Re: [Phys-l] Interesting Shadows

[curtis osterhoudt <flutzpah@yahoo.com>]

The halo has been touched upon many times in this mailing list. It is, again, an 
example of "the optical glory" 
(http://en.wikipedia.org/wiki/Glory_%28optical_phenomenon%29), and it's well 
understood from a phenomenological standpoint, but not from a really basic 
physics standpoint. I find van de Hulst's treatment from 1953 (his "Light 
Scattering by Small Particles") to be a most approachable beginning to 
understand the phenomenon, and he suggests that surface waves on dielectrics 
were a promising explanation more than 50 years ago (and still are the best 
explanation, so far as I know). 


 /**************************************
"The four points of the compass be logic, knowledge, wisdom and the unknown. 
Some do bow in that final direction. Others advance upon it. To bow before the 
one is to lose sight of the three. I may submit to the unknown, but never to the 
unknowable." ~~Roger Zelazny, in "Lord of Light"
***************************************/




________________________________
From: "Quist, Oren" <Oren.Quist@SDSTATE.EDU>
To: Forum for Physics Educators <phys-l@carnot.physics.buffalo.edu>
Sent: Wed, February 23, 2011 10:22:35 AM
Subject: Re: [Phys-l] Interesting Shadows

Yes, I agree it is not Poisson's spot, but there is a halo around the shadow.

________________________________________
From: phys-l-bounces@carnot.physics.buffalo.edu 
[phys-l-bounces@carnot.physics.buffalo.edu] On Behalf Of John Denker 
[jsd@av8n.com]
Sent: Wednesday, February 23, 2011 11:04 AM
To: Forum for Physics Educators
Subject: Re: [Phys-l] Interesting Shadows

On 02/23/2011 09:29 AM, Quist, Oren wrote:
> In interesting shadow is seen when viewing the shadow on the ground
> of an airplane in the air when viewed from the planes.  I have seen
> this a couple of times from a commercial airliner at relatively high
> altitudes.  (Poisson's Spot ??).

Yes, it is interesting ... but no, it's not Poisson's spot.

Among the various interesting things you might see are flashes
coming from various cat's-eye reflectors.  There are lots of
retro-reflective things out there, including some traffic lane
markers, some road signs, bicycle safety reflectors, et cetera.
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