mix information. ok middle C is 261.625565 hertz Human can sing between 150Hz to 4K Or between 60Hz to 2K ? Also I tried this site http://onlinetonegenerator.com/?freq=5000 and I can't hear 60Hz...
  5. N

    Smaller Antennas, Higher Frequencies: The Need for Size Reductions

    Why antenna needs to be smaller in size with higher frequencies (EM waves)? please
  6. T

    Phase cancellation with opposing and unequal audio frequencies.

    Greetings to ALL. tonequester here. I am re-doing my first, and LONG post. Concerning an electric guitar. Strings resonate at say, 800Hz. Wooden neck and body have their own resonant frequency, so I am told. No two guitars resonate at the same frequency, as no two, complex, combinations of...
  7. A

    Blue light and resonant frequencies

    Hello again! Just a few multiple choice questions. When blue light strikes an opaque object whose resonant frequency is the same as the frequency of the blue light what happens? ( Choose as many as apply) A) The amplitude of the vibrations of the electrons in the object becomes larger B) The...
  8. C

    Engineering RLC circuit with two angular frequencies

    A resistor, an inductor of inductance value of 0.02H and a capacitor are connected in series. When an alternating voltage of 200sin(1000t-10°) is applied to the series combination, the current flowing through the circuit is 20√2sin(2000t-20°). Determine the values of resistor and capacitor...
  9. Q

    Finding Period Of Voltage With Multiple Frequencies

    How do you solve questions of the type: Find the period of the voltage a) 3cos(2500t) + 4(7500t + pi/2) b) a generic waveform: a*cos(x*t)+b*cos(y*t + theta) I saw questions similar to the above while going through a book. I attempted such questions when I was in college, but don't...
  10. J

    Color Organ Filters: Bass/Mid/Treble Cutoff Freqs

    So I am making a color organ using my ipod, speakers, splitter, butterworth filters with gain for three separate frequencies. I want to have a low, mid, and high but I have no idea what the cutoff frequencies for each should be. I know we hear something like a band of 200 Hz to 20 kHz but I am...
  11. J

    Hardy-Weinberg: Understand Allele Frequencies & Genotype Freqs.

    Hello. I am having trouble getting a grasp around Hardy-Weinberg Allele Frequencies. I understand that p +q = 1 and that p= freq. of dominant allele whereas q= freq. of recessive allele. I understand that the next part was derived by squaring the equation above: p2+2pq + q2=1 However, I do...
  12. M

    Single beats, infinitely many frequencies

    Does anyone know how to prove that if we want to make a single wavepacket in space we necessarily have to superpose a continuous infinity of frequencies? Any help much appreciated!
  13. G

    Vibrational partition function - Calculate from several frequencies

    Hello everybody, I registered here hoping to finally find a fundated answer about what I by myself seem not be able to figure out. Question in short: We have calculated a list of wavenumbers for some molecular systems. How do you get the vibrational partition function from that? My...
  14. J

    Understanding the spectrum of frequencies

    What is the distinction between EM waves and Sound waves. I know that sound is cyclical vibrations in some sort of medium. When the frequency increases, do these vibrations become EM waves? I know that EM waves do not need a physical medium. But they are still energy, and sound is energy. So...
  15. D

    Forced Normal mode frequencies of 4 horizontal springs, 3 masses

    Homework Statement Hey guys. The title says it all pretty much. We need to find the normal mode frequencies of a driven/forced system containing 3 equal masses connected by 4 springs of equal spring constant k. Homework Equations F=m\ddot{x} Spring potential V = 0.5kx^{2}...
  16. S

    Frequencies of standing wave in pipe

    Homework Statement A speaker is placed near the open end of a 0.5m pipe (closed on the other end). what is the speed of sound if the pipe resonances at 600Hz for n=2? Homework Equations fn=(2n+1)*V/4L Or? fn=(2n-1)*V/4L The Attempt at a Solution I saw both versions of the...
  17. S

    Negative frequencies in spectrum analysis

    Negative frequencies in spectrum analysis... Hello everyone... When we do the frequency analysis of a signal using Fourier transform, we get spectrum at negative frequencies also. What are they and what is the physical significance of such frequencies? Its hard for me to imagine a negative...
  18. I

    Musical frequencies, harmonic or nonharmonic?

