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Red Eye, Reprise



Hi Physics Phriends !

Thanks for the many responses to my Red Eye query (5 Physhare, 2 private.
Sorry if I seemed a little impatient. There's a reason.

So far all responses have given essentially the same reason:

Joe Zawicki explained:

My understanding is that the red eyes seen in photographs are due to the
light reflecting off of the capillary bed of the retina.

Matt Tuley responded:

The red eye effect is caused by light from the flash reflecting off of the
back of the eye, which is indeed red.

NOW HERE IS WHY I ASKED: I have a domino mosaic picture of Einstein on the
wall up at the front of the room illuminated with fluorescent lights. A
student took a flash photograph using a simple camera with outdoor color
film in it.

When I asked the other science teachers here at Deerfield what causes Red
Eye, they gave the same "reflect off the red retina" answer. When I handed
them the photograph of the Einstein mosaic, they break out laughing.

You can guess why. The domino Einstein has Red Eye (and nose bridge). The
camera was aimed directly at the eyes. Had it been aimed at the moutasche,
I'm sure it would have reflected red.

I await your explanation of why the black dominoes which relected the flash
directly back to the film appeared red. Is it the combination of a little
bit of white light from the dots plus the "black light :-) " from the black
paint added up to red? I seem to remember seeing a demo of a rotating
black and white disc create the sensation of red in my eyes. What is going
on here?

Why my impatience? I plan to pass this picture around at the joint meeting
of CAPO (Chicago Area Physics Organizations) next Wednesday (1/15) at
Elmhurst College and I would like your input before I go. If you live in
the Chicago area, you might like to attend. It is the annual joint meeting
of the four physics teacher sharing groups and we always have a good time.
Phood and Phellowship at about 5:30 p.m. and sharing at 7:00 p.m. The
Elmhurst College physics building is at the SE corner of the campus.

My formal 10 minute sharing will be to use the Voyager II astronomy program
to show the Hale-Bopp comet from above the solar system (x = 12.5 au, y =
0, z = 21.6 au) from 10/1/96 to 5/30/97. Then to show it from Deerfield,
IL for a 3 month period (Mar, Apr, May) at 8:00 p.m. and a 3 month period
(Jan. Feb. Mar.) at 5:00 a.m. If time permits, I'll show the retrograde
motion of Mars which occurs next spring both from above the solar system
and from the earth using the same software.

If you know why Einstein has Red Eye, please respond.

Thanks, DiRT

P.S. If you would like the mapping of the domino Einstein mosaic, please
send me a stamped, self-addressed envelope and I'll be happy to send it to
you. You only need 4 boxes of dominoes

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David R. Thiessen FUN + PHYSICS = PHUN
Science Department PHYSICS IS PHUN !!
Deerfield High School
1959 North Waukegan Road Education increases your freedom
Deerfield, IL 60015 Because It Increases Your Options !!
Home phone (815) 337-2883
School phone (708) 405-8488 Education will enrich your life
Voice Mail (708) 374-3811 then *610 Even if it doesn't enhance your income !!
School Fax (708) 945-0970
Remember when students brought teachers
Apples instead of driving them bananas ??

dthiessn@nslsilus.org (Quote sources long forgotten)
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