Newton's Colour Disc
A spinning disc painted with rainbow segments blurs into white — proof that white light is a mix of colours.
Start building ↓The build
Divide the disc
Split a card circle into seven equal rainbow segments.
Colour them
Fill each segment with a spectrum colour.
Mount to spin
Fix it to a motor shaft or string spinner.
Spin fast
At high speed the colours blend toward white-grey.
When the disc spins too fast for the eye to separate the colours, your brain averages them together, recombining the spectrum into white.
A closer look
It demonstrates additive colour mixing and persistence of vision — the same effect Newton used to argue white light contains all colours.
Variables to test
- 1 Try only red-green-blue segments — still whitish?
- 2 Spin slower; at what speed do colours reappear?
More Physics
Homopolar Motor
A single AA battery, a magnet and a copper-wire loop spin into the simplest electric motor that actually works.
Switchable Electromagnet
Coil insulated wire around an iron bolt and a battery turns it into a magnet you can switch on, off, and strengthen at will.
Pendulum Timer
A swinging mass keeps remarkably steady time — build one and discover what really sets its rhythm.