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Based on the H-165 entry in Sutton's work (to see it, click on the link
provided by Michael A Thomason,
<http://physicslearning.colorado.edu/PIRA/Sutton/PARTIII.pdf> and search
the document for "H-165" to find the entry "H-165. Radiometer Effect and
Convection." on page 50 of the document)
the word "radiation" in the abstract
Put a hot metal object in a smoke filled projection cell and
the smoke will be repelled by radiation pressure. Convection
will cause an upward clearing.
<http://www.physics.ncsu.edu/pira/4therm/4B50.html> should be replaced with the word "radiometric."
Based on my understanding of how a radiometer (see
works, the side of a smoke particle facing the hot metal object is
heated up by the electromagnetic radiation from the hot object. That
side is therefore hotter than the other side of the smoke particle and
is thus transferring energy at a greater rate (than the other side is)
to the air in contact with it. As such the hotter side of the smoke
particle must be transferring momentum (directed toward the hot object)
at a greater rate than the other side is transferring momentum (directed
away from the hot object) to the air in contact with that side. By
Newton's third law, the net rate at which momentum is being transferred
to the smoke particle by the air is non-zero and is directed away from
the hot object. As a result, the smoke particle is moving away from the
From: email@example.com [mailto:phys-l-
firstname.lastname@example.org] On Behalf Of Bernard Cleyet
Sent: Wednesday, May 30, 2007 10:30 PM
To: Forum for Physics Educators
Cc: Nancy Seese
Subject: Re: [Phys-l] E-M radiation pressure
I guess I must go back to reading school. Appeared clear to me:
4B50.62 radiation and convection H-165 Put a hot metal
object in a smoke filled projection cell and the smoke will be
repelled by radiation
pressure. Convection will cause an upward clearing.
Radiation repels smoke was what I questioned.
bc, thinks Michael is a bit huffy.
p.s. If it's true (Such IR radiation will repel smoke.), please
explain. BTW I couldn't find the projection cell demo. Which page?
Michael A Thomason wrote:
PIRA makes no such claim.
Your quote, below, is a reference in the PIRA Demonstration
http://physicslearning.colorado.edu/Pira.asp, to Richard Sutton'sclassic,
1938 "Demonstration Experiments in Physics".Bibliography;
The entire text of Sutton's work is online and linked from the
by clicking the link included in this reference, you could have readhis
entire (suspect) demo number H-165 herenone&pa
Director of Physics Learning Laboratories
University of Colorado Boulder Department of Physics
Forum for Physics Educators