Is there such thing as an anti-photon?

  • Thread starter conner.ubert
  • Start date
In summary: There is no energy at the moment of their intersection. When two photons collide, they scatter and create new photons, but there is no energy in the collision itself.
  • #1
conner.ubert
15
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Is there such a thing as an anti-photon? and if it did exist what would happen if it collided with a normal photon?
 
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  • #2
Photon and anti-photon are identical.
 
  • #3
A photon is it's own antiparticle.
 
  • #4
there is no anti photon ... some how if there is an anti photon and if they collide they end up in an explosion
 
  • #5
space girl said:
there is no anti photon ... some how if there is an anti photon and if they collide they end up in an explosion

Welcome to PhysicsForums, space girl!

You may be thinking of the proton and the anti-proton, which release a lot of energy when they meet. Photons are different particles altogether, and do not act the same.

I might suggest reading up on what is called the "Standard Model of Physics" to gain a bit more understanding on the subject.
 
  • #6
When two photons cross each other (for example when shining two beams of light across each other) is there a noticeable difference between annihilation-creation and just passing through each other?

EDIT: Hm, on second thought this might be off-topic of me? I'm not sure? Please tell me if it is, didn't intend it
 
  • #7
No I was not confusing photons with protons. Because I know that when a particle and an anti-particle collide (such as a proton and anti-proton) the immediately turn into energy such as photons and gamma radiation. And if photons are created during the collision then what would happen if they had a anti-particle collision.

Thank you for your responses. :)
 
  • #8
Drakkith said:
A photon is it's own antiparticle.

That would have been my stock answer.. but, hang on a minute...

At the quantum level, if we have two photons in anti-phase, each still has hv worth of energy. One cannot have '-hv' of energy!

So if the two are actually anti-particles, then where does the 2hv of energy go?
 
  • #9
conner.ubert said:
No I was not confusing photons with protons. Because I know that when a particle and an anti-particle collide (such as a proton and anti-proton) the immediately turn into energy such as photons and gamma radiation. And if photons are created during the collision then what would happen if they had a anti-particle collision.

Photons do not annihilate in the same manner, as you say they are in fact a byproduct of other interactions. Photons (and "anti-photons") obey Bose-Einstein statistics, and can occupy the same region of space without issue.
 
  • #10
cmb said:
At the quantum level, if we have two photons ... each still has hv worth of energy. One cannot have '-hv' of energy!
Antiparticles do not have negative energy.

This perception is perhaps based on some formal arguments introduced by Dirac regarding the "negative-energy-solutions" of his famous equation. Look at positrons (antiparticles of electrons) in bubble chambers: they have positive mass, energy and momentum.
 
  • #11
tom.stoer said:
Antiparticles do not have negative energy.

This perception is perhaps based on some formal arguments introduced by Dirac regarding the "negative-energy-solutions" of his famous equation. Look at positrons (antiparticles of electrons) in bubble chambers: they have positive mass, energy and momentum.
Exactly, but what happens to the energy of two photons, if they act as each others anti-particles and 'annihilate'?
 
  • #12
Two photons don't annihilate "to energy" b/c they carry energy which is conserved.

When two photons collide to lowest order NOTHING happens; they don't interact at all. In next-to-leading order they scatter elastically, i.e. two new photons are created. In addition there are processes (starting at a certain threshold) where other particles like electrons can be created.
 
  • #13
cmb said:
Exactly, but what happens to the energy of two photons, if they act as each others anti-particles and 'annihilate'?

Two photons in, two photons out. It is called photon scattering, a rare process that needs to be mediated by virtual charged particles (e.g. charged vector boson or quark).
 
  • #14
So, what happens to the energy of the photons during destructive electromagnetic interference?
 
  • #15
From my understanding is that nothing will happen.
 
  • #16
cmb said:
So, what happens to the energy of the photons during destructive electromagnetic interference?

The photons are not destroyed. They're simply distributed differently than they would have been in the absence of interference.
 
  • #17
Destructive interference does not mean that the photons will vanish completely, it does only mean that it's not allowed for the two photons to be detected at a certain location (they can of course be detected elsewhere).
 
  • #18
OK, so back to my question on 'does that mean negative energy'; if we go to a location where we measure destructive interference of the two photons in that location, then what energies do we measure there?
 
  • #19
Zero energy.

A detector which "sees" destructive interference in a certain place sees nothing and cannot distinguish this "nothing due to destructive interference" from "no photon at all".
 
  • #20
So is there no energy there, or is it just this type of detector that cannot detect it.

And if not, then what sort of theoretical detector could detect the energy of the two anti-phase photons at the moment of their intersection? I mean, if we had an infinitesimal electromagnetic detector, then it'd be registering 'no energy' there, right?, but we're saying there is actually 2hv there, because they head off after their encounter?

