Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: waytogo on 17/02/2013 23:52:42
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Someone here is able to explain something about that?
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JP would be the man for that I think :)
But it has to do with energy changes, and there is a recoil in any material letting off a photon, which imply that 'something' changed/let go, even though you can't 'see' that photon leaving. But we can see the annihilation, that's how we exist, by translating those annihilations through our senses. And you have the dualism too, wave/particle, to consider. Where one explanation fails the other comes to be.
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Basically, a photon is a wiggle in the electromagnetic field. Since electromagnetic fields are emitted by charged particles, to make it wiggle means wiggling a charged particle. Whenever a charged particle, such as an electron, accelerates, it generates photons.
There are very sophisticated quantum models for how this happens, but it all comes back to charges moving.
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Basically, a photon is a wiggle in the electromagnetic field. Since electromagnetic fields are emitted by charged particles, to make it wiggle means wiggling a charged particle. Whenever a charged particle, such as an electron, accelerates, it generates photons.
There are very sophisticated quantum models for how this happens, but it all comes back to charges moving.
Please keep in mind, everyone, that this is a handwaving argument. In reality an electrons principle quatum number correspoding to the amount of energy changes by dropping to a state of lower energy. In equantum mechanics we don't say that the electron accelerates or anthing like that. It just changes energy levels. If you find that impossible to visualize then you understand it correctly. :)
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I'm starting to think that "photon" is simply a name we give to a short burst (or quanta?) of electromagnetic radiation.
In my head, I see a theoretical electromagnetic radiation detector that is monitoring a constant "wave" of radiation. The detector doesn't do anything until it has a certain length, then it goes "bing!" and we say that it has detected a photon. So while a contstant wave is being detected, the machine is also indicating that the wave is being detected in discreet "bings" which we call photons.
This would fit with the notion that a wiggling electron would induce an electromagnetic wave, which in turn can be measured as a "photon".
Is this explanation too simplistic though?
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Myself I suspect it's trickier than that :)
It's not a wave, and it's not a photon. If it is a field then you can describe that as observer defined points filling up a 4D 'space', as we observe reality locally. Those points have a duality that we describe as waves/particles. Each 'room' defined from ones local observations. As no room is the exact same when you compare your definition of time and distance to some other 'room', and as what you observe is the reality you live in, this property is built in.
Then again, I don't really know how to define such a observer dependent 'field'?
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Bizerl: The detector doesn't do anything until it has a certain length, then it goes "bing!" and we say that it has detected a photon.
Einstein got his Nobel prize for the explaining the photoelectric effect; before this, physicists thought that light was a steady, continuous wave in the manner I think Bizerl might be describing: "It just builds up until it has enough energy."
In fact, you could imagine a single photon as a fuzzy particle - a bunch of waves that last a very short time (picoseconds or less). If this wave/particle has enough energy (ie high enough frequency) to kick out an electron from a metal in a vacuum, it will. If it doesn't have a high enough frequency, it won't kick out an electron. Shining the light for longer delivers more photons, but as the individual photons don't have any more energy, it doesn't kick out an electron no matter how long you wait.
When you get well above the level of a photon to the level of a continuous coherent laser beam, you can consider this as a steady wave that continues for a long time, but it is just made up of billions of photons, which individually obey the photoelectric effect.
For more: http://en.wikipedia.org/wiki/Photoelectric_effect#Emission_mechanism