> > I once saw an electron micrograph of a CDRom, it was covered with > > indentations tens of microns wide by 100's of microns long, so I guess its > > acting something like a diffraction gating combined with a diffuse > > reflector. > > Has anyone actually had any success using a CD Rom as a signalling mirror > > over realistic distances? > >This would be useful for the paddlers and campers in > my office as a number of us have towers many feet high of discarded > disks). > I wonder if the diffraction grating surface has something to do with > this? Perhaps a physicist in the group could reflect on this. > Mike Probably the diffraction effect had much to do with the colors Peter Osman mentioned. We've also tried them out around here in NJ. They could be spotted from hilltop to hilltop; if so, then probably by an airplane as well. Two keys to make them work: One is that you don't want a steady light -- a flash is much more of an attention getter. The other is that you have to be relatively sure that that flash of light is aimed where you want it. That's why signal mirrors have a hole in them. I've found it helpful to stick my hand out in front and line up my fingertips with the target. Then illuminate my fingers with the light as I sight through the hole while holding the CDRom at my face. Then wiggle it a little..... Joe P. *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************Received on Sun May 27 2001 - 19:58:32 PDT
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