Le 30/12/2009 14:30, somebody nous fit lire :
> There are two light sources, pure red and green, practically coincident and
> pointing in the same direction. You place a filter that's a perfect yellow
> blocker in the path. What colour light would you see past the filter?

My answer: I would perceive yellow.
If I was a prism, I would get a red and a green ray.

Hypothesis: red source is a spectral ray in red
green source is a spectral ray in green
yellow blocker is a spectral blocker in the yellow lightwave, as it is
perfect, it does not stop rays in red or green spectrum.
So both rays go through.

Then my imperfect eyes get excited by the red & green rays, (triggering
the red & green spectral-large cones), information get transmitted to
the brain which has no way to separate that flux from an actual yellow
light, so will interpret it along the simplest way: it's a yellow light.

Of course, I assumed you ask me as a average human. If I was a bee or a
dog (on internet, how could you know), or colour-blind, my answer would
be different.

Last point, you did not talk about the intensity of each light sources...

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