Rainbow Factory

Why it matters

For two thousand years everyone knew prisms ADD colour to pure white light. Newton bought a second prism and ruined everyone's certainty.

The idea in plain words

The experiment that settled it. Tap the terms.

white = V+I+B+G+Y+O+R

Why does a diamond flash colours but a glass window doesn't?

Same physics, different geometry — sorting needs non-parallel faces

• the split: dispersion — splitting of white light into its colours — because μ varies with wavelength
• the order: VIBGYOR — violet deviates most, red least — the spectrum's fixed order
• Newton's clincher: recombination — an inverted second prism reassembles white — proof the prism adds nothing
• Diamond: huge dispersion + TIR bounces the colours apart before they exit
• Window: parallel faces recombine directions immediately

Predict first

Pass the rainbow from one prism through a SECOND, inverted prism. What comes out?

The second prism bends every colour back by the same amounts — out comes white. The colours were IN the white light all along; the prism only sorts, never creates.

• White light — the colours recombine — correct
• An even wider rainbow
• Darkness — the colours cancel

What you do

Split white light into VIBGYOR, then add the inverted prism and put the rainbow back together.

Check yourself

The colours of the spectrum differ in…

In vacuum all share c; it's wavelength that defines colour and drives dispersion in glass.

A pure single colour (say sodium yellow) through a prism…

Monochromatic light has one wavelength: one μ, one deviation, no spectrum.

Raindrops make rainbows by…

Sunlight enters, disperses, reflects inside, disperses more on exit — millions of drops, one arc.

• wavelength (and frequency) — violet shortest λ, red longest — correct
• speed in vacuum
• amplitude
• deviates but does NOT disperse — nothing to split — correct
• splits into VIBGYOR
• passes straight
• refraction + internal reflection + refraction — each drop is a tiny prism — correct
• reflecting the colours of the ground
• scattering like the blue sky