Physics · Optics
Light & Optics
Bend real light rays with lenses, mirrors and prisms.
Also on your phone · Optics Light Lab
The course
6 worlds · 53 lessons
World 1 · Reflection & Refraction
FREEHow light travels, bounces, and bends- 01Light Travels in Straight LinesRays, beams, and shadows · 6 min
- 02The Law of ReflectionAngle in equals angle out · 7 min
- 03Plane Mirrors & ImagesVirtual images and left–right flips · 6 min
- 04Bouncing Around CornersPeriscopes and multi-mirror paths · 7 min
- 05Refractive IndexLight slows down in matter · 7 min
- 06Snell's LawThe exact refraction equation · 9 min
- 07Toward or Away from the NormalWhich way does light bend? · 6 min
- 08Apparent DepthWhy pools look shallower · 6 min
- 09Refraction You See Every DayStraws, coins, and mirages · 5 min
- 10World 1 ReviewReflection and refraction, together · 8 min
World 2 · Lenses & Mirrors
PROFocusing light and forming images- 01Converging & Diverging LensesTwo shapes, two behaviours · 7 minPRO
- 02Focal Length & PowerHow strongly a lens bends light · 6 minPRO
- 03The Thin-Lens Equation1/f = 1/dₒ + 1/dᵢ · 9 minPRO
- 04MagnificationBigger, smaller, upright, inverted · 7 minPRO
- 05Diverging LensesAlways upright, always smaller · 6 minPRO
- 06Concave MirrorsMirrors that focus · 7 minPRO
- 07Convex MirrorsA wider field of view · 6 minPRO
- 08The Eye as a LensFocusing on your retina · 7 minPRO
- 09The CameraAperture, focus, and the sensor · 6 minPRO
- 10World 2 ReviewDesign a two-lens relay · 8 minPRO
World 3 · Dispersion & Colour
PROSplitting white light into a spectrum- 01White Light Is Many ColoursThe visible spectrum · 6 minPRO
- 02DispersionIndex depends on wavelength · 8 minPRO
- 03Inside the PrismTwo refractions, one spectrum · 8 minPRO
- 04How Rainbows FormRaindrops as tiny prisms · 7 minPRO
- 05Material MattersWhy diamond sparkles · 6 minPRO
- 06Adding Colours of LightRed + green + blue · 6 minPRO
- 07Why Objects Have ColourAbsorption and reflection · 6 minPRO
- 08World 3 ReviewFrom beam to spectrum · 8 minPRO
World 4 · Exam & Deep Optics
PROCritical angle, fibre optics, instruments- 01The Critical AngleWhen refraction runs out · 8 minPRO
- 02Total Internal ReflectionA perfect mirror made of glass · 8 minPRO
- 03Fibre OpticsTrapping light in a thread of glass · 7 minPRO
- 04Prisms in InstrumentsBinoculars and reflectors · 6 minPRO
- 05The Refracting TelescopeObjective plus eyepiece · 8 minPRO
- 06The Compound MicroscopeTwo lenses, huge magnification · 7 minPRO
- 07The Reflecting TelescopeMirrors instead of lenses · 7 minPRO
- 08AberrationsWhy perfect focus is hard · 6 minPRO
- 09Exam WorkshopAP/physics-style problems · 9 minPRO
- 10World 4 ReviewThe full optical toolkit · 8 minPRO
- 11Eye ClinicAxial length, dioptres, and a prescription · 8 minPRO
- 12Young's Double SlitLight as a wave: two slits, one interference pattern · 7 minPRO
- 13Diffraction GratingsThousands of slits sharpen the pattern into orders · 6 minPRO
- 14Thin-Film ColoursWhy a soap bubble is never just one colour · 6 minPRO
- 15Polarisation & Malus's LawLight waves that only wiggle one way · 6 minPRO
- 16Everyday PolarisersSunglasses, LCD screens and camera filters · 5 minPRO
- 17Ray vs Wave: Choosing the Right ModelTwo engines, two different jobs · 5 minPRO
World 5 · Wave Interference
PROTwo sources, the double slit and standing waves in a ripple tank
World 6 · Eye & Ear
PROFocusing light on the retina, sorting sound along the cochleaRead first
All guides →Guides for Light & Optics
ParentsSun, Earth & MoonScience at Home With the Family Plan: A Weekly RoutineHow a family can use the Family plan: kid profiles, a weekly rhythm, safe kitchen-table follow-ups and good questions to ask, from a short weekly parent e-mail.
ExplainerLight & OpticsReflection and Refraction Explained: Mirrors and Snell’s LawHow light bounces off mirrors and bends into water or glass: the law of reflection, refractive index, Snell’s law and why pools look shallow. With a live lab.
ExplainerSun, Earth & MoonWhy Day Length and Shadows Change: Earth, Sun and ShadowsHow a spinning Earth gives day and night, why daylight hours depend on where you stand, and how Sun height sets shadow length so a stick can tell the time.