Colour illusions: Mach band effect

The rings which appear when the disc is spinning are perfectly uniform, yet they appear to be fluted. This is a result of what is known as the 'Mach Band Effect'. This occurs when two circles of uniform brightness are placed side by side, separated by a sharp edge. Just along the edge one colour looks darker than it really is, while the other looks lighter. In the spinning disc this creates the illusion of bands appearing to be fluted.