🚀 go-pugleaf

In article <4b6nep$gu3@ixnews2.ix.netcom.com> Alan \"Uncle Al\" Schwartz <uncleal0@ix.netcom.com> writes:
>From: Alan \"Uncle Al\" Schwartz <uncleal0@ix.netcom.com>
>Subject: Re: How Does a Radiometer Work?
>Date: 19 Dec 1995 15:58:17 GMT

>Reasonable intensities of light have insufficient momentum to 
>meaningfully drive small surface areas of large mass.

>The radiometer is under a light vacuum.  Heating of the black side of 
>each vane launches mass convection currents with sufficient orthogonal 
>component to drive the vanes.

Theres a bit more to it than that. A light vacuum means theres still many 
molecules of air in the err air. The light raises their kinetic energy, 
however this will have equal effect on both sides of the vane. 

The silvered side reflects most of the visible spectrum. The black side is a 
poor reflector and absorbs the light/radiation. Hence the increase in surface 
temperature and consequential increase of the small oscilations/vibrations of 
surface molecules of the black side.

Now the colisions of energised air molecules with energised surface molecules 
of the black side has many effects, one of them being the absorbtion of the 
kinetic energy due to colisions by the bulk of the vane, billions of these 
collisions going on results in gradual recoil of the vane.

>The obvious experiment is to erect the system on a vacuum line with a 
>good dynamic pressure gauge, illuminate with constant intensity light, 
>and use a strobe or rpm counter to graph rotational velocity vs pressure. 
> Add a variety of gases for different molecular weights, and you have a 
>spiffy publication for J. Chem. Ed.

And what was the question? I missed the begining of this thread.

>Alan "Uncle Al" Schwartz
>uncleal0@ix.netcom.com  ("zero" before "@")
>http://vvv.com/adsint/freehand/uncleal/

Tejay M Sener
m8904850@redback.co.rmit.edu.au