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Re: an optical illusion?



The red/blue contrast does suggest chromatic aberration but for me it is
definitely related to wearing my glasses. However, I tried 3 pairs--one old
(and expensive)blended bifocals, my current pair, and a pair of single
prescription reading glasses and I see the effect with all--maybe my eyes
aren't very aberrant but the glasses are. The question still remains why
the brain would trigger one eye to preferentially view the blue and the
other the red (I'm assuming this is the case since covering one eye makes
the illusion disappear.) I suppose this could be related to however those
3-D pictures that you have to stare at cross-eyed work, but then I don't
understand that either.

Rick

----- Original Message -----
From: "N. Pete Lohstreter" <petel@TENET.EDU>
To: <PHYS-L@lists.nau.edu>
Sent: Sunday, July 02, 2000 7:53 PM
Subject: Re: an optical illusion?


I was under the impression that the effect has to do with the differing
index of refraction of waves of differing wavelength by the eye. The
blue is focused closer to the lens and requires a slight focus change to
see it clearly. The brain interprets this as a change in distance to
the object being viewed. I supposed this is the same as chromatic
aberration mentioned in another reply.

Rick Tarara wrote:

Help me out in understanding this one:

Riding home from a wedding today I was looking at the list of songs on
the
Santana 'Supernatural' CD. The titles are written in many different
colors.
What struck me was that they appeared VERY 3-D, with reddish letters
standing out and blue being pushed into the background--except that one
title (The Calling--if you have the CD) had the red letters on dark
background stand out while the red letters on blue background were
pushed
back.

OK, my 'experimental observations'. The number one feature was that I
only
observe the 3D behavior when looking through my glasses (blended
bifocals)
but I can hold the case away and look with the distance part or closer
and
use the reading part and maintain the 3-D look. The phenomenon does
require
both eyes (not surprising) but does not require the plastic case of the
CD.
It seems to require pretty good illumination, but both sunlight and
fluorescent light work.

Anybody want to explain? My main concern is whether the phenomenon
somehow
is related to a 'fault' in my glasses. Can anyone with this CD and
glasses
see the same behavior.

Rick

**************************************************
Richard W. Tarara
Associate Professor of Physics
Department of Chemistry & Physics
Saint Mary's College
Notre Dame, IN 46556
219-284-4664
rtarara@saintmarys.edu

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--
Pete Lohstreter "Reality is merely an illusion,
The Hockaday School albeit a very persistent one."
Dallas, TX 75229 A. Einstein
petel@tenet.edu
plohstreter@mail.hockaday.org
http://www.hockaday.org