Quantum Physics — The Rules of the Very Small

Quantum physics describes nature at atomic and sub-atomic scales. At that level, particles behave as waves, outcomes are probabilistic, and properties that seem classical (like position and momentum) cannot both be known precisely at the same time.

Core Ideas

• Wave–particle duality — electrons, photons and atoms exhibit both wave-like and particle-like behaviour.
• Superposition — a quantum system can exist in a combination of states until it is measured.
• Entanglement — two particles can share a joint state in which measuring one instantly constrains the other.
• Heisenberg uncertainty — Δx · Δp ≥ ℏ/2.

Why It Matters

Quantum mechanics underpins lasers, semiconductors, MRI machines, solar cells and quantum computers. Every modern electronic device you own obeys quantum rules.

See also: Particle Physics, Physics Guide.