    Hello! I have this general question regarding (musical) frequencies: I'm having a bit of a hard time putting what makes logical sense to me, as opposed to what I'm being taught in school. My teacher is basically saying the following: If the fraction/division of two frequencies is rational, the...
  19. T

    What happens if i apply different AC frequencies into a motor?

    so let's say i have a motor and two sinusodial AC power supplies. they both have different frequencies but the same voltage. i apply both of them into the induction motor. what will happen in terms of speed or anything else which can affect the motor's performance?
  20. V

    Antenna Design Filtering Out UnWanted Frequencies

    Hello. I was wondering if someone could explain to someone with no electrical engineering background where would one place the resonator whose sole responsibility is to amplify sine waves at a particular frequency while ignoring other sine waves. Would this resonator be located by the antenna...
  21. C

    Refractive Index of Gold at Microwave Frequencies

    Hi, can anyone help me out with the refractive index of pure gold at microwave freguencies? (Specifically something close to 2.4 GHz, or your average household microwave oven) Much obliged!
  22. K

    Resonant Frequencies from Fourier Analysis

    I did Fourier analysis on a set of force data from a vibrating string. In my graph of magnitute and frequency, I'm getting major peaks at 62.1 Hz and 249.0 Hz. There is a tiny blip in the data at 125 Hz and nothing at 186 Hz. I have two questions. Do the peaks at 62.1 and 249 mean that those...
  23. H

    What is a simple rule of thumb for determining beat patterns of multiple waves?

    I'm modelling a system that (at the most simple level) is a sum of superimposed waves with different amplitudes. I'll spare all the details but I'd like a nice "rule of thumb" for a beat pattern of multiple waves. The 2-wave beat pattern is obviously nice and easy, but when I was trying to...
  24. M

    Class Limits, Midpoints, Frequencies

    I have a list: 85 45 75 60 90 90 115 30 55 58 78 120 80 65 65 140 65 50 30 125 75 137 80 120 15 45 70 65 50 45 95 70 70 28 40 125 105 75 80 70 90 68 73 75 55 70 95 65 200 75 15 90 46 33 100 65 60 55 85 50 10 68 99 145 45 75 45 95 85 65 65 52 82 Sorry for the poor formatting, but I created a...
  25. V

    Resonant frequencies in a tube with adjustable length

    Problem: Determine the quantity of resonant frequencies that a 1024 Hz tuning fork will have in a 1m long tube with an adjustable water level. Find the length of the air column for each frequency. Assume the speed of sound is 344m/s. Solution: The resonant frequencies are odd integer...
  26. D

    X-ray question - frequencies and energies

    X-ray question -- frequencies and energies Homework Statement 1. Why does x-ray with higher frequency possesses higher ionizing power and penetrating power ? 2. Will gamma ray with higher frequency possesses higher ionizing power and penetrating power ? And is "gamma ray has no mass" a reason...
  27. T

    Why is there no fibre for microwave (or other) frequencies?

    Optical fibre communication depends on total internal reflection at the core-cladding boundary. Why not use the same principle for other portions of the spectrum? After all, total internal reflection occurs at all frequencies.
  28. L

    Question About the Photoelectric Effect for Lower Frequencies

    I'm going over the photoelectric effect and have run into a conceptual problem, and was hoping for some help in resolving it. In particular, I am looking at the frequencies below the threshold frequency of whatever metal is being examined. So, because of the lower frequency, there will be no...
  29. mishima

    Relative Abundance of Light Frequencies?

    I was curious if anyone had ever seen information about how often one frequency of electromagnetic radiation appears in the universe compared to the other. What is the most common frequency or range of frequencies, etc? Is there a way to even estimate this?
  30. C

    Mesh/Nodal analysis with superposition, dependent source and diff frequencies

    Hi, I am preparing for my circuits final and I am having trouble with this question. Can someone guide me through it? I am trying to solve this using phasors. I know I will have to use superposition since the circuit contains sources with different frequencies. So first I start of...
  31. K

    Removing RF Frequencies from Smart Meter w/Capacitor

    I got a dirty electricity problem from a smart meter There is supposedly filters on the market that remove the incoming RF frequencies and puts them onto the neutral. Does anyone know how a capacitor plugged in would remove RF frequencies from the hot wire and send them back on the...
  32. R

    How do I calculate the frequencies of the following?

    7. A steel wire in a piano has a length of 0.9000 m and a mass of 4.000 10-3 kg. To what tension must this wire be stretched so that the fundamental vibration corresponds to middle C (fC = 261.6 Hz on the chromatic musical scale)? 8. The human ear canal is about 2.6 cm long. If it is...
  33. C

    Finding fundamental frequency with length and successive frequencies

    Homework Statement Standing waves on a 1.3 m long string that is fixed at both ends are seen as successive frequencies of 24Hz and 48 Hz. What is the fundamental frequency? Homework Equations fo = nv/4L The Attempt at a Solution Okay, so I don't really know if that is the right...
  34. K

    Natural Frequencies of oscillation

    Homework Statement What are the natural frequencies (not wavelengths) of oscillation formed in a pipe that is open at both ends and a pipe open at one end and closed at the other? Homework Equations The Attempt at a Solution I don't understand this. I keep reading something about 2L and 4L.
  35. R

    Use an Induction Cooktop at different power supply's frequencies?

