RE: Crooke's Radiometer

["Levin, Robert" <robert.levin@sylvania.com>]

Quantitative measurements, especially in the infrared, were made well into
this century using instruments where vanes were suspended by a fiber that
produced a restoring torque, and deflection was measured as in the light
beam galvanometer.  Thus - "radiometer."   As far as I can tell by a brief
survey, this development followed directly from the Crookes Radiometer.

The Nichols radiometer was considered a reliable instrument in the 1890s.
Tracing back a few citations from older physics books, it appears that the
operating principle was commonly recognized.  

Robert E. Levin, Ph.D.
Corporate Scientist
OSRAM SYLVANIA
71 Cherry Hill Drive
Beverly, MA 01915
phone: (978) 750-1594
fax:      (978) 750-1794
e-mail:  robert.levin@sylvania.com   
 


> -----Original Message-----
> From:	Bernard L Cohen [SMTP:blc+@pitt.edu]
> Sent:	Tuesday, April 06, 1999 11:53 AM
> To:	Multiple recipients of list
> Subject:	Re: Crooke's Radiometer
> 
> 
> 
> On Tue, 6 Apr 1999, Otto G. Raabe wrote:
> 
> > April 6, 1999
> > Davis, CA
> > 
> > Maybe it is called a radiometer because (1) it responds to
> electromagnetic
> > radiation in the form of light and especially infrared radiation, and
> (2)
> > it was named before the discovery of ionizing radiation.
> 
> 	-I would bet that it was meant as a demonstration of radiation
> pressure, the fact that radiation has momentum, and sometime later
> somebody noticed that the rotation was in the wrong direction for that
> explanation.
> 
> > 
> Bernard L. Cohen
> Physics Dept.
> University of Pittsburgh
> Pittsburgh, PA 15260
> Tel: (412)624-9245
> Fax: (412)624-9163
> e-mail: blc+@pitt.edu
> 
> 
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