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Re: [Phys-l] Projecting Black



I tried it, and as far as I can tell the blackness of the writing is less deep than the blackness the shadow of my hand in front of the board produces.
Skip

-----Original Message-----
From: phys-l-bounces@carnot.physics.buffalo.edu [mailto:phys-l-bounces@carnot.physics.buffalo.edu] On Behalf Of Ron Curtin
Sent: Tuesday, November 06, 2007 2:36 PM
To: 'Forum for Physics Educators'
Subject: [Phys-l] Projecting Black


A student asked me a question that I couldn't answer. When I pick up the
black pen on my Smart Board, I can write with a really black color --- much
blacker than the appearance of the screen with no illumination at all.
Where does the black come from? I can produce most all the other possible
colors with a combination of the primary colors of light, but if I add all
the colors of light together, it seems like I should get white, not black.
Any help?

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