Helps you understandanother area
EclipsesAn eclipse is a shadow, and shadows need light that travels in straight lines.
Light
What is light, how does it travel, and why can you see this page at all?
Light travels in straight lines at extraordinary speed, bounces, bends, splits into colours and lets you see. Find out how, and why shadows, mirrors and rainbows behave as they do.
5 depths≈ 201 min of reading80 practice questions
The ladder
Choose how deep to go
Every depth is open. Start where it feels interesting — you can always move back.
- Discoverabout 30 minLight: how you can see anything at allMeet light as the messenger that carries the world to your eyes: what makes its own light and what only reflects it, why light travels dead straight, how that one fact explains shadows, and first looks at mirrors, bending and the colours inside white light.Owner-accepted · not line-by-line reviewed
- Understandabout 40 minHow light behaves: rays, angles and rules you can useTurn the facts of Discover into rules that predict. Work out shadow sizes with similar triangles, meet umbra and penumbra, apply the law of reflection to mirrors and periscopes, see why light bends when its speed changes, and separate the two opposite kinds of colour mixing.Owner-accepted · not line-by-line reviewed
- Investigateabout 42 minChasing light: measuring, mirroring and bending it on purposeStep into the shoes of Rømer and Fizeau to measure something that seemed instant, then turn detective on curved mirrors, lenses pushed to a magnifier, total internal reflection in a diamond and a fibre-optic cable, and finally the exact geometry that puts a rainbow at 42 degrees from the Sun.Owner-accepted · not line-by-line reviewed
- Go deeperabout 45 minPrecise light: derivations, corrective lenses and the shape of a rainbowFollow the speed of light to its modern exact definition, derive the mirror/lens formula from similar triangles, work out lens powers for short and long sight, put numbers on fibre-optic latency, and see why the rainbow's angle is a genuine minimum.Owner-accepted · not line-by-line reviewed
- Extendabout 44 minWaves, particles and the light you cannot seeStep past visible light into the wider spectrum, meet the wave-versus-particle debate (light is genuinely both), measure light's speed with a microwave and a chocolate bar, see how bending stretches every day, and use light-years to look into the past.Owner-accepted · not line-by-line reviewed
Practise and apply
Question bank · 80 questions
9 sections from Foundation to Challenge, each with hints and a worked solution — or play a 10-question round for points and stars.
Foundation 19Core 27Stretch 19Challenge 15
The web
Connected ideas
Follow a connection when you’re curious — some lead into completely different areas.
Light
Helps you understandanother area
Phases of the MoonThe Moon has no light of its own: we see the half of it the Sun is lighting.
Used inanother area
Anatomy of the human bodyThe eye is a lens, a screen and a shutter — optics built out of living tissue.
Contrasts with
SoundBoth travel as waves and carry energy, but light needs no material and races a million times faster than sound.
Related to
ElectricityA bulb, an LED and a solar panel are all conversions between electricity and light.
Words to know
53 words are explained in these lessons
LightLuminousNon-luminousRayBeamTransparentTranslucentOpaqueShadowScreenReflectionImage+41 more