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## How many photons are reflecting?

 Yes third only, sorry for language mistakes.
No worries: we are all very skilled communicators so we can compensate as I'm sure you do when someone tries to talk to you in your first language when they are not used to it... well most of us anyway. Your skills are better than a lot of native English speakers I've met ;)

 This also would give me some info I was looking by asking indirect question like one at the beginning of this thread.
It is better to be direct - especially when you are talking to scientists. You will get much better help a lot sooner. Don't worry about appearing silly or anything - we've all been there: we understand.

ZapperZ has given you a good lead to follow. Enjoy :)

Mentor
 Quote by Alvydas But if photon is a point it can not overlap each other and therefore always acts alone on an atom.
First, as I said above, it is bad to think of a photon as a classical point particle, which appears to be what you are describing. However, because an atom does have size even if photons do not you could still get multiple photons interacting with the same atom at a given time.

 Mentor Blog Entries: 27 Furthermore, the multiphoton effect has nothing to do with the "size" of the photon, but rather the time scale of the interactions. In multiphoton photoemission, it is the time for an excited state to decay back to its ground state. If a photon can excite a particular electron while it is in an excited (but bound state) of the solid before it decays back to the valence band, then it has a chance to be excited to an even higher state. The factor that affects this includes the photon density per unit area, and the decay rate of the excited state. It has nothing to do with the size of the photon. Zz.
 So I can send strong infrared beam to a mirror and get reflected visible light ? But not due surface heating, just because of reemitting photons with double energy by the mirror. Am I right? If so what (approximately) power of incoming laser light I need to have at 1 square mm of mirror's surface? (to be effect visible)
 Recognitions: Gold Member Science Advisor You are referring to Laser Up-converting, which is a process that can be used successfully. Google it - there are a lot of links. Most lasers work with a single 'pumping' wavelength applied and a longer wavelength laser light is produced as atoms return to a lower state. However, it is possible to pump some lasers with more than one wavelength and the resulting EM will have a higher energy than either of the pumping sources because the atoms are pumped to a level equal to the sum of the energies. This will only happen under rare circumstances where the probability of an atom that has already been 'pumped' once, will decay is less than the probability that another incoming photon will pump it further. In most circumstances, the once-excited atom will decay before this can happen.

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Blog Entries: 27
 Quote by Alvydas So I can send strong infrared beam to a mirror and get reflected visible light ?
That has not been shows to can occur. You are applying different physics to different phenomenology. The multiphoton effect is on a photoemission phenomenon, NOT a "reflection".

There's just something not quite right with what you are thinking and with your question.

Zz.

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Gold Member
 Quote by ZapperZ That has not been shows to can occur. You are applying different physics to different phenomenology. The multiphoton effect is on a photoemission phenomenon, NOT a "reflection". There's just something not quite right with what you are thinking and with your question. Zz.
Yes, I agree it's a bit tenuous but, there again, when light is reflected in a mirror, the interaction isn't just one photo - one atom, in any case, but with the bulk material. Perhaps that should have been emphasised more earlier on.
I thought this up-conversion laser effect occurred in the solid state so the effect would be not 'specular' reflection but would still involve light coming off a surface when illuminated with two other, longer, wavelengths.

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 Quote by Alvydas So I can send strong infrared beam to a mirror and get reflected visible light ? But not due surface heating, just because of reemitting photons with double energy by the mirror. Am I right?
Not to my knowledge, no. Reflection has little, if anything, to do with atomic emission.

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Blog Entries: 27
 Quote by sophiecentaur Yes, I agree it's a bit tenuous but, there again, when light is reflected in a mirror, the interaction isn't just one photo - one atom, in any case, but with the bulk material. Perhaps that should have been emphasised more earlier on. I thought this up-conversion laser effect occurred in the solid state so the effect would be not 'specular' reflection but would still involve light coming off a surface when illuminated with two other, longer, wavelengths.
I didn't want to get into that because the OP has a lot more issues with other basic understanding.

It is my opinion that this thread is nothing but a jumble of disconnected information that the OP has no ability to process correctly. This is one of those times where I often wish that people would ask just simple, basic question first before attempting to find something beyond what they are capable of understanding.

Zz.

 Recognitions: Gold Member Science Advisor Yep. I agree entirely. I think people are reluctant to ask the most basic questions for fear of appearing ignorant.
 Thank you all. I have got some useful info. I will try to adjust my style of asking to be more clear.