Re: [Phys-L] just for fun

[brian whatcott <betwys1@sbcglobal.net>]

On 12/18/2013 2:18 PM, Christopher M Gould wrote:
> 	From: Phys-l [mailto:phys-l-bounces@phys-l.org] On Behalf Of John Denker
> 	Sent: Wednesday, December 18, 2013 11:11 AM
> 	To: Phys-L@Phys-L.org
> 	Subject: [Phys-L] just for fun
> 	>  You start out in the attic.  There are three switches.  It is known that there are three light bulbs in the basement.  The switches control the lights, but you don't know which goes with which.  You get to make *one* trip to the basement to figure this out.  How?
>
> Just for fun.  Assuming that there is a one-to-one correspondence between switches and lights, assuming that all lights work, and assuming that you know which way is "on" for all three switches, then one solution is to turn two lights on for a few minutes, then turn one off, and quickly run downstairs to see which light is dark but warm.
This is indeed the classic answer, which thermally codes the 
(incandescent) lamps.
I also liked the minimally invasive lamp load coding of one switch, with 
the second on and the third off. Other solutions need remote sensing of 
the basement with a wireless video cam, or a PC and web cam,  a camera 
on video record at the basement end, or  an accomplice or device at the 
attic end to signal a different flash sequence for each switch. One 
could also string a fiber guide from each light source back to the switch...

Brian Whatcott   Altus OK