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Text has been copied to or from this article; see the list below. The source pages now serve to provide attribution for the content in the destination pages and must not be deleted as long as the copies exist. For attribution and to access older versions of the copied text, please see the history links below. |
Is it not true that the A tuning note is only 440 Hz in the United States, while in fact 442 Hz in Europe? Perhaps this should be changed. — Preceding unsigned comment added by Trhaynes ( talk • contribs) 18:27, 3 December 2004 (UTC)
I was just wondering about the comment that when a wave goes from one medium to another, the frequency remains more or less the same, only the wavelength changes -- this doesn't make sense to me. If frequency has an inverse relationship to wavelength, how can one change without the other? — Preceding unsigned comment added by 131.172.4.45 ( talk) 03:50, 13 April 2005 (UTC)
Just wondering if any one has thought about why frequency is invariant (apart from doppler effect). ie whatever you do to a signal, you can change its wavelength and or velocity but you cant change its frequency. (I'm not considering mixers here). Any musings from anyone as to why this should be so?? -- Light current 06:52, 23 November 2005 (UTC)
Quite correct about pre recorded signals, but Im thinking more of a 'pitch shifting' method but broad band and not using mixers (multipliers). I guess it just can't be done? -- Light current 22:07, 12 December 2005 (UTC)
I removed from the bottom of the section Frequency of waves:
Apart from being modified by the Doppler effect or any other nonlinear process, frequency is an invariant quantity in the universe. That is, it cannot be changed by any linearly physical process unlike velocity of propagation or wavelength.
My motivation is:
Kraaiennest ( talk) 17:07, 22 February 2008 (UTC)
We have a rather strange paragraph that tells us how to measure frequency by dividing one number by another which is of course true. But do we have anything about various classes of frequency meter - i.e. how we actually measure frequency? Pcb21 Pete — Preceding undated comment added 10:54, 17 April 2006 (UTC)
In my opinion, this is not a unit of frequency, but of angular frequency. -- 84.159.248.246 17:04, 20 November 2006 (UTC)
I removed the non sequitur "Notes" heading and its entry about the human heartbeat being close to one Hertz. Actually, the human heartbeat varies quite a bit--it can get down to 0.8 Hertz in mellow marathoners and up to 2 Hz in times of high stress activity. Average heart rate is about 72 bpm, or 1.2 Hz. No studies support the statement that the heartbeat is exactly 60 beats per minute which means there's no benefit to the reader by announcing that the heartbeat is approximately 1 Hz. It doesn't shed any light on the concept of frequency. Binksternet ( talk) 08:36, 25 January 2008 (UTC)
Mean zero up-crossing period, TZ or Tm0,2
When recordings were first taken this was onto charts and simple counts could be made. First the charts were zero-meaned (the average and trend calculated and drawn through the plot to provide a new axis for measuring) and then the number of times the wave record crossed the mean going up (or sometimes down) was counted and this gave the number of waves and, as a time measure, the zero-crossing period. The parameter is estimated by taking the mean of these periods for a given wave record. For wave records on paper the mean level is found by eye and Tvisual is estimated from the record length and the number of zero up-crossings counted on the record. This method can also be applied to digitised data using a computer but if the wave records are available in machine readable form it is preferable to estimate from the moments of the spectrum using,
Tz=
where the mi values are spectral moments. The alternative symbol of Tm0,2 is derived from the moment equation. It can be seen that TZ is very dependent on the higher frequency end of the spectrum and although TZ is the most commonly used period estimator it is not very stable.
Significant wave period, Ts
The significant wave period is the mean of the zero up-crossing periods associated with the highest one third of the waves. It is sometimes denoted by Ts. Note that this parameter cannot be obtained directly from the wave spectrum. It is not very useful, but sometimes is used!
Spectral peak period, Tp
The spectral peak period is the inverse of the frequency at which the value of the frequency spectrum is a maximum. It cannot be defined satisfactorily in multi-peaked spectra. fp is very important in characterising spectra.
