Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!umich!wsu-cs!egrunix!besler
From: besler@egrunix.UUCP (Brent Besler)
Newsgroups: sci.electronics
Subject: Re: Bad News- Lasers replace Radar guns
Keywords: radar laser police
Message-ID: <366@egrunix.UUCP>
Date: 19 Jan 90 18:40:19 GMT
References: <7263@lindy.Stanford.EDU> <13398@cit-vax.Caltech.Edu> <354@egrunix.UUCP> <7334@lindy.Stanford.EDU>
Reply-To: besler@unix.secs.oakland.edu.UUCP (Brent Besler)
Distribution: na
Organization: Oakland University, Rochester, MI
Lines: 16

In article <7334@lindy.Stanford.EDU> sorka@ucscb.UCSC.EDU (Alan Waterman) writes:
>
>Are you sure the light intensity with vary 1/(distance^4)
>That makes sense if the source emmits in a sphere, reflects and comes\
>back as a sphere. But the laser shoots in a strait line so almost
>all the light from the source reaches the destination. Am I wrong about
>the laser beam?

I am a chemistry type, not an optics expert, but I think it goes as follows:
The intensity of any em radiation beam goes down as 1/(distance**2).  THe
laser beam on the speed measuring device is about 4 ft. wide at 1000 ft.
Only a small portion of the beam will be reflected back at the car.  The 
relfection from the car behaves as if it were another light source(in a model
treatment anyway).

						    Brent H. Besler