Nuclear Physics
The science of atomic nuclei, radioactivity, and the strongest force in the universe.
🔵 Nuclear Structure
Atomic nuclei are composed of protons and neutrons (nucleons) held together by the strong nuclear force - the strongest of the four fundamental forces, acting at distances less than ~1 femtometer (10⁻¹⁵ m).
☢️ Radioactive Decay
Unstable nuclei spontaneously emit radiation: Alpha (α) - helium nucleus; Beta (β) - electron/positron; Gamma (γ) - high-energy photon. Half-life (t½) is the time for half the atoms to decay.
💥 Nuclear Fission
A heavy nucleus (e.g., U-235) splits into lighter nuclei when struck by a neutron, releasing enormous energy plus more neutrons. This chain reaction powers nuclear reactors and weapons. E = Δmc²
⭐ Nuclear Fusion
Light nuclei (e.g., deuterium + tritium) combine to form a heavier nucleus, releasing even more energy per unit mass than fission. Powers the Sun. ITER and NIF are the leading fusion research projects.
🔗 Binding Energy
The energy required to completely separate a nucleus into its individual nucleons. Iron-56 has the highest binding energy per nucleon - making it the most stable nucleus. Energy is released when nuclei move toward iron-56.
🌡️ Chain Reaction
Each fission releases neutrons that can trigger further fissions. A controlled chain reaction (reactor) maintains k=1. An uncontrolled reaction (bomb) has k>1. Critical mass is the minimum mass to sustain a chain reaction.
🧲 Nuclear Forces
The strong force binds quarks into nucleons and nucleons into nuclei. The weak force governs beta decay and is responsible for nuclear transmutation. Both are short-range forces.
🔬 Isotopes
Atoms of the same element with different neutron numbers. U-235 (0.7% natural abundance) is fissile; U-238 (99.3%) is not. Enrichment increases the U-235 fraction for reactor or weapon use.