Period associated with the most likely highest wave, Tmax
The most likely height of the highest wave in a record of duration 3 hours is Hmax and Tmax is its period. It is often obtained indirectly from Tz or Tp using empirical relationships, or from Hmax and steepness assumptions – usually to obtain a range of possible associated periods. These methods should be applied only in the water depth for which the empirical relationships have been found, usually deep water (i.e. depth >1/2 wavelength). It should be possible to use the steepness method in shallow water provided that refraction is minimal and that allowance can be made for shoaling effects. It cannot, however, be derived directly from the wave spectrum.
Energy period, Te
This period is important for power estimation and is used in wave power design as a preferred comparator. The most appropriate way to consider energy period is as the period of the regular wave that has the same significant height and the same power density as the sea-state under consideration. It is defined as,
Te=
Because of the relationship with power it is worth giving the expression for time averaged power associated with a spectrum,
power = rho g^2 m0 Te / 4Pi
Hence we can find an expression for Te as follows,
Te=(64 Pi Power)/ rho g^2 Hs^2
Average wave period, Tav
This is the inverse of the average frequency calculated from the mean of all component sine waves weighted by the spectral energy. It cannot be measured in the time domain unless the waves are simple sine curves.
Average crest period, Tc
Defined as, Tc=
This is equivalent to dividing the length of the wave record by the number of crests where a crest is any point either side of which the surface elevation decreases. Crests are not necessarily associated with zero up-crossings. Clearly this is very much influenced by the ‘tail’ of the spectrum through the fourth moment.
(copied from Talk:Wave period by Kraaiennest ( talk) 21:46, 10 February 2008 (UTC)).
I have removed the following from the "Definitions and units" section:
(1) The text, if it belongs in the article at all, is in the wrong section. The text does not belong here. There is a long list of things for which the concept of frequency is important, we aren't going to talk about all of them in the "definitions and units" section. (2) The text is true but not true enough: (2a) With waves speed is always "mathematically related" (i.e. equal to the product) to frequency and wavelength, that fact is not specific to "wireless communications". (2b) The 300 used is the speed of light in a vacuum, although we neglect to mention that point, but this isn't the page for quick rule-of-thumb formulae for radio technicians. (2c) Elementary maths gives us one formula from the other so, once again, not useful here. (3) Everything is already covered in the "physics of light" example section.
Paul Beardsell ( talk) 19:22, 15 March 2009 (UTC)
I think most of the 'Physics of sound' section should be removed. Description of longitudinal vs. transverse waves, polarization, etc. are not necessary for the explanation of frequency of sound waves, and simply repeat coverage in other articles. This is where 'Wikipedia bloat' comes from. All that should appear is a simple exposition of sound wave frequency, mention of how it's measured, and maybe something on the 'spectrum' of sound frequencies analogous to the spectrum of electromagnetic waves. -- Chetvorno TALK 22:58, 17 March 2009 (UTC)
The last citation link links to xkcd for absolutely no reason. —Preceding unsigned comment added by 71.228.164.178 ( talk) 02:25, 9 June 2009 (UTC)
XKCD are currently running a campaign to vandalise the wikipedia of every subject the comic touches upon. —Preceding unsigned comment added by 217.23.232.41 ( talk) 15:47, 10 June 2009 (UTC)
Frequency in Fourier analysis is a different concept from 1/(period). I don't have time to write an explanation now but I think that concept, and links to appropriate articles, would be helpful here. Ccrrccrr ( talk) 23:25, 19 February 2010 (UTC)
Please add some data to the article saying what variables of waves in sound and light depend on the frequency of the wave. eg speed, impedance, refracting index, attenuation coefficient, etc. —Preceding unsigned comment added by 91.99.166.67 ( talk) 10:50, 10 May 2010 (UTC)
Prior content in this article duplicated one or more previously published sources. The material was copied from: http://www.wavesignal.com/Light/index.html (content was added in February 2009; archives confirm their prior publication. Infringing material has been rewritten or removed and must not be restored, unless it is duly released under a compatible license. (For more information, please see "using copyrighted works from others" if you are not the copyright holder of this material, or "donating copyrighted materials" if you are.) For legal reasons, we cannot accept copyrighted text or images borrowed from other web sites or published material; such additions will be deleted. Contributors may use copyrighted publications as a source of information, but not as a source of sentences or phrases. Accordingly, the material may be rewritten, but only if it does not infringe on the copyright of the original or plagiarize from that source. Please see our guideline on non-free text for how to properly implement limited quotations of copyrighted text. Wikipedia takes copyright violations very seriously, and persistent violators will be blocked from editing. While we appreciate contributions, we must require all contributors to understand and comply with these policies. Thank you. Moonriddengirl (talk) 21:43, 22 December 2010 (UTC)
There ought to be an overview of how frequency is relevant to your perception of, say, light and sound in the lead. I can't tell you how many audio-related pages link to this one, expecting it to explain how frequency is the property of sound that most determines pitch. Until just now it didn't. I've added a very brief explanation of frequency's relationship to pitch in the Physics of sound section.
