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.

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  1. N

    Need help, beat frequencies and tuning.

    Need urgent help, beat frequencies and tuning. Homework Statement http://img144.imageshack.us/img144/4337/2aee8.th.jpg Homework Equations The Attempt at a Solution You can see my attempt in the picture. I assume that beat frequencies are the absolute value of the difference...
  2. P

    Break frequencies for directly coupled transistors

    Homework Statement The problem asks to determine the break frequency at the base of Q2 (which is fine I have no problem with that), but the whole assignment never asks for the break frequency at the COLLECTOR of Q1, then later asks to produce a bode plot of the transfer function. See the image...
  3. S

    Normal frequencies of 2 pendula connected with a massless rigid rod

    Homework Statement I need to figure out the normal frequencies (or eigenfrequencies) of a system of two simple pendula (call them A and B), connected with by a massless rigid rod at an arbitrary distance from the pivot point or the mass. That is, the pendula are not connected at their masses...
  4. baywax

    Radio Frequencies Help Burn Salt Water

    Hello good members and guests of PhysicsForums. Whats the deal with this? Are we going to be fueling vehicles with sea water now? http://green.yahoo.com/index.php?q=node/1570
  5. I

    Transmitting on all frequencies?

    i know you've heard this in a movie or something, usually when a ship is sinking or the last survivor of the human race is looking for other survivors. considering a transmitter is just a driven LRC circuit oscillating at a certain frequency, is this possible? obviously you could have a bunch of...
  6. J

    Understanding the Effects of Wavelength and Frequency on IR and UV Heat Transfer

    hey how come the IR heat up materials more than UV ? and why people say IR go longer distances the way i see it : UV have faster frequencies, they should have more energy while IR have slower frequencies, should have less energy or is it that when hitting a electron , photons that...
  7. O

    Riemann Zeros and Harmonic Frequencies

    Can someone elaborate on the relationship of the Riemann zeros and primes? How are the zeros harmonic to the primes? The quotes below mention the 'sum of its complex zeros' and 'other sums over prime numbers'. Can someone clarify this? From Answers.com: "The zeros of the Riemann...
  8. J

    How Do Light Frequencies Combine to Create New Colors?

    hey i am wondering, what's the equation to find the result equivalent frequence of a mixture of two other different light frequences in same proportions ? (like if u have one red torch , and one blue torch , and u aim the light of each on the same zone) or is the result color not...
  9. R

    How to Calculate Tension for Fundamental Frequency at 60hz

    Fundamental frequencies Using the formula Would it be correct to say that to determine the necessary tension for the fundamental frequency at 60hz, substitute into the equation f, m, and L, then solve for T?
  10. D

    Why Does the System Have a Zero Frequency in the Normal Mode Oscillations?

    Homework Statement Two equal masses are connected by two massless springs of constant k and nat. length l. The masses are constrained by a frictionless tube on a pivot, (also massless) so that they remain colinear with the pivot. The pivot subtends angle theta with the vertical. The 1st mass...
  11. P

    Standing Wave Frequencies in Wire & Pipe: Similarities & Differences

    -Look up or derive the frequencies of the standing waves of a length of wire, L, clamped at the ends and under tension. -What are the similarities and differences between a vibrating string and a resonating pipe? -Does the diameter of the wire matter? -Does the diameter of the pipe matter...
  12. C

    Are EM radiation frequencies quantified?

    Maybe the wrong word but can you get electromagnetic radiation in any frequency or is there a "quantum" frequency for which all other frequencies are some integer multiple? Related question - is there an absolute low and high frequency?
  13. J

    Mathematica 'Mathematical' frequencies and photons

    It is known that any non-sinusoidal wave can be regarded as a combination of sinusoidal waves of different frecuencies, with the ‘weight’ of the different frecuencies given by the function called Fourier transform. On the other hand, if we have an electromagnetic wave, we know that it is the...
  14. S

    Fundamental Frequencies of Noble Metals

    Hello, I need to know the fundamental frequencies of the noble metals "silver, gold, platinum ... etc" .. thank you very much
  15. F

    Fundamental frequencies and temperature

    Homework Statement The frequency of the note f_4 is f_F. If an organ pipe is open at one end and closed at the other, what length must it have for its fundamental mode to produce this note at a temperature of T? ans= v/(4*f_F), where v is the speed of sound in air. Now the part which...
  16. K

    Combining high frequencies to get a large frequency

    "Combining high frequencies to get a large frequency" "Combining high frequencies to get a large wavelength" Is this possible? There will be constructive and destructive interference, but can there be anything that increases the wavelength?
  17. J

