Science
What is a photon?
A photon is a single particle of light — the smallest possible packet of electromagnetic energy. Light behaves both as a wave and as a stream of these particles, and photons carry energy that depends on the light's color (frequency).
See it, don’t just read it.
Watch a 2-minute lesson with voice + animation that explains a photon.
Key things to understand
- 1It's the fundamental particle of light and all electromagnetic radiation.
- 2It has no mass and always travels at the speed of light.
- 3Its energy depends on frequency — blue photons carry more than red.
- 4Light acts as both a wave and a stream of photons.
- 5Photons power vision, photosynthesis, and solar panels.
Frequently asked questions
- What is a photon?
- The smallest unit of light — a massless packet of electromagnetic energy that always moves at the speed of light.
- Is light a wave or a particle?
- Both — light shows wave-like and particle-like behavior depending on how it's measured, a cornerstone of quantum physics.
- Do photons have mass?
- No — photons are massless, which is why they can travel at the speed of light.