1What "color" is really made of
White light is a mix — and surfaces are picky bouncers
You only need two ideas. Watch each one:
White light is every color stirred together
Plain white light is secretly a mix. Red, green and blue light are all riding along inside it at once. Split it with a prism and the rainbow falls out.
A surface bounces some colors, soaks up the rest
Nothing makes its own color. A surface soaks up some colors and bounces the leftover ones to your eye. The color you see is just the color it bounces.
2Two ways a surface can act
The honest mirror vs the picky apple
Shine the very same light at two surfaces and they follow opposite rules:
The honest mirror
Sends back every color it's given — so it just shows you whatever color the lamp is.
The picky apple
Soaks up almost everything and bounces back only red — so it can show red and nothing else.
3Your turn — change the lamp's color
Slide the lamp through the rainbow and watch the apple
Drag the slider to mix the lamp's color. Watch what bounces off the picky apple: red rays only ever fly off it when there's red inside the lamp. When the red runs out, the apple has nothing to send back.
4Now add a green leaf beside the apple
Same green lamp, two things at once. Who survives? 💡
The apple goes black under green light — we know that now. So here's the real test: put a green leaf right next to it and flip on that same green lamp. Guess first, then tap the lamp and watch both.
Guess before you flip the switch
Under that pure green light, the red apple fades to black. Right beside it sits a green leaf. The lamp's color matches the leaf — so what happens to the leaf?