Written by the Fiveable Content Team • Last updated September 2025
Verified for the 2026 exam
Verified for the 2026 exam•Written by the Fiveable Content Team • Last updated September 2025
Definition
A photon is a particle of light defined as a discrete bundle (or quantum) of electromagnetic (or light) energy. Photons are always in motion and, in vacuum, travel at a constant speed to all observers.
The range of all possible frequencies of electromagnetic radiation. It's like the menu from which the photon (the food item) comes from.
Quantum Mechanics: This is the branch of physics that deals with tiny particles like photons. It's like the rulebook for how our postman delivers his packets.
Energy Level: This refers to the quantized state of an atom where a photon can be absorbed or emitted. It's akin to different mailboxes where our postman can deliver his packets.