Radar alert

[quk@sievers.com (Phil Payne)]

In message <961018224728_546452918@emout01.mail.aol.com> STEADIRIC@aol.com writes:

> >A friend of mine living in Germany tells me that down there speed cameras 
> >are with flashes. So people hand CDs on their rear-view mirrors and the 
> >highly reflective surface of a CD blinds the cameras using their own flash.
> 
> VERY DOUBTFUL........  A cd is in effect a mirror, a mirror reflects 
> light according to the following "Angle of incendences equals the angle 
> of reflection" Meaning that if the flash comes from +30 deg's it reflects 
> at -30 deg's....  Besides it's too far from the plate and too small to do 
> anything....

It _does_ sound like an urban myth.

However, a CD is not just a mirror - it's also a circular diffraction grating.  
I suspect it might have some quite interesting properties in the infrared 
spectrum.  

--
 Phil Payne
 phil@sievers.com
 Committee Member, UK Audi [ur-]quattro Owners Club