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How does Newton's color disk work?

Newton's disk - Take a circular white color disk, make 7 equal intersections and paint section with respective VIBGYOR colors, now when you spin the disk in certain speed, it appears white.

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Could you five some more information on what that is? – Mark Eichenlaub Apr 14 '11 at 6:20
Newton's disk - we take a circular white color disk make 7 equal intersections and Paint section with respective VIBGYOR colors,Now when you spin the disk in certain speed,It appears white. – Green Horn Apr 14 '11 at 6:32
up vote 4 down vote accepted

The perception of a picture or a color stays in the human brain for a fraction of a second. Newton's color disk is a mechanical device that rotates an array of colors arranged as petals or gradients around an axis and when the disc rotates fast enough the perception of the color changes to white. This is because white light is nothing but the mixture of light of all wavelengths in the visible range.

Sir Isaac Newton used this device to prove the above assertion that white color is the mixture of all colors.

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@sb1 small matter, but I thought it was the photoreceptor cells on the retina that retain the sensation of color, not really the brain itself. (Then again I'm not a biologist) – David Z Apr 14 '11 at 6:54
if the receptors in the eye have some relaxation time similar to a CCD then it doesnt matter if the colours don't arrive simultaneously as long they arrive within some finite dt, then the signals can be either mixed in the eye sending white to the brain or the signals will overlap when arriving at the brain and again the result is white (or grey!). But I also am not a biologist. – Nic Apr 14 '11 at 10:02
@Georg: not only problem of "perfect paints". If the disk is painted 3 primary colors (RGB), each kind of photoreceptor registers given primary color 1/3 the time, lack of said color 2/3 the time. Meaning the brightness of the "white" is reduced by 2/3 vs brightness of the 3 paints just mixed together. Use CMY instead for only 1/3 reduction of brightness (each primary color is present on 2 out of 3 fields.) – SF. Apr 14 '11 at 11:05
There's an even more interesting optical illusion that is sort of "dual" to Newton's disk. If you take a disk with a black and white pattern on it, and rotate it, it appears to have color (for certain combinations of rotation speed and spacing between black and white regions). I don't know what this one is called, unfortunately. I think that the explanation is that the white excites all three color receptors in the eye, but the three receptors have different decay times, so that a time-varying black-and-white signal will end up exciting some receptors more than others, in a time-average sense. – Ted Bunn Apr 14 '11 at 14:13
@Ted It's called "I actually got sick just thinking about a black and white spining disk. :-(" – corsiKa Apr 15 '11 at 5:28

protected by Qmechanic Mar 15 '13 at 15:33

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