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Energy Of A Single Photon In Em Radiation?

by Robin*
Tags: energy, photon, radiation, single
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Robin*
#1
Aug29-13, 12:43 PM
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Is the energy of all photons in em radiation same? That is, say light differs from radio waves only in the number of photons per second
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analogdesign
#2
Aug29-13, 12:45 PM
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No, the energy of a photon is proportional to its frequency. That is one reason why gamma radiation is dangerous but radio waves are harmless.
Robin*
#3
Aug29-13, 01:12 PM
P: 9
How can a single photon have frequency? Imagining a single photon travelling sinusoidally(?) it does not make sense to think that its energy has got anything to do with the sine wave. How can its energy vary just depending on its path?

Nugatory
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Aug29-13, 01:22 PM
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Energy Of A Single Photon In Em Radiation?

Quote Quote by Robin* View Post
How can a single photon have frequency? Imagining a single photon travelling sinusoidally(?) it does not make sense to think that its energy has got anything to do with the sine wave. How can its energy vary just depending on its path?
It may not make sense, but that's still the way the world works. The most convincing evidence of this was discovered around the end of the 19th century (google for "photoelectric effect einstein").

EDIT: The photon most certainly does not travel a sinusoidal path. But it still has a frequency and that frequency is proportional to its energy.
jtbell
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Aug29-13, 01:42 PM
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Quote Quote by Robin* View Post
Imagining a single photon travelling sinusoidally(?)
No, photons do not travel in sinusoidal paths. Neither do electrons or other particles, which also have a "wave function" associated with them. There is no generally accepted answer to what this wave function "really really is," with the result that half the threads in our Quantum Physics forum are related to this puzzle. All we know for sure is that we can define this wave function, and do certain mathematical operations on it to predict the results of experiments very successfully, in a statistical sense at least.
Robin*
#6
Aug30-13, 04:49 AM
P: 9
1.Imagining some kind of wavy pattern are there 2 streams of photons moving perpendicular to each other?or is it merely after hitting an electron that it induces E and B?

2.Why would photons move in wavy pattern at all,cant they move in a straight line?
ZapperZ
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Aug30-13, 05:41 AM
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Quote Quote by Robin* View Post
1.Imagining some kind of wavy pattern are there 2 streams of photons moving perpendicular to each other?or is it merely after hitting an electron that it induces E and B?

2.Why would photons move in wavy pattern at all,cant they move in a straight line?
Did you even read the post right before this by jtbell? Only you think that photons move in a "wavy pattern".

Zz.
f95toli
#8
Aug30-13, 05:43 AM
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Photons do not move in a "wavy pattern". That said, we can't really say anything about HOW they move. Photons are fundamentally quantum mechanical "objects" and it is not possible build up any inutition about how they "really" move, or even what they are (the same can be said about just about everything else as well).

We have extremelly good mathematical models, so the problem is NOT that we do not understand what photons are. But what these models describe is so different from our everyday macroscopic world that it is extemely difficult to get any inuitive grasp of them
Robin*
#9
Aug30-13, 07:21 AM
P: 9
Quote Quote by f95toli View Post
Photons do not move in a "wavy pattern". That said, we can't really say anything about HOW they move. Photons are fundamentally quantum mechanical "objects" and it is not possible build up any inutition about how they "really" move, or even what they are (the same can be said about just about everything else as well).

We have extremelly good mathematical models, so the problem is NOT that we do not understand what photons are. But what these models describe is so different from our everyday macroscopic world that it is extemely difficult to get any inuitive grasp of them
I was having that picture of perpendicular electric and magnetic fields in mind...what do they actually mean?

Cant we make a common sensical assumption that they( or the wavefunction that represents it) move in a straight line.
Robin*
#10
Aug30-13, 07:32 AM
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Quote Quote by ZapperZ View Post
Did you even read the post right before this by jtbell? Only you think that photons move in a "wavy pattern".

Zz.
I am sorry if had hurt your sentiments regarding photon...
DaleSpam
#11
Aug30-13, 07:43 AM
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Quote Quote by Robin* View Post
Cant we make a common sensical assumption that they( or the wavefunction that represents it) move in a straight line.
No. There are many instances where that can be experimentally demonstrated to be false. Even a single slit experiment will get photons travelling in bent lines, and two slit or gradient experiments can show that a single photon travels along multiple paths.
ZapperZ
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Aug30-13, 07:44 AM
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Quote Quote by Robin* View Post
I am sorry if had hurt your sentiments regarding photon...
(Scratches head)

Er..... Alright then!

But you still didn't answer the question. It is hard to know if you just didn't read the responses you've been given, or you didn't understand what you read. It has nothing to do with "hurt sentiments", whatever those are.

Zz.
Robin*
#13
Aug30-13, 08:53 AM
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Quote Quote by ZapperZ View Post

But you still didn't answer the question. It is hard to know if you just didn't read the responses you've been given, or you didn't understand what you read. It has nothing to do with "hurt sentiments", whatever those are.

Zz.
Yes I have read it.I made the mistake of thinking of frequency as only the number of particles passing through a point for a while.
Robin*
#14
Aug30-13, 08:59 AM
P: 9
What does that common representation of em wave as perpendicular electric and magnetic field imply?

Is there any particular order of emission that is radio waves, microwaves etc in that order or are they emitted randomly?
jtbell
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Aug30-13, 09:03 AM
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Quote Quote by Robin* View Post
What does that common representation of em wave as perpendicular electric and magnetic field imply?
It means that if you "shine" an electromagnetic wave on (say) an electron, it exerts electric and magnetic forces on the electron.

Is there any particular order of emission that is radio waves, microwaves etc in that order or are they emitted randomly?
What do you mean by "order of emission?"
DaleSpam
#16
Aug30-13, 09:11 AM
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Quote Quote by Robin* View Post
What does that common representation of em wave as perpendicular electric and magnetic field imply?
Classically an EM wave is a propagating EM field in which the electric and magnetic fields are mutually perpendicular and perpendicular to the direction of propagation. That is the classical picture, but you really shouldn't mix the classical and quantum pictures.

Quote Quote by Robin* View Post
Is there any particular order of emission that is radio waves, microwaves etc in that order or are they emitted randomly?
I don't know what you are asking here. Radio waves are low frequency, microwaves are slightly higher, infrared is higher than that, then visible light, ultraviolet, x-rays, and gamma-rays. Their emission is not random, but the way you phrased the question is confusing.
Robin*
#17
Aug30-13, 10:08 AM
P: 9
So there is only one stream of photons and no perpendicular streams ?
What I meant by order of emission is, is there some process sequentially producing photons of different frequency according to em spectrum? or are photons of different frequencies being produced at random?
DaleSpam
#18
Aug30-13, 10:18 AM
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Quote Quote by Robin* View Post
What I meant by order of emission is, is there some process sequentially producing photons of different frequency according to em spectrum?
You could do a frequency sweep, but this would typically be done with RF where the quantum mechanical description (photons) is not terribly helpful and you are generally better sticking with a classical description.

My personal recommendation is that it seems like you should learn classical EM before attempting to learn quantum electrodynamics.

Quote Quote by Robin* View Post
or are photons of different frequencies being produced at random?
It might help if you identified the system you are interested in. The mechanism for producing photons is different if you are talking about a radio antenna, an incandesent light, an x-ray tube, or a flourescent substance.


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