    Mixing Frequencies: Summing vs Multiplication - Jason O

    Hello All, I have two questions regarding mixing of frequencies. I heard that there is a difference between two waves that simply ‘add’ mathematically, and two waves that are ‘multiplied’ mathematically. If I have two frequencies, say 10Hz and 11Hz and I add the waves together so that they...
  18. A

    Calculating Frequencies from SparkGap Voltage/Current Data

    If you konw the voltage and current as a function of time of a spark acorss a sparkgap, can you calculate the frequencies? If so, how?
  19. D

    Modulation in high frequencies and antennas

    Hi to everyone. I have heard that we usually prefer to modulate signals at high frequencies so the wave length is small compared to the length of the antenna. Is there any rule or equation that implies this requirement?
  20. Ivan Seeking

    Metamaterial Electromagnetic Cloak at Microwave Frequencies

    If you happen to see microwaves... Scientists Take Step Toward Invisibility http://www.nytimes.com/2006/10/20/science/20cloak.html?hp&ex=1161316800&en=cd2cdec26f18ae3a&ei=5094&partner=homepage See also: http://www.ee.duke.edu/~drsmith/cloaking.html
  21. K

    Just wondering about frequencies

    Hey guys, long time no see. I was flipping through a book about black holes and gravity when i saw a chart about different frequencies and I came up with a little thought that would be nice to have explained. Why is it that lower frequencies (radio/microwave) and higher (x-ray/gamma ray) can...
  22. A

    Quantum Physics & Electromagnetic Frequencies

    What is the relationship between Quantum Physics and electromagnetic frequencies?
  23. D

    Atomic transition and cavity axial-mode frequencies

    Hello folks, I would like to know whether or not the cavity axial-mode frequencies have any influence on the frequency output of the laser beam. I suppose that the atomic transition from excited state to ground state is the only occurrence responsible for the wavelength, whereas the axial-mode...
  24. S

    Visualizing audible frequencies

    Is it possible? It is said that the human being can hear from a dynamic range of 20 hz to 20,000 hz. Apparently, the human eye is not able to detect audible frequencies. I have a question though... Can we see audible frequencies? Our are eyes capable of catching them? If a drop of...
  25. R

    What is the exact formula for calculating bubble resonance frequencies?

    This is very important. Can someone tell the dependency for the resonance frequencies of bubbles? i.e if know a bubble's diameter, the surface tension, the liquid and the gas' densities how do I calculate the sound wave frequencies that causes a resonance in a bubble. I have Landau's formula...
  26. L

    Fundamental Frequencies and Standing Waves

    Evening, Ive been having some trouble with questions about fundamental frequencies and labelling nodes and anti nodes in an air column. for example :a tuning fork is placed above a glass tube and then the sound of the air column is adjusted by raising or lowering the glass tube in the...
  27. D

    Redshifts, what frequencies are they looking at?

    I looked at a spectrogram of our sun several months ago. It contained a whole plethora of frequencies. It appeared that there were many thousands of frequencies in the visible spectrum alone. When scientists investigate redshifts, do they look at a specific frequency, or do they just...
  28. J

    Beat Frequency: Can Inductive Coupling Work?

    Hi, here’s my question. If I make an oscillator that resonates at 6kHz and a second oscillator that resonates at 5kHz, the magnetic field produced by the coils of the two oscillators would be 1000Hz (please correct me here if I have made an incorrect assumption). If I have a 1000Hz signal that I...
  29. T

    How to Achieve High Pulsing Frequencies with Lasers

    Hi, just out of curiosity, i heard about a new electron gun (if that's the proper term) using a laser pulsing at about 3.333 x 10e14 Hz to increase the frequency at which the electrons are emitted. How does the laser reach such pulsing frequencies? Thanks.
  30. C

    Highest attainable frequencies by a transmitter

    what is the highest attainable frequencie by an oscillator circuit? :confused:
  31. R

    Lower Frequencies pass through materials easier?

    This is a question that has been bugging me for quite and long time and I have been searching on the Internet, but having no luck. So, why does lower frequency sound pass through materials much easier then higher? Thanks, Rich
  32. L

    Medical Certain sound frequencies to induce mind moods

    When i was a kid i read the first book on hitscock the 3 investigators Bob Pete and Jupiter the castle of terror where everytime they would go to the castle they would be terrify, in the end an old movie star would have been hiding in the castle and scare people by using a certain no audible...
  33. D

    Natural and Fundamental Frequencies

    How could you tell if you had missed one of the natural frequencies when you were finding natural frequencies above the fundamental? thnx a lot
  34. P

    Galactic Frequencies: Info on Frequency of Galaxies

    I was wondering if there is any info on the frequencies of individual galaxies?
  35. C

