The front cover of this issue of Physics Education (http://www.iop.org/EJ/journal/PhysEd) has a picture that explains just this. You don't see colour using the standard RGB three cones model. Your brain takes into account the colours surrounding objects that you look at. The cover pic has a cube on it with what appears to be an orange square and a brown square. They are in fact the same colour. The first time I saw this illusion I skipped over it as what the blurb said seemed obviously untrue, there was no way they were the same...
Cheers
Gary
G. D. Williams, Editor, Physics Education National Coordinator, IoP Teacher Networkgary.williams@iop.org gdwilliams100@hotmail.com> From: ron.curtin@charlottecountryday.org> To: phys-l@carnot.physics.buffalo.edu> Date: Tue, 6 Nov 2007 15:35:38 -0500> 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?> > _______________________________________________> Forum for Physics Educators> Phys-l@carnot.physics.buffalo.edu> https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l
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