physics trick

From: denis bider (
Date: Mon Jan 22 2001 - 07:22:57 MST

Hello everyone,

I'm not entirely sure whether this puzzle is on topic - it's probably more
so than the guns debate I triggered, but anyway - here it is:

Suppose we have two canvases, each 100m x 100m in size. We also have two
LARGE buckets of paint; we shall call these color1 and color2.

On the first canvas, we paint square tiles of alternating color, each square
being 0.25m x 0.25m in size. I.e., the first square has color1, the second
one has color2, then color1 again, and so on until we paint the whole
canvas. After we're done, the canvas should look like a chessboard:


On the second canvas, we paint a balanced mixture of color1 and color2:


Then we hang both canvases on something large and remove ourselves far
enough away not to see the individual square tiles on the first canvas. What
is the perceived color of the first canvas? What is the perceived color of
the second canvas? Are they the same?

- denis

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