Exploring the Mystery of Disappearing Photons in a Sealed Box"

[Quick Karl]

If you had a perfectly sealed box that did not absorb energy, and was a perfect mirror on the inside, and you fired a stream of photons through a photon sized hole in the side of the box such that they would not reflect (bounce) back out through the hole, and you placed a photon detector inside the box, why do the photons disappear the instant you close the hole?

If photons are particles shouldn't they be trapped inside the box and detectable (seeable) forever?

 

[Vanadium 50]

What makes you think they wouldn't stay there forever? (Well, until you destroyed them by detection)

 

[Quick Karl]

By simply seeing a photon (detecting if your eyeball is a photon detector in the visible range), you destroy it?

 

[Vanadium 50]

Yes - your eye absorbs it.

 

[Quick Karl]

So, a photon is not a particle then...

I am seeking something more than the typical classroom answer.

Back to the original question -- if photons were trapped inside the theoretical perfect mirrored box, it would be light in there forever, presuming we shot visible photons in...

 

[Cthugha]

So, a photon is not a particle then...

Your idea of what the meaning of the term "particle" in physics is, seems to be way off. In a nutshell particles can only be created or annihilated in discrete amounts. The term "particle" does not imply particles are like tiny balls or something.

Back to the original question -- if photons were trapped inside the theoretical perfect mirrored box, it would be light in there forever, presuming we shot visible photons in...

It is not a realistic scenario as the photon gas and the walls will be at different temperature and will tend to thermalize, but for the sake of the simple scenario: if you managed to realize the unphysical case of a perfectly sealed box filled with mirrors which only reflect and do not absorb or transmit anything and if the photon number is so low that interactions with the vacuum state do not take place, the photons will stay inside the box forever.

However, please note that the assumption of that perfectly reflecting box is already unphysical.

 

[Vanadium 50]

So, a photon is not a particle then...

One of the least efficient ways to learn is to post a bunch of incorrect statements and wait for someone to correct them. We discourage that approach here.

 

[harrylin]

So, a photon is not a particle then...

I am seeking something more than the typical classroom answer.

Back to the original question -- if photons were trapped inside the theoretical perfect mirrored box, it would be light in there forever, presuming we shot visible photons in...

In the classroom I was taught that a photon is a "wave packet"; that's certainly not perfect, but I find it better than "particle" which leads to lots of misunderstandings. However, "wave packet" also has another meaning, notably in QM; thus both terms can be misunderstood. I guess that there is just a lack of English words...

(compare http://dictionary.reference.com/browse/particle?s=t :
Physics .
a. one of the extremely small constituents of matter, as an atom or nucleus.
b. an elementary particle, quark, or gluon.
c. a body in which the internal motion is negligible. )

PS I forgot: Welcome to Physicsforums

 

[RedSonja]

Maybe Quick Karls question simply leads back to our (current) lack of ability to comprehend the meaning of wave-particle dualism...?

 

[ZapperZ]

Maybe Quick Karls question simply leads back to our (current) lack of ability to comprehend the meaning of wave-particle dualism...?

Current formalism of quantum mechanics has no such "lack of ability". What we have trouble doing is trying to shoehorn such formalism in outdated classical analogues. People are asking the photon to be described in ways it isn't.

Zz.

 

[RedSonja]

Current formalism of quantum mechanics has no such "lack of ability". What we have trouble doing is trying to shoehorn such formalism in outdated classical analogues. People are asking the photon to be described in ways it isn't.

Zz.

I find that there's a basic difference between what we are able to describe mathematically and what we are able to comprehend. Inevitably this will lead to an abundance of stupid and/or strange questions seen from the photons perspective :-)

 

[harrylin]

I find that there's a basic difference between what we are able to describe mathematically and what we are able to comprehend. Inevitably this will lead to an abundance of stupid and/or strange questions seen from the photons perspective :-)

:tongue2:

 

[Chopin]

The most extreme idealization that you can make of this scenario is a single photon in a perfectly reflective box. That corresponds to the basic QM problem of a single particle in an infinite potential well, which is covered in pretty much every introductory textbook. The answer is that yes, once inside the particle will just keep bouncing around forever. You can see that by solving the time-dependent Schrodinger Equation for an infinite potential well.

However, if you put a detector in the box, that means you are putting something in the box which will interact with the photon. In this case, the photon will hit the detector and be absorbed. More precisely, it will be converted into the energy which is necessary to trip your detector, whatever that may be.

The bottom line is that the photon acts like a particle in some ways, but in other ways it does not. Specifically, it does not necessarily live forever the way that a particle does--by interacting with another object, it can be absorbed, after which there is nothing left in the box. Until that point, though, it will indeed keep bouncing around.

 

[Quick Karl]

Excuse me, gentlemen,

I should have known better than to ask a question on an internet forum -- it seems always to bring out the best in people...

Nevertheless, the question still remains unanswered, unless you consider quips, sound bites, and insults, to be answers.

Vanadium50, if I am too far below your vast intellect, please, feel free to delete my account immediately.

 

[Quick Karl]

Chopin,

Thank you. At least I have a path to follow now...

 

[Vanadium 50]

I should have known better than to ask a question on an internet forum -- it seems always to bring out the best in people...

Asking a question is not the same as making a statement. The former usually works better if you want an answer.

 

[harrylin]

Excuse me, gentlemen,

I should have known better than to ask a question on an internet forum -- it seems always to bring out the best in people...

Nevertheless, the question still remains unanswered, unless you consider quips, sound bites, and insults, to be answers.

Vanadium50, if I am too far below your vast intellect, please, feel free to delete my account immediately.

Sorry too: I thought that post #2 already already answered your question (and you failed to engage :uhh:). But now that I read it again, I realize that it may have been not that clear for you, so that you perhaps did not understand that it was a serious reply!