Rotating disk with black and white lines makes color illusion.

Rotating disk with black and white lines makes color illusion. Benham's Disk: The disk has one half of black, and the other half of white. On the white half, lines of concentric arcs are placed as shown. As the disk is rotated, colors seem to appear. For example: the outer circle may appear light tan, the two inner circles may appear green, and the innermost circle may appear blue. The colors vary with the speed of the disk, and the colors may be perceived differently from person to person. If the disk is stopped, then rotated in the opposite direction, the order of the colors reverses. The explanation is not fully known, but it may be that the rotating arcs cause low frequency stimulation of the color receptors in the retina of the eye. Note: Leybold Rotator pulleys are set for the highest speed