But, I think this ought to be stated in the lead as well so that readers will know why they'd been linked to the frequency page right away.-- Atlantictire ( talk) 20:59, 26 April 2011 (UTC)
Dicklyon, I doubt you're conflicted in a bad way and I hope you reconsider.
The quote is:
The main problem that I see is that if the sound wave is, say, five seconds of human speech, it doesn't really have a pitch and it doesn't really have a frequency. Another problem is that people who don't know how sound work will wonder what it means for sound to have a frequency. So then I thought, how about
This sort of answers my first complaint above but not the second. Anyway, this isn't very good because "oscillating sound wave" probably makes people think of like tremolo or vibrato, which is totally different. Another problem is that, even if the waveform is exactly oscillatory, the oscillation frequency is not necessarily related to the pitch...for example when you play two pure tones together, the waveform oscillates at the beat frequency, but you can't hear the beat frequency at all if it's in the audible range. So then I thought
OK, now this is accurate I think...but maybe too many words and too many new concepts for readers ("what does sinusoidally mean?, etc...") Or maybe it's OK? Or maybe a better approach is to take P1 and just slap a giant footnote on it... I'll think more later. :-P -- Steve ( talk) 01:54, 4 May 2011 (UTC)
Somewhere between 1,000 and 4,500 people visit this page every day. I think it might be useful to take a look at the pages that link here to try and get a sense of what the readers' needs are, and then to expand the lead so as to better orient them. It's nice after you've clicked on a link to a page to know from the lead why you're there. As someone who's just started learning about audio engineering concepts, I have to say I couldn't tell right away what frequency had to do with anything... and then I figured it out and added information about pitch. Yes, some of us really are that dumb!:)-- Atlantictire ( talk) 02:58, 1 May 2011 (UTC)
So what is the criterion for using f instead of the Greek letter ν? As far as I know ν is a more widely used symbol for frequency. — Preceding unsigned comment added by 188.83.90.251 ( talk) 16:10, 12 June 2011 (UTC)
I reworked these old sections by departed User:Logger9, and renamed them to be just Light and Sound, since they're supposed to be about frequency, not about physics. It's interesting that the sound one says "Frequency is the property of sound that most determines pitch," which is true for repetitive sound waves according to the definition of frequency given, but completely misses the opportunity to address the oft-discussed disconnect between frequency and pitch in psychoacoustics. Project for another time... Dicklyon ( talk) 17:58, 18 January 2014 (UTC)
Rename to Temporal frequency and keep Frequency as a redirect here. Not asking to change the scope of this article, just to have its title reflecting the scope more accurately. Thanks. Fgnievinski ( talk) 16:16, 21 October 2014 (UTC)
As per wikt:frequency, the first definition of frequency is "The rate of occurrence of anything; the relationship between incidence and time period [or interval]" -- there's nothing about periodic/oscillating/cyclic in it, it's just the ratio of incidence count over time duration. Fgnievinski ( talk) 06:57, 19 July 2015 (UTC)
I don't see the need for doing this. The article is not particularly large, nowhere near splitting size, and the Measurement section itself is not large. -- Chetvorno TALK 04:59, 23 July 2015 (UTC)
I propose to replace the subsection Frequency#Examples#Light with the following. I think the present section invites readers unfamiliar with quantum mechanics into waters too deep. (I am unsure about that page 111 in the 2nd edition. I am also unsure whether I should have left this code in a sandbox, but I feared a sandbox may be too volatile for the archive.)
