Exchange from Oskar
at IPP 13 , Breukelen 1993


Polariser Slides

Polariser Slides are made of linearly polarising materials put in slide
frames, both of which used to be abundantly available in photography shops
in the 1990's. Each slide has four polarisers in different orientations.
When two polarisers are put onto each other with 90-degrees angle between
their material orientation, then it becomes dark and one cannot see through.
The object of the puzzle is to place the Polariser Slides in the correct
order and orientation, such that all four sections become dark. Of all 192
possible combination, there is only one solution, albeit quite a few near
misses with three dark sections. It helps wearing polarising sunglasses to
solve this puzzle, as this makes it easier to identify the slides and their