| Topic: |
Science > Physics |
| User: |
"DD@chi-town" |
| Date: |
10 Jul 2003 01:29:39 AM |
| Object: |
How many photons in a gamma ray ? |
I guess that my *real* question is: Is it possible to do an experiment
with one photon?
I was thinking about how one might make just one photon, or maybe a
very small number of them. I thought that maybe the best way is by
having one nucleus emit a gamma ray.
Is it possible to detect just one photon?
Alan
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| User: "Old Man" |
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| Title: Re: How many photons in a gamma ray ? |
10 Jul 2003 08:03:30 PM |
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<DD@chi-town> wrote in message
news:ol1qgvs38mvvkpts27aa1o2kljlnslkbg1@4ax.com...
I guess that my *real* question is: Is it possible to do an experiment
with one photon?
I was thinking about how one might make just one photon, or maybe a
very small number of them. I thought that maybe the best way is by
having one nucleus emit a gamma ray.
Is it possible to detect just one photon?
Alan
No photon detector is 100% efficient, and photo-multipliers
produce thermal electrons which are indistinguishable from photo
electrons. However, a single gamma ray can be induced to produce
a very short burst of photo electrons which can be shared amongst
several photo-multipliers, wherein the probability of a coincidence
signal arising from chance thermal electron emissions in each
detector is reduced by many orders of magnitude. Then there is the
problem of determining the incident direction of the gamma ray and
of distinguishing gamma ray events from charged particle events. In
the final analysis, it is a mater of probability, which can be high or
low, depending upon the ingenuity of the experimenter. [Old Man]
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| User: "Prateek Agrawal" |
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| Title: Re: How many photons in a gamma ray ? |
10 Jul 2003 06:00:50 AM |
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---------------------------
On Wed, 9 Jul 2003 DD@chi-town wrote:
I guess that my *real* question is: Is it possible to do an experiment
with one photon?
I was thinking about how one might make just one photon, or maybe a
very small number of them. I thought that maybe the best way is by
having one nucleus emit a gamma ray.
Is it possible to detect just one photon?
Alan
Yes it is, theoritically. Practically how would you generate a "dark room"
with no radiation is another question. There should be no radiation, not
even infra red . The enclosing chamber will emit some radiation, so that
should also be not present. I think practically it is almost impossible to
simulate.
--
---------------------------
Prateek Agrawal
Junior Undergraduate
Department Of Physics
IIT Bombay
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| User: "Jamieson Christie" |
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| Title: Re: How many photons in a gamma ray ? |
10 Jul 2003 02:58:27 AM |
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DD@chi-town wrote:
I guess that my *real* question is: Is it possible to do an experiment
with one photon?
I was thinking about how one might make just one photon, or maybe a
very small number of them. I thought that maybe the best way is by
having one nucleus emit a gamma ray.
Is it possible to detect just one photon?
It's possible to detect a single photon, even the human eye is sensitive
enough. It's more difficult to make an experiment that will create one and
only one photon. A lot of effort has gone into it recently, as it would be
very useful for quantum computation research.
Jamieson Christie
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| User: "Don Stauffer" |
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| Title: Re: How many photons in a gamma ray ? |
10 Jul 2003 09:17:12 AM |
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My memory of eye sensitivity to pulses was that it required about on
average three photons to detect pulse. Admittedly this is pretty close
to single photon measurement. However, when we are detecting single
photons, the amount of photon noise is, almost by definition, extreme,
and it depends somewhat on how you do the statistical data analysis.
And, in answer to original question, yes it is possible, and has been
for some time. However, for same reason as above, one has to use good
measurement theory and analyse results VERY carefully. Plus, do many
samples.
Jamieson Christie wrote:
DD@chi-town wrote:
I guess that my *real* question is: Is it possible to do an experiment
with one photon?
I was thinking about how one might make just one photon, or maybe a
very small number of them. I thought that maybe the best way is by
having one nucleus emit a gamma ray.
Is it possible to detect just one photon?
It's possible to detect a single photon, even the human eye is sensitive
enough. It's more difficult to make an experiment that will create one and
only one photon. A lot of effort has gone into it recently, as it would be
very useful for quantum computation research.
Jamieson Christie
--
Don Stauffer in Minnesota
stauffer@usfamily.net
webpage- http://www.usfamily.net/web/stauffer
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| User: "Eric Prebys" |
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| Title: Re: How many photons in a gamma ray ? |
10 Jul 2003 12:05:47 PM |
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Don Stauffer wrote:
My memory of eye sensitivity to pulses was that it required about on
average three photons to detect pulse. Admittedly this is pretty close
to single photon measurement. However, when we are detecting single
photons, the amount of photon noise is, almost by definition, extreme,
and it depends somewhat on how you do the statistical data analysis.
Actually, the truth is kind of interesting. As I understand it,
the receptors in the retina *are* sensitive to individual
photons, but the noice is pretty high, so there is some sort
of coincidence implemented in the optic nerves or brain that
requires "a few photons". That means that the human eye can see
a few photons, even if they don't strike the same receptor.
And, in answer to original question, yes it is possible, and has been
for some time. However, for same reason as above, one has to use good
measurement theory and analyse results VERY carefully. Plus, do many
samples.
Experiments with single photons are done all the time. For
example,Geiger counters count single photons when they're
near a gamma source.
-Eric
Jamieson Christie wrote:
DD@chi-town wrote:
I guess that my *real* question is: Is it possible to do an experiment
with one photon?
I was thinking about how one might make just one photon, or maybe a
very small number of them. I thought that maybe the best way is by
having one nucleus emit a gamma ray.
Is it possible to detect just one photon?
It's possible to detect a single photon, even the human eye is sensitive
enough. It's more difficult to make an experiment that will create one and
only one photon. A lot of effort has gone into it recently, as it would be
very useful for quantum computation research.
Jamieson Christie
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| User: "S. Enterprize Company" |
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| Title: Re: How many photons in a gamma ray ? |
10 Jul 2003 11:25:24 PM |
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Re: How many photons in a gamma ray ?
A gamma ray is a high energy photon. There are ways to isolate one gamma
ray.
and
gamma ray photon + e- ---> e- + ( particle pair creation)
The number of photons in a gamma ray I guess would be a function of time.
Shorten the time span of a gamma ray you get less photons.
S. Enterprize Co. (Membership)
http://www.s-enterprize.com/
S. Enterprize (Science Journal)
http://smart1234.s-enterprize.com/
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| User: "Gregory L. Hansen" |
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| Title: Re: How many photons in a gamma ray ? |
10 Jul 2003 09:17:30 AM |
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In article <ol1qgvs38mvvkpts27aa1o2kljlnslkbg1@4ax.com>,
<yang444@oco.net> wrote:
I guess that my *real* question is: Is it possible to do an experiment
with one photon?
I was thinking about how one might make just one photon, or maybe a
very small number of them. I thought that maybe the best way is by
having one nucleus emit a gamma ray.
Is it possible to detect just one photon?
Put enough absorbing media between the source and receiver that the
intensity is reduced almost to nothing. Then photons will be emitted
at random intervals, but with an average number of counts per quantity of
time.
--
"Is that plutonium on your gums?"
"Shut up and kiss me!"
-- Marge and Homer Simpson
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