Radio waves and microwaves are electromagnetic waves, consisting of spatially orthogonal electric and magnetic fields oscillating together in both time and space, traveling through space. The wavelengths are in the range of many meters to a few millimeters, corresponding to frequencies that can be directly measured in the time domain by observing the electrical signals induced in an antenna detecting the waves.
Visible light is also electromagnetic radiation with much shorter wavelength, in the 400 to 700 nm range. In scientific observations, it is detected as a stream of massless elementary particles called photons, each with an energy conventionally in the range 2.9 to 4.6 electronvolts. (At low light intensities, these particles can be individually counted by a sufficiently sensitive photodetector.) In common with other subatomic particles, even massive examples such as cold neutrons, streams of multiple photons arrive at detectors in spatial distributions that reflect wave-like propagation, displaying interference and diffraction. Hence a wavelength associated with any particle of such type can be directly measured using an interferometer. This applies also to massive particles such as neutrons.
From the measured wavelength and speed of photons, what is conventionally called a "frequency" can be calculated in the usual way:
where c is the speed of light ( c in a vacuum, or less in other media), f is the frequency and λ is the wavelength.
Regarding the interpretation of these quantities, Feynman provided the following advice: [1]
We cannot say whether light is particle or wave. This is not an either/or situation; light seems to be both particles and waves and thus is probably neither.
Visible light shares that duality with, e.g., cold neutrons, the "frequency" of which is rarely mentioned.
Layzeeboi ( talk) 07:36, 12 February 2017 (UTC)
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@ Boppennoppy: Hi, see it implicitly means 1 event, and 1 here is full of meaning, but (number of) event has no dimension, because it is a number. So Hertz not means "one per second", but it means "one event per second", i.e., one (or 1) here, is full of meaning. Hertz does not mean 1 "kilometer" per second or one "kilogram" per second or anything else, it means one "event" per second. Hooman Mallahzadeh ( talk) 16:14, 30 December 2021 (UTC)
This
level-4 vital article is rated C-class on Wikipedia's
content assessment scale. It is of interest to the following WikiProjects: | ||||||||||||||||||||||||||||||||||||||||||||
|
Text has been copied to or from this article; see the list below. The source pages now serve to provide attribution for the content in the destination pages and must not be deleted as long as the copies exist. For attribution and to access older versions of the copied text, please see the history links below. |
Is it not true that the A tuning note is only 440 Hz in the United States, while in fact 442 Hz in Europe? Perhaps this should be changed. — Preceding unsigned comment added by Trhaynes ( talk • contribs) 18:27, 3 December 2004 (UTC)
I was just wondering about the comment that when a wave goes from one medium to another, the frequency remains more or less the same, only the wavelength changes -- this doesn't make sense to me. If frequency has an inverse relationship to wavelength, how can one change without the other? — Preceding unsigned comment added by 131.172.4.45 ( talk) 03:50, 13 April 2005 (UTC)
Just wondering if any one has thought about why frequency is invariant (apart from doppler effect). ie whatever you do to a signal, you can change its wavelength and or velocity but you cant change its frequency. (I'm not considering mixers here). Any musings from anyone as to why this should be so?? -- Light current 06:52, 23 November 2005 (UTC)
Quite correct about pre recorded signals, but Im thinking more of a 'pitch shifting' method but broad band and not using mixers (multipliers). I guess it just can't be done? -- Light current 22:07, 12 December 2005 (UTC)
I removed from the bottom of the section Frequency of waves:
Apart from being modified by the Doppler effect or any other nonlinear process, frequency is an invariant quantity in the universe. That is, it cannot be changed by any linearly physical process unlike velocity of propagation or wavelength.
