Re: ATM Focault Testing

[Ken Hunter <kb7h@cei.net>]

At 08:58 AM 12/29/98 -0800, you wrote:

>I guess the quantifying question is:  How do you intersect the reflected
>light from your light source without intersecting your view of the mirror so
>as to analyze the shadows?
>
>Any insight would be helpful.  (Sorry for such a basic question!).
>Bob Meeks
>
>
>

The thing that makes the Focault test work is that the light from the pin
hole has
some finite width. If it were one photon wide, then the mirror on the stand
would be
either dark or light (assuming perfect optics) as the light cone was
intercepted by the 
knife edge but, since the pin hole has width, some of the light is able to
"get around"
the knife edge and into your eye because it is coming from the mirror along
a different 
path... Also works this way for light coming from the mirror that has been
reflected 
from the varying slopes of figuring.

Ken Hunter