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Re: [OM] Identifying a filter and how to use it

Subject: Re: [OM] Identifying a filter and how to use it
From: sschaff@xxxxxxxxxxxxxxxxx
Date: Thu, 16 Apr 1998 11:00:13 -0700 (PDT)
? Kennedy wrote:

> The circular polariser is really two specialist filters sandwiched into
> one.  The first part is a normal linear polariser, and this works as you
> expect on the light that passes through it.  The V on the filter shows
> the orientation of the polarisation.  The second part of the sandwich is
> a special filter called a quarter wave plate.  This splits the polarised
> light from the first part into two parts and rotates one of them by
> 90deg, like an X.  

Just being pedantic, but I think a more precise description would be:
the quarter-wave plate splits the light into two components, each at
45 degress to the original polarization axis.  One component is
rotated in phase by 90 degrees (i.e. is retarded by one-quarter
wavelength) with respect to the other, which gives light in which the
polarization axis rotates -- i.e. circularly polarized light.

Steve Schaffner
sschaff@xxxxxxxxxxxxxxxxx


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