The key to most color mixing is that pigments and color filters pass a broad
range of wavelengths of light, not just one wavelength of light. The brain
then takes this mix of wavelengths, averages the spectrum, and interprets it
as a single "color." This leads to a lot of confusion because most simple
explanations don't take the range of wavelengths into account. Mixing blue
and green averages out to cyan because the spectrum is enhanced in the
wavelength region where the two colors overlap. If you had a blue filter
with a very narrow wavelength bandpass, stacked on top of a green filter
with a very narrow bandpass, so that the two wavelength ranges didn't
overlap, then these filters would block the light entirely. But particles in
mixed pigments are more side-by-side than blocking each other, so the
reflected blue & green colors average.
Vickie Frohne
-----Original Message-----
From: Forum for Physics Educators
To: PHYS-L@lists.nau.edu
Sent: 5/19/2004 10:11 AM
Subject: Color Mixing (Pigment) question
Our physics book (h.s.) had a question about what color is obtained when
pure green and pure blue pigment are mixed. The book answer was "cyan
pigment." Can someone explain this please?
Why is the result not black? The blue pigment filters out red & green
light and the green pigment filters out blue & red light, so why isn't
the result black?
Thanks for your input.
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