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Re: [Phys-L] Polaroid Filter Question



I'd agree with circular polarization. See also modern 3d theatre glasses.
Dan m

Sent from my iPad

On Apr 1, 2015, at 22:18, brian whatcott <betwys1@sbcglobal.net> wrote:

A plausible explanation, (easily tested!)

If a filter provides an oriented polarization ONLY, then two such filters will provide a similar angular dependency for transmission when placed in either order. If one such filter also provides line to circular polarization, then its placement second in line will allow the usual extinction of transmitted light.
If however, it is placed first, the extinction with rotation property is lost.

Brian Whatcott

On 3/31/2015 10:06 PM, Michael Barr wrote:
Hi, I only have a few polaroid filters. I couple from old cameras, a few
from IMAX 3D movies, and then some plastic ones that came with science ed
kits. When two filters are placed at 90 degree to each other almost all
light is blocked out, but with some the the filters it only works when lets
say filter 1 is first and 2 is second. Reverse the filters and keep the
angles the same and light goes through at all angles. This does not happen
with my camera filters but does happen with the plastic filters I have.
Based on the way I teach (and learned) polaroid filters, the order should
not matter, just that they are perpendicular. Anyone have a clue what is
going on?
Thanks,
Mike Barr

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