Bob Ammerman wrote: > > > > > My understanding of the process is that the tape is made to appear black > by > > making its thickness an odd number of half wavelengths thick in the > visible > > light region, but this then is not an odd number of half wavelengths thick > > at the infra red region. It maybe that this applies to the die molecules > in > > the tape rather than the tape itself. > > This doesn't make sense, because you can stretch electrical tape to at least > twice its original length (thus thinning it significantly) without seeing > any strange optical effects. > > Besides: > > 1: It would require high precision control of the thickness > > 2: What about red, green, blue, yellow, white, etc. electrical tapes? > > Bob Ammerman I'm suspicious too. For many years I have always used black PVC electrical tape on VCRs specifically as a quick convenient cover for infra-red sensors, on literally thousands of occasions, and never seen evidence of IR getting through the tape. This is standard practice in the VCR reapir industry. I do buy a decent quality tape though.?? -Roman -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.