IGCSE 0625 / Section 3.2 / Core

Splitting white light.

Send a beam of white sunlight through a glass prism and it fans out into a band of colour, the same spread you see in a rainbow. The prism has not added anything; it has simply sorted the colours that were there all along.

The key idea

White light is a mixture of colours. A prism refracts each colour by a slightly different amount, so they separate into the spectrum: red, orange, yellow, green, blue, violet. Red is refracted the least and violet the most. This separation is dispersion.

Definition · learn the exact words

Dispersion is the splitting of white light into the colours of the spectrum by a prism, because each colour is refracted by a different amount.

red refracts least, violet refracts most

Monochromatic light is light of a single colour, that is a single frequency or wavelength. A prism refracts it at each face but does not disperse it, so it stays a single beam. The colours are already present in white light; the prism separates them.

Section 01

Fan out the spectrum.

Send white light into the prism and watch it split into its colours, with red bent least and violet most.

Stage 1 · Learn

Check dispersion

Four quick checks. Each correct answer earns XP and lights this skill on your star map.

Quick check+10 XP

Splitting white light into colours using a prism is called...

Quick check+10 XP

White light is...

Quick check+10 XP

A prism separates the colours because each colour...

Quick check+10 XP

Which colour is refracted (bent) the most by a prism?

Section 02

Sorted, not created.

The prism separates colours that white light already contains, bending each by a different amount.

Examiner trap

Red light is refracted the least and violet the most, a pair that is easy to reverse. And the prism does not create the colours: they are already present in white light, and the prism simply separates them.

Stage 2 · Exam

Exam-style questions

Unlocks once the four checks above are done. Worth more XP, written in the style of Paper 2.

Finish the four checks above to unlock the exam questions
Exam style+20 XP

When white light passes through a prism, the colour bent the least is...

Exam style+20 XP

A prism produces a spectrum because different colours of light...

Exam style+20 XP

The correct order of the spectrum from least to most refracted is...

Skill unlocked

Dispersion, mastered.

That completes the light strand. The electromagnetic spectrum is next.

-Rank -Level -Score -Topics
Go deeper · practice
Six original Cambridge-style questions
Dispersion of white light by a prism, why colours separate, and the order of the spectrum from least to most refracted. Attempt each, then reveal the worked solution.
Stage 3 · master the unit
Waves challenge
Mixed questions across the whole unit, each one worth XP. Start this only when you feel confident across every topic in the unit, not just dispersion.
Start the unit challenge →