My motivation is:
Kraaiennest ( talk) 17:07, 22 February 2008 (UTC)
We have a rather strange paragraph that tells us how to measure frequency by dividing one number by another which is of course true. But do we have anything about various classes of frequency meter - i.e. how we actually measure frequency? Pcb21 Pete — Preceding undated comment added 10:54, 17 April 2006 (UTC)
In my opinion, this is not a unit of frequency, but of angular frequency. -- 84.159.248.246 17:04, 20 November 2006 (UTC)
I removed the non sequitur "Notes" heading and its entry about the human heartbeat being close to one Hertz. Actually, the human heartbeat varies quite a bit--it can get down to 0.8 Hertz in mellow marathoners and up to 2 Hz in times of high stress activity. Average heart rate is about 72 bpm, or 1.2 Hz. No studies support the statement that the heartbeat is exactly 60 beats per minute which means there's no benefit to the reader by announcing that the heartbeat is approximately 1 Hz. It doesn't shed any light on the concept of frequency. Binksternet ( talk) 08:36, 25 January 2008 (UTC)
Mean zero up-crossing period, TZ or Tm0,2
When recordings were first taken this was onto charts and simple counts could be made. First the charts were zero-meaned (the average and trend calculated and drawn through the plot to provide a new axis for measuring) and then the number of times the wave record crossed the mean going up (or sometimes down) was counted and this gave the number of waves and, as a time measure, the zero-crossing period. The parameter is estimated by taking the mean of these periods for a given wave record. For wave records on paper the mean level is found by eye and Tvisual is estimated from the record length and the number of zero up-crossings counted on the record. This method can also be applied to digitised data using a computer but if the wave records are available in machine readable form it is preferable to estimate from the moments of the spectrum using,
Tz=
where the mi values are spectral moments. The alternative symbol of Tm0,2 is derived from the moment equation. It can be seen that TZ is very dependent on the higher frequency end of the spectrum and although TZ is the most commonly used period estimator it is not very stable.
Significant wave period, Ts
The significant wave period is the mean of the zero up-crossing periods associated with the highest one third of the waves. It is sometimes denoted by Ts. Note that this parameter cannot be obtained directly from the wave spectrum. It is not very useful, but sometimes is used!
Spectral peak period, Tp
The spectral peak period is the inverse of the frequency at which the value of the frequency spectrum is a maximum. It cannot be defined satisfactorily in multi-peaked spectra. fp is very important in characterising spectra.
Period associated with the most likely highest wave, Tmax
The most likely height of the highest wave in a record of duration 3 hours is Hmax and Tmax is its period. It is often obtained indirectly from Tz or Tp using empirical relationships, or from Hmax and steepness assumptions – usually to obtain a range of possible associated periods. These methods should be applied only in the water depth for which the empirical relationships have been found, usually deep water (i.e. depth >1/2 wavelength). It should be possible to use the steepness method in shallow water provided that refraction is minimal and that allowance can be made for shoaling effects. It cannot, however, be derived directly from the wave spectrum.
Energy period, Te
This period is important for power estimation and is used in wave power design as a preferred comparator. The most appropriate way to consider energy period is as the period of the regular wave that has the same significant height and the same power density as the sea-state under consideration. It is defined as,
Te=
Because of the relationship with power it is worth giving the expression for time averaged power associated with a spectrum,
power = rho g^2 m0 Te / 4Pi
Hence we can find an expression for Te as follows,
Te=(64 Pi Power)/ rho g^2 Hs^2
Average wave period, Tav
This is the inverse of the average frequency calculated from the mean of all component sine waves weighted by the spectral energy. It cannot be measured in the time domain unless the waves are simple sine curves.
Average crest period, Tc
Defined as, Tc=
This is equivalent to dividing the length of the wave record by the number of crests where a crest is any point either side of which the surface elevation decreases. Crests are not necessarily associated with zero up-crossings. Clearly this is very much influenced by the ‘tail’ of the spectrum through the fourth moment.
(copied from Talk:Wave period by Kraaiennest ( talk) 21:46, 10 February 2008 (UTC)).
I have removed the following from the "Definitions and units" section:
(1) The text, if it belongs in the article at all, is in the wrong section. The text does not belong here. There is a long list of things for which the concept of frequency is important, we aren't going to talk about all of them in the "definitions and units" section. (2) The text is true but not true enough: (2a) With waves speed is always "mathematically related" (i.e. equal to the product) to frequency and wavelength, that fact is not specific to "wireless communications". (2b) The 300 used is the speed of light in a vacuum, although we neglect to mention that point, but this isn't the page for quick rule-of-thumb formulae for radio technicians. (2c) Elementary maths gives us one formula from the other so, once again, not useful here. (3) Everything is already covered in the "physics of light" example section.
