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Q & A: photon identity

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Most recent answer: 03/21/2008
Q:
If a photon strikes an object that we see as green (or any other 'color') is the photon that impinges our optical nerve the SAME (in any sense) photon as the one that struck the object?
- Ric (age 67)
Lake Villa IL
A:
Tough question. I would say, ordinarily, no. The reason is that ordinary light beams can't be thought of as collections of individual photons. In fact, they aren't even close to having a definite number of photons in them.
There are special sources in which nearly definite numbers of photons (e.g. one) are emitted. In those cases, if the light bounces off some surface, I think it would make sense to say that the same photon that bounced was later seen.

Mike W.


(published on 03/21/2008)

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