Re: [Phys-l] E-M radiation pressure

[Bernard Cleyet <bernardcleyet@redshift.com>]

You just described the radiometry effect not radiation pressure, which 
won't work w/ a smoke particle either, as the difference in temp. 
between the two sides must be minuscule. 

bc, still not satisfied.

Jeffrey Schnick wrote:

> 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.
> found at
> <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
> <http://en.wikipedia.org/wiki/Crookes_radiometer> )
> 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
> hot object.
>
> Jeff Schnick
>
>  
>
> > -----Original Message-----
> > From: phys-l-bounces@carnot.physics.buffalo.edu [mailto:phys-l-
> > bounces@carnot.physics.buffalo.edu] 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:
> >
> >    
> >
> > > Bernard,
> > >
> > > PIRA makes no such claim.
> > >
> > > Your quote, below, is a reference in the PIRA Demonstration
> > >      
> > Bibliography,
> >    
> >
> > > http://physicslearning.colorado.edu/Pira.asp, to Richard Sutton's
> > >      
> > classic,
> >    
> >
> > > 1938 "Demonstration Experiments in Physics".
> > >
> > > The entire text of Sutton's work is online and linked from the
> > >      
> > Bibliography;
> >    
> >
> > > by clicking the link included in this reference, you could have read
> > >      
> > his
> >    
> >
> > > entire (suspect) demo number H-165 here
> > > http://physicslearning.colorado.edu/PIRA/Sutton/PARTIII.pdf#pagemode=
> > >      
> > none&pa
> >    
> >
> > > ge=1.
> > >
> > > Michael Thomason
> > > Director of Physics Learning Laboratories
> > > University of Colorado Boulder Department of Physics
> > >  303-492-7117
> > >  thomason@colorado.edu
> > >  http://physicslearning.colorado.edu
> > >
> > >      
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