Frequency of a photon

[Jacques]

Hi I have a little question that is bugging me:

If time freeze at the speed of light, how is it possible for light to have a frequency other than 0 ?

[lepidoptera]

the world may never know.... seriously, I am only 13, I havent learned about this yet. Can you explain? And don't use baby words. i'm NOT a baby. I am as intelligent as a 26 year old man

[Jacques]

Do you know about relativity ?

Time dilatation ?

[timo]

Most 26 year old men know that getting an answer in an internet forum can take longer than 3 minutes.

On topic: The frequency is given in units of coordinate time (which directly leads to frequency being dependant on the coordinate system) not in units of the Eigentime (which would be the time measured by the photon and which would indeed be kind of freezed).

[YT2095]

Light always has a frequency, when it has No frequency, it`s called a Magnet

 

if you match the Velocity (not the same thing and also impossible) unless you`re at the same Frequency also (impossible) it`ll still have one

 

beyond this is pure speculation, in fact I may have even stepped into that realm myself with this answer.

[Jacques]

The frequency is given in units of coordinate time (which directly leads to frequency being dependant on the coordinate system) not in units of the Eigentime (which would be the time measured by the photon and which would indeed be kind of freezed).

The definition of frequency I learn at school is number of cycle per unit of time. Can you explain me or direct me to some reading about the definition of frequency as a unit of coordinate time ?

Also I don't understand the Eigentime word...

Thanks

[Jacques]

My intuition tells me that when light travel it doesn't vibrate, only when you mesure it that you see a vibration..

[YT2095]

that implies it "Knows" when you`re "Looking" at it.

 

light does indeed oscillate up-down, side to side, and all other dirrections too (that`s how a polarised film can work) and the reason we see different colors

[Jacques]

Yes it knows when you look at it because it interact with the matter of the detector (eyes, polarizer, photographic plate , CCD... )

I like when you say "when it has No frequency, it`s called a Magnet "

[timo]

About Eigentime:

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Generally, the position of a paticle is given as position as a function of time P(t). In Relativity this is replaced by a trajectory in spacetime. Let A and B both lie on this trajectory and B be in the future of A:

 

- In any coordinate system A and B are defined at a certain time t(A) and t(B), respectively. The coordinate time it takes for the particle to travel from A to B is dt=t(B)-t(A), then. This is a quantity that depends on the chosen coordinate system.

 

- But there´s also a quantity that´s independent on any chosen coordinate system: The length of the trajectory between A and B (draw a line on a piece of paper, the lenght of the line won´t change if you rotate the paper). This quantity is called Eigentime because it is the coordinate time difference you´d get if you were measuring the coordinate time in the particle´s frame of rest.

 

- Now, because the metric in Minkowski-space is not positive definite (in fact, calling it metric isn´t even correct - it should be called pseudo-metric but physicists are lazy people) you can have connecting lines between two non-identical points A and B that have a length of zero. The trajectories of massless particles are such trajectories. That´s why their Eigentime between any two points is zero.

 

btw.: One thing that just came to my mind: Perhaps it helps you to know that Eigentime is a german word (but it´s also the term used in english) which means "[the particle´s] own time" or simply the time measured by the particle itself (as said above).

 

 

About the freezing time and the "cannot oscillate in no time":

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I find this rather hard to explain in detail so I´ll try the "why this argument is not valid"-method. There is no frame in which the photon is at rest. Furthermore, there is no coordinate system in which the coordiante time between any to nonidentical points on the photon´s trajectory is zero. This leads to the result that the "time freezes" scenario can not happen when you speak about coordinate time. And to come back to my initial statement: Frequency is given in units that do not lead to problems.

 

EDIT: Oh, and what you call "time" is the coordinate time - the time measured in the coordinate system you are using.

[YT2095]

I like when you say "when it has No frequency, it`s called a Magnet "

 

a photon at "DC" (for wants of a better term) is that which emminates from a stationary magnet, at Oscillation it becomes an EM Wave, at Really High frequencies it becomes a color that you see.

 

if you had a simple bar magnet and could wave it at 27.78125 million times per second, you`de be sending a dead carrierwave over chan 19 on UK CB for instance

[Jacques]

My initial idea was: At the speed of light time freeze. Photon move at the speed of light. Each photon have frequency. n/t ???

Solution: An other time dimension is needed, not affected by time dilatation.

That´s why their Eigentime between any two points is zero.

How can the frequency be stored in a photon without Eigentime (0) ?

Maybe it doesn't need to be stored when Eigentime is 0 Ah! ah!

Still need to transmit from point A to point B. Maybe we must forget to speak of photon in terms of frequency but speak of it in term of energy that doesn't have a time conotation..

[timo]

My initial idea was: At the speed of light time freeze. Photon move at the speed of light. Each photon have frequency. n/t ???

Solution: An other time dimension is needed' date=' not affected by time dilatation.

[/quote']

No, Solution: Express the frequency in a time that cannot freeze. Actually I was hoping that at least this point of my post was easy to understand.

 

How can the frequency be stored in a photon without Eigentime (0) ?

Oscillations per coordinate time.

 

Maybe we must forget to speak of photon in terms of frequency but speak of it in term of energy that doesn't have a time conotation..

[Severian]

Hi I have a little question that is bugging me:

If time freeze at the speed of light' date=' how is it possible for light to have a frequency other than 0 ?

[/quote']

 

Since the photon doesn't have a rest frame, the question is not very well defined. In other words, time doesn't freeze in the photons rest frame because it doesn't have one!

 

However, you can get a semi-hand-waving insight into your question by thinking about a 'massive photon' approaching the speed of light. That is, consider a photon like object which has a very very small mass and therefore a speed just below c. That will indeed have a rest frame, and from our perspective (as you say) time will appear to pass very slowly for the 'photon'. However, in its own rest frame, time will be passing normally (indeed, it would see our time passing slowly!) so it can have a frequency just like it normally has.

[insane_alien]

here is a simple way of putting it (not baby speak if you are so insecure about that i mean in the basics of physics) i take it that you know that light also behaves as a wave and tat a photon can be thought of as a packet of waves. to find the frequancy all you have to do is count the crests that pass a certain point in a fixed amount of time. work out the number of crests per second and there you have it that is the frequency. relative to the [photon the frequency would be zero as the "wave" could not go towards the front of the photon as this would be traveling FTL. but to an outside observer traveling at a different velocity it would appear to have a frequency. i hope that this is adequate to solve your question. (i know how you feel about getting talked down to.)

[Obnoxious]

I thought everything had a frequency...

Ya know, that good old H bar over momentum dealie.

[entropydave]

the world may never know.... seriously, I am only 13, I havent learned about this yet. Can you explain? And don't use baby words. i'm NOT a baby. I am as intelligent as a 26 year old man

Oh, well that's ok then... please note, not a "25 year old man", or "a 27 year old man" (or indeed woman) but a "26 year old man"

...sounds like the sort of thing a 13 year old would say!

[Ophiolite]

I am as intelligent as a 26 year old man

In 13 years, when you look around you, you'll find that was nothing to boast about. . Thanks for asking the question: I learnt a good deal from the replies.

[swansont]

I thought everything had a frequency...

Ya know' date=' that good old H bar over momentum dealie.[/quote']

 

h/p is wavelength