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Re: If a photon has polarization.



Qiang Liu
As far as I know, polarization is not an emergent or statistical property.
So I take it that what I think I know of ensembles applies as well to
individuals.
While it may not be posible a priori to associate a polarization angle to
a photon in flight, without
imposing some test - thereafter, the state is known.
So to answer the questions as well as I can:
1 a camera detects a stray photon.
2) It detects a photon passing two aligned polarizers with some fair
probability
3) it does not detect a photon passing two non aligned polarizers, with
some high probability.

Brian

At 21:29 5/12/02 +0800, you wrote:
Dear friends

I have some questions about the polarization of light. From classical Mexwell
Equation, one can give out a electromagnetic wave with polarization. And
visible
lights has polarization as well. However, one can not say that a photon
has polarization.

Spin is the property of photon to substitute polariztion in the field theory.
However, I still cannot understand why visible lights has polarization,
but a visible
photon has not.

Let's think out a ideal experiment:
There are three tubes, each one has a film in its bottum. Two of these
tube have

polarization foils (PF). I mark them 2 and 3. The polarization foils in 2 tube
are parallel, while the polarization foils in 3 tube are vertical.
'Parallel' means
the parallel of polarization, the same of 'vertical'.



----------------------------------|
| 1
----------------------------------|

film

--------|----------------|--------|
| | | 2
--------|----------------|--------|

| | film


--------|----------------|--------|
| | | 3
--------|----------------|--------|

| \ film

They are put into a dark room, i.e. a vacuum of lights. However it is not
absolute
vacuum of lights. After a week, there may be a photon enters a tube and
reach the film
in tube 1. The question is that, after several monthes, can some photon
reach the
film in 2 and 3 tubes?