Paul Beardsell ( talk) 19:22, 15 March 2009 (UTC)
I think most of the 'Physics of sound' section should be removed. Description of longitudinal vs. transverse waves, polarization, etc. are not necessary for the explanation of frequency of sound waves, and simply repeat coverage in other articles. This is where 'Wikipedia bloat' comes from. All that should appear is a simple exposition of sound wave frequency, mention of how it's measured, and maybe something on the 'spectrum' of sound frequencies analogous to the spectrum of electromagnetic waves. -- Chetvorno TALK 22:58, 17 March 2009 (UTC)
The last citation link links to xkcd for absolutely no reason. —Preceding unsigned comment added by 71.228.164.178 ( talk) 02:25, 9 June 2009 (UTC)
XKCD are currently running a campaign to vandalise the wikipedia of every subject the comic touches upon. —Preceding unsigned comment added by 217.23.232.41 ( talk) 15:47, 10 June 2009 (UTC)
Frequency in Fourier analysis is a different concept from 1/(period). I don't have time to write an explanation now but I think that concept, and links to appropriate articles, would be helpful here. Ccrrccrr ( talk) 23:25, 19 February 2010 (UTC)
Please add some data to the article saying what variables of waves in sound and light depend on the frequency of the wave. eg speed, impedance, refracting index, attenuation coefficient, etc. —Preceding unsigned comment added by 91.99.166.67 ( talk) 10:50, 10 May 2010 (UTC)
Prior content in this article duplicated one or more previously published sources. The material was copied from: http://www.wavesignal.com/Light/index.html (content was added in February 2009; archives confirm their prior publication. Infringing material has been rewritten or removed and must not be restored, unless it is duly released under a compatible license. (For more information, please see "using copyrighted works from others" if you are not the copyright holder of this material, or "donating copyrighted materials" if you are.) For legal reasons, we cannot accept copyrighted text or images borrowed from other web sites or published material; such additions will be deleted. Contributors may use copyrighted publications as a source of information, but not as a source of sentences or phrases. Accordingly, the material may be rewritten, but only if it does not infringe on the copyright of the original or plagiarize from that source. Please see our guideline on non-free text for how to properly implement limited quotations of copyrighted text. Wikipedia takes copyright violations very seriously, and persistent violators will be blocked from editing. While we appreciate contributions, we must require all contributors to understand and comply with these policies. Thank you. Moonriddengirl (talk) 21:43, 22 December 2010 (UTC)
There ought to be an overview of how frequency is relevant to your perception of, say, light and sound in the lead. I can't tell you how many audio-related pages link to this one, expecting it to explain how frequency is the property of sound that most determines pitch. Until just now it didn't. I've added a very brief explanation of frequency's relationship to pitch in the Physics of sound section.
But, I think this ought to be stated in the lead as well so that readers will know why they'd been linked to the frequency page right away.-- Atlantictire ( talk) 20:59, 26 April 2011 (UTC)
Dicklyon, I doubt you're conflicted in a bad way and I hope you reconsider.
