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Re: [OM] Detecting polarizer type?

Subject: Re: [OM] Detecting polarizer type?
From: Roger Wesson <roger@xxxxxxxxxxxxxxxxxxxxxxx>
Date: Thu, 07 Mar 2002 10:40:01 +0000
I have a slightly simpler method of distinguishing between linear and
circular polarisers:

Equipment: Polariser, blue sky

Method: Look through filter at blue sky, rotate filter.  Turn filter
over, Look through at blue sky, rotate filter

Results: If the sky darkens and lightens the same way both sides, it's
linear.  If the sky darkens and brightens one way but not the other,
it's circular.

Roger
(Physics postgrad but still can't really understand why this happens)

"John A. Lind" wrote:
> 
> At 01:00 3/7/02, Daniel J. Mitchell wondered:
> >  Is there any way to distinguish a linear from a circular polariser?
> 
> Yes!
> Equipment required:
>    a.  Mirror
>    b.  Polarizer
>    c.  One eyeball (and *only* one eyeball; see procedure)
> Procedure:
>    a.  Look in mirror at your own reflection and close one eye.
>    b.  Hold polarizer in front of the *open* eye.
>    c.  Observe whether you can see your open eye behind the polarizer
>          in your reflection.
>    d.  Turn polarizer over and look through it again.
>          (Keep the other eye closed!)
>    e.  Observe whether you can see your open eye behind the polarizer
>          in your reflection.
> 
> Evaluating Test Data:
>    a.  If you can see your open eyeball looking through the polarizer
>          in both directions, it's a linear polarizer.
>    b.  If you can see your open eyeball looking through the polarizer
>          one direction, but not the other (because the polarizer is
>          pure black), it's a circular polarizer.
>

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