So if an EM type detector could not detect the extant energy of two anti-phase photons at the moment of their intersection, then what sort of detector can?
 
  • #21
This thread has gone completely off-topic.

Zz.
 
  • #22
ZapperZ said:
This thread has gone completely off-topic.

Zz.

Please explain?

A particle and its anti-particle are a pair that annihilate. The question is therefore whether a photon and anti-phase photon can truly and instantaneously 'annihilate' and the energy then 'reappears' (as two 'more' photons, presumably?!), or whether there is no process of annihilation and actually their presence, in proximity to each other, is simply undetectable.

So please explain why you think it is off topic? What do you understand by an 'anti-particle'?
 
  • #23
cmb said:
Please explain?

A particle and its anti-particle are a pair that annihilate. The question is therefore whether a photon and anti-phase photon can truly and instantaneously 'annihilate' and the energy then 'reappears' (as two 'more' photons, presumably?!), or whether there is no process of annihilation and actually their presence, in proximity to each other, is simply undetectable.

So please explain why you think it is off topic? What do you understand by an 'anti-particle'?

My understanding of the quantum basis of interference is simply a consequence of the probability of finding a photon (or other particle - interference in waves of cold atoms was a classic 20th century experiment) at a certain place. Where there is destructive interference, there is simply zero or near zero probability of finding a photon (or atom) at that location. Within the framework of quantum mechanics, it is no more mysterious than all those orbital shape diagrams showing where electrons are more vs. less likely to be found.

As I explained in another post, there is a phenomenon of photon-photon scattering that you could conceivably think of as photon annihilation. Normally it is treated simply as scattering, and it is very rare even for gamma rays because of the need for mediation by massive virtual charged particles. I am not even sure it has actually been observed yet.
 
  • #24
cmb said:
Please explain?

A particle and its anti-particle are a pair that annihilate. The question is therefore whether a photon and anti-phase photon can truly and instantaneously 'annihilate' and the energy then 'reappears' (as two 'more' photons, presumably?!), or whether there is no process of annihilation and actually their presence, in proximity to each other, is simply undetectable.

So please explain why you think it is off topic? What do you understand by an 'anti-particle'?

The thread has gone into the question of destructive interference. This has nothing to do with photon and its antiparticle.

Read the OP. The question has been answered within the first few posts. But somehow, it has now gone into the question of energy conservation in a destructive interference. A search of the forums will reveal that this issue has been dealt with several times.

Zz.
 
  • #25
ZapperZ said:
The thread has gone into the question of destructive interference. This has nothing to do with photon and its antiparticle.

The issue I asked/raised was whether a photon and a photon out of phase to it are each other's anti-particle - or, implicitly, if not then what 'sort' of photon is an 'anti-photon'?

It seems to me that you are drifting the thread with an unneccesary criticism, seeing as PAllen has just now provided a useful and seemingly complete response that has 'squared the circle' in regards what can happen when photons meet. (Thanks, PA, that hits the spot for me.) I don't understand what you think your additional post has added.
 
  • #26
cmb said:
The issue I asked/raised was whether a photon and a photon out of phase to it are each other's anti-particle - or, implicitly, if not then what 'sort' of photon is an 'anti-photon'?

But this isn't a photon-antiphoton issue! The interference that we know and love is a single-photon interference, not the result of a 2-photon collision! Completely different physics!

This is why I said that the thread has gone off topic!

It seems to me that you are drifting the thread with an unneccesary criticism, seeing as PAllen has just now provided a useful and seemingly complete response that has 'squared the circle' in regards what can happen when photons meet. (Thanks, PA, that hits the spot for me.) I don't understand what you think your additional post has added.

I wasn't adding anything to the thread. I was doing my responsibility as the Moderator of this forum to keep things on topic! So this is purely administrative in nature.

Zz.
 
  • #27
OK, but I still don't see why it is in error to talk about the interactions that two particles have, once they have been described as each other's anti-particle.

If it is off topic to discuss what happens when photons meet, then I've failed to grasp how photons are the anti-particles of photons, from this thread.
 
  • #28
cmb said:
OK, but I still don't see why it is in error to talk about the interactions that two particles have, once they have been described as each other's anti-particle.

If it is off topic to discuss what happens when photons meet, then I've failed to grasp how photons are the anti-particles of photons, from this thread.

It appears that you have not understood a single thing I said.

A photon, "meeting" another photon, is relevant to the thread. A photon interference, which is a SINGLE-PHOTON effect, isn't! (maybe a bold + capitalization might get through).

Zz.
 
  • #29
ZapperZ said:
It appears that you have not understood a single thing I said.

A photon, "meeting" another photon, is relevant to the thread. A photon interference, which is a SINGLE-PHOTON effect, isn't! (maybe a bold + capitalization might get through).