The quote is:
The main problem that I see is that if the sound wave is, say, five seconds of human speech, it doesn't really have a pitch and it doesn't really have a frequency. Another problem is that people who don't know how sound work will wonder what it means for sound to have a frequency. So then I thought, how about
This sort of answers my first complaint above but not the second. Anyway, this isn't very good because "oscillating sound wave" probably makes people think of like tremolo or vibrato, which is totally different. Another problem is that, even if the waveform is exactly oscillatory, the oscillation frequency is not necessarily related to the pitch...for example when you play two pure tones together, the waveform oscillates at the beat frequency, but you can't hear the beat frequency at all if it's in the audible range. So then I thought
OK, now this is accurate I think...but maybe too many words and too many new concepts for readers ("what does sinusoidally mean?, etc...") Or maybe it's OK? Or maybe a better approach is to take P1 and just slap a giant footnote on it... I'll think more later. :-P -- Steve ( talk) 01:54, 4 May 2011 (UTC)
Somewhere between 1,000 and 4,500 people visit this page every day. I think it might be useful to take a look at the pages that link here to try and get a sense of what the readers' needs are, and then to expand the lead so as to better orient them. It's nice after you've clicked on a link to a page to know from the lead why you're there. As someone who's just started learning about audio engineering concepts, I have to say I couldn't tell right away what frequency had to do with anything... and then I figured it out and added information about pitch. Yes, some of us really are that dumb!:)-- Atlantictire ( talk) 02:58, 1 May 2011 (UTC)
So what is the criterion for using f instead of the Greek letter ν? As far as I know ν is a more widely used symbol for frequency. — Preceding unsigned comment added by 188.83.90.251 ( talk) 16:10, 12 June 2011 (UTC)
I reworked these old sections by departed User:Logger9, and renamed them to be just Light and Sound, since they're supposed to be about frequency, not about physics. It's interesting that the sound one says "Frequency is the property of sound that most determines pitch," which is true for repetitive sound waves according to the definition of frequency given, but completely misses the opportunity to address the oft-discussed disconnect between frequency and pitch in psychoacoustics. Project for another time... Dicklyon ( talk) 17:58, 18 January 2014 (UTC)
Rename to Temporal frequency and keep Frequency as a redirect here. Not asking to change the scope of this article, just to have its title reflecting the scope more accurately. Thanks. Fgnievinski ( talk) 16:16, 21 October 2014 (UTC)
As per wikt:frequency, the first definition of frequency is "The rate of occurrence of anything; the relationship between incidence and time period [or interval]" -- there's nothing about periodic/oscillating/cyclic in it, it's just the ratio of incidence count over time duration. Fgnievinski ( talk) 06:57, 19 July 2015 (UTC)
I don't see the need for doing this. The article is not particularly large, nowhere near splitting size, and the Measurement section itself is not large. -- Chetvorno TALK 04:59, 23 July 2015 (UTC)
I propose to replace the subsection Frequency#Examples#Light with the following. I think the present section invites readers unfamiliar with quantum mechanics into waters too deep. (I am unsure about that page 111 in the 2nd edition. I am also unsure whether I should have left this code in a sandbox, but I feared a sandbox may be too volatile for the archive.)
Radio waves and microwaves are electromagnetic waves, consisting of spatially orthogonal electric and magnetic fields oscillating together in both time and space, traveling through space. The wavelengths are in the range of many meters to a few millimeters, corresponding to frequencies that can be directly measured in the time domain by observing the electrical signals induced in an antenna detecting the waves.
Visible light is also electromagnetic radiation with much shorter wavelength, in the 400 to 700 nm range. In scientific observations, it is detected as a stream of massless elementary particles called photons, each with an energy conventionally in the range 2.9 to 4.6 electronvolts. (At low light intensities, these particles can be individually counted by a sufficiently sensitive photodetector.) In common with other subatomic particles, even massive examples such as cold neutrons, streams of multiple photons arrive at detectors in spatial distributions that reflect wave-like propagation, displaying interference and diffraction. Hence a wavelength associated with any particle of such type can be directly measured using an interferometer. This applies also to massive particles such as neutrons.
From the measured wavelength and speed of photons, what is conventionally called a "frequency" can be calculated in the usual way:
where c is the speed of light ( c in a vacuum, or less in other media), f is the frequency and λ is the wavelength.
Regarding the interpretation of these quantities, Feynman provided the following advice: [1]
We cannot say whether light is particle or wave. This is not an either/or situation; light seems to be both particles and waves and thus is probably neither.
Visible light shares that duality with, e.g., cold neutrons, the "frequency" of which is rarely mentioned.
Layzeeboi ( talk) 07:36, 12 February 2017 (UTC)
Hello fellow Wikipedians,
I have just modified one external link on Frequency. Please take a moment to review my edit. If you have any questions, or need the bot to ignore the links, or the page altogether, please visit this simple FaQ for additional information. I made the following changes:
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@ Boppennoppy: Hi, see it implicitly means 1 event, and 1 here is full of meaning, but (number of) event has no dimension, because it is a number. So Hertz not means "one per second", but it means "one event per second", i.e., one (or 1) here, is full of meaning. Hertz does not mean 1 "kilometer" per second or one "kilogram" per second or anything else, it means one "event" per second. Hooman Mallahzadeh ( talk) 16:14, 30 December 2021 (UTC)