Coloured sectors

HOW

1. Look at the pattern on the stationary disc.
2. Rotate the disc at different speeds.
3. Pay attention to what you see when you blink.

WHY

As the disc rotates slowly, you can see blurred, coloured streaks at the edges of the yellow and blue sectors. It is believed that the explanation for this phenomenon is similar to that of Benham’s disk.

When the disk rotates rapidly, you will see a uniformly green surface. This colour is the result of the ‘compounding’ of yellow and blue. Sometimes yellow-blue flashes also appear. You will notice them while blinking. For that fraction of a second when you close your eyes, not enough colour signals reach the brain for the colour green to emerge.