Science
What is Light?
Light is a form of energy that travels as electromagnetic waves and lets us see the world. It moves at about 300,000 kilometres per second — the fastest anything can travel — and behaves as both a wave and a stream of particles called photons.
See it, don’t just read it.
Watch a 2-minute lesson with voice + animation that explains light.
Key things to understand
- 1Light is electromagnetic radiation; visible light is the small part of the spectrum our eyes can detect.
- 2It travels at roughly 300,000 km/s in a vacuum — the universe's speed limit.
- 3Light acts as both a wave (with wavelength and frequency) and particles called photons — known as wave–particle duality.
- 4Different wavelengths appear as different colours; white light is a mix of all of them, as a prism reveals.
- 5Beyond visible light, the spectrum includes radio waves, microwaves, infrared, ultraviolet, X-rays, and gamma rays.
Frequently asked questions
- Is light a wave or a particle?
- Both. Light shows wave behaviour (like bending and interference) and particle behaviour (photons carrying energy) — a famous idea called wave–particle duality.
- How fast does light travel?
- About 299,792 kilometres per second in a vacuum — nothing with mass can reach this speed, which is why it's called the cosmic speed limit.
- Why does light have colour?
- Colour comes from wavelength. Shorter wavelengths look blue or violet, longer ones look red, and a mix of all visible wavelengths looks white.