    Calculate the expected frequencies of 3,4,5 and 6 eggs

    Hello, i found one question really difficult and I can't solve it. Please help. Six hens are observed over a period of 20 days and the number of eggs laid each day is summarised in the following table: No. of eggs: 3 4 5 6 No. of days: 2 2 10 6 This can be considered as a...
  36. M

    Dealing with wavelengths, frequencies and speed

    Ok, I am working with problems dealing with Speed=(lambda) (frequency). I have a question in determining whether I am solving these correctly. I sometimes get confused as what the wavelength is. 1. A longitudinal wave with a frequency of 25.0Hz travels along a coil spring. If the distance...
  37. K

    Understanding Resonance & Tuning Forks

    Hi. I'm having some trouble understanding resonance. I was reading about how ears work on howstuffworks.com, and it noted that the ear picks up different frequencies basically because little hairs inside the ear resonate at different freqencies. It said that this is also the concept behind...
  38. H

    High Frequencies in Computer CPUs

    Hi Everyone, I just joined the forum and would like to extend a big hello to everyone! I had a look around the forum and it's a treasure trove of information. Congrats to everyone... I have a question that my father keeps asking and I don't know the answer to this one: Why don't the...
  39. M

    Deteriming resonant frequencies

    I am stumped on how exactly to do this. I have the function: T(s) = 7/s(s^2+6s+58) I need to change this to T(iω) and i being a complex root. This creates: T(iω) = 7/(ωi*(ω^2+6iω+58)) I know I need to plot this function and find out where omega peaks and this will be my resonant...
  40. A

    Generating mechanical frequencies

    Hi there ! I have a question : does a mechanical system generating a lower frequency when excited with a hig frequency exists ? In this case, would it be possible to start stimulated processes of emission of a lower frequency from a high frequency ? Then, we could imagine a kind of laser not...
  41. P

    Does the Speed of Light Change depending on different Light Frequencies?

    We all know that light speed in a vacuum is constant and travels 9.8 X 1018 meters in a year. Now since light travels in waves instead of a straight line, if the wave was then uncurved, it would cover more distance than when it was in its original state. Of course different lights have...
  42. E

    Exploring the Possibility of Sound Beyond 20kHz: Vibrations & Frequencies

    I'm currently studying vibrations and frequencies. I know that humans can hear from a range of 20Hz-20kHz. I was wondering if sound energy could reach a frequency where it was no longer really sound. Is this possible?
  43. L

    Max and min frequencies of a capacitor

    A variable capacitor with a range from 10 to 365 p is used with a coil to form a variable frequency LC circuit t0 tune the input to a radio. a. What ratio of max and min frequencies may be obtained with such capcitor. I used that \omega=\frac 1{\sqrt(LC)} to get the ratio of max to min...
  44. S

    Understanding Color Vision: Mixtures & Frequencies

    I'm not sure if this is the right forum for it, but I had a few questions about how color vision works. I know that mixtures of pure colors look like other pure colors. For example, some mixture of pure (monochromatic) green and blue looks like pure yellow. So for a given color, are there an...
  45. B

    How can atomic spectra be only certin frequencies?

    I don't know a whole lot about quantum mechanics and there is something that dosen't make sense to me. An atom absorbes radiation in only certin frequencies. Do these frequencies have to be exact? Can they vary over a small range like say 1.000 to 1.001 or do they have to be perfectly exact...
  46. S

    String Frequencies: Does It Make Sense?

    Does it make any sense to ask at what frequencies stings vibrate? If so, is there a source that provides information along these lines?
  47. L

    2 frequencies within an interference pattern

    Hi, short question. What would be the effect of 2 sources both transmitting 2 different frequencies if placed in a way that forms an interference pattern. ie. 2 aerials places parallel X meters apart transmitting in the same direction at 2 different frequencies per aerial. Sorry if i...
  48. O

    Brain Signals & Frequencies: Is Beta Wave Real?

    does the brain send out signals or frequencies. I believe i recall hearing about something like beta waves perhaps it was. Someone know of this?
  49. Y

    What are the lowest two frequencies of the sound?

    I am having a problem finding where to start. The problem is this: A loudspeaker at the orgin emits sound waves on a day where the speed of sound is 340 m/s. A crest of the wave simultaneously passes listeners at the (x,y) coordinates (40m,0m) and (0m,30m). What are the lowest two frequencies of...
  50. V

    Transformer efficiency at low (and high) frequencies

    Hello, I've been thinking about why (elementary) transformer efficiency drops drastically at very low frequencies. I know hysteresis effects play a major role in reducing efficiency at high frequencies, but why low? I realize that as we reduce the frequency of the emf, we're making the...
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