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Re: [Phys-l] radio vs. light



I do NOT intend to defend this Sciam article- it is criminally stupid
in its utterances. But if you look at the author's applications of
statements like "Radio signals interfere with each other but photons
do not", you see that he is referring (at least part of the time) to
situations in which two pencil beams of light cross each others path,
perhaps on the way to separate detectors. There is no interference
between the two beams - ie., neither detector can tell that its
received signal was crossed by another light beam. (Of course if the
two beams were brought together onto a single detector, interference
effects would arise.)

Of course the same thing would be true of crossed pencil beams of
radio waves. The difference is simply that the much longer
wavelengths of radio waves typically precludes such spatially
restricted pencil-like beams, and both beams typically spread out to
influence both detectors.

I don't think the author understands this - he seems to believe in
some more fundamental (and fictional) difference between light and
radio radiation.


Bob Sciamanda
Physics, Edinboro Univ of PA (Emeritus)
www.winbeam.com/~trebor
trebor@winbeam.com
----- Original Message -----
From: "JMGreen" <jmgreen@sisna.com>
To: "Forum for Physics Educators" <phys-l@carnot.physics.buffalo.edu>
Sent: Thursday, July 19, 2007 3:11 PM
Subject: Re: [Phys-l] radio vs. light


|
| >Radio signals interfere with each other but photons do not.
| >Out of phase radio waves can cancel each other out, but
"destructive
| >interference is impossible with light."
|
| In the phrase of a Cave Man TV ad "What???"
|
| We have no idea what light "is," but we sometimes model it as
| "photons." But if light is modeled as photons so can radio "waves"
| -- they seem to be the same animal.
|
| >And "destructive interference is impossible with light"? Good
grief.
|
|
| Jim
|
|
|
| J M Green
| Email: MailTo:JMGreen@sisna.com
| WWW: HTTP://users.sisna.com/JMGreen
|
| _______________________________________________
| Forum for Physics Educators
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