Talk:Frequency
From Wikipedia, the free encyclopedia
 |
This article is within the scope of WikiProject Physics, which collaborates on articles related to physics. | |
| ??? | This article has not yet received a rating on the assessment scale. [FAQ] | |
| ??? | This article has not yet received an importance rating within physics. | |
|
Please rate this article, and then leave comments here to explain the ratings and/or to identify the strengths and weaknesses of the article. |
||
Contents |
[edit] 440 Hz
some think thisIs it not true the A tuning note is only 440 Hz in the United States, while in fact 442 Hz in Europe? Perhaps this should be changed.
- See Pitch (music) — Omegatron 14:36, 20 February 2006 (UTC)
[edit] Changing wavelength
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?
It's correct. Suppose the wave propagates 340 metre per second in the first medium, and 680 m/s in the second, and suppose the frequency is 340 hertz so that the period (i.e. the time it takes for one complete oscillation) is 1/340 seconds. These values fit a sound (a rather deep tone) passing from air into a somewhat harder medium. Then, in air, this sound travels 1 metre per period, so the wavelength is 1 metre. In the harder medium, it will travel 2 metre in the same time, doubling the wavelength.
Put differently: Yes, frequency has an inverse relationship to wavelength in a given medium, but the constant of proportionality depends on the medium.--Niels Ø 09:35, Apr 15, 2005 (UTC)
[edit] Invariance of frequency
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)
- Because it's based on time? Theory of relativity and all that?
- I'm not sure if it's worth pointing out, but the frequency of a pre-recorded signal can certainly be changed by playing it back at a different speed. Practically, if you sample something with an incorrect sampling frequency (you think it's 48 kHz but the oscillator's actually running at 48.01 kHz), then reproduce it correctly, the frequencies will be shifted.
- Plus there are things like pitch shifters to simulate a change in frequency, though that's even less relevant. — Omegatron 21:32, 7 December 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)
- It could probably be done with wormholes. :-) — Omegatron 15:02, 18 February 2006 (UTC)
- I've heard that strong gravitation could change the frequency, so wormholes, why not :)
-
- Oh you're right! You could change frequency just by flying around at a different altitude from your observer. Gravity Probe A was exactly that. — Omegatron 02:22, 7 June 2006 (UTC)
-
-
- This is a Doppler effect. GoldenBoar 16:13, 7 June 2006 (UTC)
-
-
-
-
- I don't think so. Time flows at a different speed depending on your distance from the Earth or another body. If you took a huge loudspeaker and put it in a hot air balloon, time would pass at different rates for you and the speaker, so the frequency would be shifted, since frequency is really just another word for time. — Omegatron 23:21, 7 June 2006 (UTC)
-
-
- What about the Invariance of Speed, with regard to a constant medium? The above discussion and corresponding paragraph in the article both make some broad assumptions about the source of the Waves. It is also true that if the medium remains the same, speed is invariant with regard to wavelength and frequency... That is, if you have a slinky... and start sending pulses through it at a fixed speed, changing the frequency with which you initiate the pulses will only affect the wavelength, and vice-versa (i.e., frequency is NOT invariant). Representing this fact as well would probably make the article more sensible-seeming to those who really don't know anything about waves. I mean, strictly speaking, since the article is a general description of the quantity Frequency, with respect to other common quantities or terms used to describe the nature or behaviour of waves and signals - e.g., period, phase, amplitude, wavelength, cycle, etc. - this rather random statement about the Invariance of Frequency is not true, at least not without some context. - joe
[edit] Measurement
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
the thing is tha waves are not real at all they are all fake and so is the rest of the world te only lae that is real is Leeds in England.
[edit] armature winding in synchronous motors
tell me about armature winding with photographs'.
the u suck. wats up with that someone should edit it
[edit] radians per second
In my opinion, this is not a unit of frequency, but of angular frequency. --84.159.248.246 17:04, 20 November 2006 (UTC)