Zz.

I'm not aware I discussed or at all raised a single-photon interference. I have been trying to ask what happens when a photon and an anti-phase photon intersect.
 
  • #30
cmb said:
I'm not aware I discussed or at all raised a single-photon interference. I have been trying to ask what happens when a photon and an anti-phase photon intersect.

Post #14

cmb said:
So, what happens to the energy of the photons during destructive electromagnetic interference?

Zz.
 
  • #31
cmb said:
I'm not aware I discussed or at all raised a single-photon interference. I have been trying to ask what happens when a photon and an anti-phase photon intersect.

Well, I think what Zapper Z is getting at is that all inteference is a single particle phenomenon (at least since it was understood in the early 1900s that single particles can produce interference patterns). The reason why I deliberately included atoms (parenthetically) in my discussion of interference is to emphasize that interference has nothing whatsoever to do with particle/antiparticle issues - no one would claim that an atom is its own antiparticle.
 
  • #33
Thanks for the link.

Sorry, but it, and the further links from it, raise more [of the same] questions for me that are unanswered!

If photons can scatter off each other and they are anti-particles, then is that process of scattering always an annihilation-then-reemission of photons, or can they interact without annihilating, and if so what are the conditions when they do annihilate, and when they don't?
 
  • #34
cmb said:
Thanks for the link.

Sorry, but it, and the further links from it, raise more [of the same] questions for me that are unanswered!

If photons can scatter off each other and they are anti-particles, then is that process of scattering always an annihilation-then-reemission of photons, or can they interact without annihilating, and if so what are the conditions when they do annihilate, and when they don't?

You are sort of getting stuck on the words. "Annihilate" usually means that the original particles are no longer there. But fundamental quantities, like total energy or spin, are ALWAYS conserved. But there isn't much, if anything, for 2 typical photons to turn into in which those quantities are conserved. (I guess conceptually, you could have "up conversion" to a single photon.)

So generally, there is no annihilation in the sense I just defined.
 
  • #35
DrChinese said:
So generally, there is no annihilation in the sense I just defined.
Oh, OK. I can see that, but does that mean that my question/definition above was not right?

It was my assumption that 'anti-particles' meant that the particles annihilate (as in - not there any more, and their energy is transmuted somehow), and it wasn't a comment anyone picked up on, so I assumed it was right. This might be the source of my confusion.

What defines a particle as an anti-particle, then?
 
<h2>1. What is an anti-photon?</h2><p>An anti-photon is a theoretical particle that is the antimatter counterpart of a photon. It is believed to have the same properties as a photon, such as zero mass and the ability to travel at the speed of light, but with opposite charge and spin.</p><h2>2. How is an anti-photon created?</h2><p>An anti-photon can be created through a process called pair production, where a high-energy photon interacts with a strong electric field and produces an electron-positron pair. The positron, which is the antimatter counterpart of an electron, can then interact with a photon to produce an anti-photon.</p><h2>3. Can anti-photons exist in nature?</h2><p>There is currently no evidence that anti-photons exist in nature. However, some theories, such as supersymmetry, predict the existence of anti-photons in certain scenarios. More research and experiments are needed to confirm their existence.</p><h2>4. What are the potential applications of anti-photons?</h2><p>Anti-photons could potentially have applications in fields such as quantum computing and high-energy physics. They could also help scientists better understand the properties of photons and their interactions with matter.</p><h2>5. How do anti-photons differ from regular photons?</h2><p>Anti-photons have the same properties as photons, such as zero mass and the ability to travel at the speed of light, but with opposite charge and spin. This means that they would interact differently with matter and could potentially have different effects on the environment.</p>

1. What is an anti-photon?

An anti-photon is a theoretical particle that is the antimatter counterpart of a photon. It is believed to have the same properties as a photon, such as zero mass and the ability to travel at the speed of light, but with opposite charge and spin.

2. How is an anti-photon created?

An anti-photon can be created through a process called pair production, where a high-energy photon interacts with a strong electric field and produces an electron-positron pair. The positron, which is the antimatter counterpart of an electron, can then interact with a photon to produce an anti-photon.

3. Can anti-photons exist in nature?

There is currently no evidence that anti-photons exist in nature. However, some theories, such as supersymmetry, predict the existence of anti-photons in certain scenarios. More research and experiments are needed to confirm their existence.

4. What are the potential applications of anti-photons?

Anti-photons could potentially have applications in fields such as quantum computing and high-energy physics. They could also help scientists better understand the properties of photons and their interactions with matter.

5. How do anti-photons differ from regular photons?

Anti-photons have the same properties as photons, such as zero mass and the ability to travel at the speed of light, but with opposite charge and spin. This means that they would interact differently with matter and could potentially have different effects on the environment.

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