    Hi everybody, I want to buy a 3kW induction cooktop. The one I intend to buy requires a power source at 220V/60Hz. However, in my country, the main power is 220V/50Hz. Does this difference in frequency cause any incompatible problems? Can I use the induction cooktop in my country? Thanks.
  36. N

    Neuroscience: LFP at fixed point with different simulataneous frequencies

    Hello! I have a neuroscience question about local field potenitals (LFPs). I was reading a jounral article where the LFP in a given location was recorded overtime, and then the LFP at ecah time point was divided into different frequency groups: i.e. the LFP at a given point in space...
  37. T

    Explosive ejection of higher frequencies by lower freq In 2 tesla coils

    Greetings PF'rs I'm researching a phenominon called ball lightning and one supposed method of generating ball lightning is to take two tesla coils of different resonant frequencies but are pulsed with the same secondary coil. The lower frequency coil induces a current in the nearby higher...
  38. I

    Black hole - frequencies used for viewing

    Hey, In space missions why do they choose different frequencies for viewing stars? For example why do they choose both 43 GHz and 230 GHz to view a black hole? Cheers!
  39. O

    High frequencies - dispersive and directional?

    My understanding is that as frequency increases, the wave (or waves, rather) become more directional. However, Plasma Antennas' site specifies operation between 1 and 100GHz, and states their product tightly focussess the beam in order to decrease dispersion. Unless I am totally missing...
  40. D

    How to find cutoff frequencies from Bode plot?

    Homework Statement http://img832.imageshack.us/img832/7517/captureax.jpg According to the solution, the cutoff frequencies are 1, 20, 80, 500 and 8000. I don't understand how to get those answers by inspecting the plot. Homework Equations None The Attempt at a Solution I think the...
  41. K

    Determining Frequencies that Exist in a Signal

    Homework Statement Using trig identities from a calculus book or other, write out the results to the following modulations. State which frequencies exist in the signal s(t). Homework Equations a) s(t) = Acos(2∏f₁t) * Bcos(2∏f₂t)The Attempt at a Solution cos(s) * cos(t) = cos (s + t)/2 + cos (s...
  42. D

    Why are the products of sound wave lengths and frequencies always constant?

    Hi everyone! I was reading a textbook a while ago about waves and it had just finished talking about wave speeds and how it is the product of the frequency times the wave length. On the next page, it gave a table of frequencies and wave lengths of sound waves and how their products are all...
  43. R

    Sound intensity, given frequencies

    Homework Statement The intensity of a sound wave at a fixed dis- tance from a speaker vibrating at 1.31 kHz is 0.894 W/m^2. Determine the intensity if the frequency is increased to 2.33 kHz while a constant dis- placement amplitude is maintained. Answer in units of W/m^2 Homework...
  44. C

    Telegeodynamics and a vivid imagination: If your oscillator changes frequencies

    ...can you manage to get all the surrounding material in the ground to resonate? I'm more of a physics aficionado and not a physicist, so this is more imagination than anything. I was reading up on Tesla's work with Telegeodynamics and his oscillator motor. Essentially, I wanted to know if...
  45. F

    Why AM & FM Broadcasts at Certain Frequencies?

    Hello, looking at the attached graph of noise voltage to frequency, I am trying to understand (from a noise point of view) why AM and FM broadcasts at the frequencies they do ? Can anyone offer any suggestions please ? Thank you.
  46. C

    Why do you get sideband frequencies for amplitude modulation (AM)?

    I thought that the frequency was constant for AM modulation, and just the amplitude was modulated. So why are there a range of frequency's (side bands around the baseband) when the signal is plotted on a frequency domain graph?
  47. W

    Analytical Chemistry UF: Comparing Wavelengths & Frequencies

    Question 20 from our final I just took (Analytical Chemistry UF). "You may recall that the wavelength of the sodium D1 line in vacuum is 589.7558nm. In air it becomes 589.5924nm. What is the difference in frequency for these two wavelengths." I said 0. All the other people did the...
  48. U

    Chi-Squared Test on a table of Binomial Variates - Finding the expected frequencies

    Hi, Carry out a chi-squared test for the following table of frequencies of X ∼ Binomial(5,p) variates when (a) p = 0.3 x 0 1 2 3 4 5 Observed 162 346 303 149 36 4 frequency Now I know how to carry out the chi-squared test once I have...
  49. C

    Question about expected frequencies within ranges

    Say I have ranges: (-infinity to 16) where the observed frequency is 35 (16 to 18) where the obs freq is 100 (18 to 20) where the obs.. freq. is 360 (20 to 22) where the obs. freq. is 326 (22 to 24) where the obs. freq. is 150 (24 to infinity) where the obs freq is 29 The mean is 20 and...
  50. C

    Question about expected frequencies

    Say I have ranges: (-infinity to 16) where the observed frequency is 35 (16 to 18) where the obs freq is 100 (18 to 20) where the obs.. freq. is 360 (20 to 22) where the obs. freq. is 326 (22 to 24) where the obs. freq. is 150 (24 to infinity) where the obs freq is 29 The mean is 20...
Back
Top