Topic Cluster

Nuclear Physics

Nuclear physics: inside the atomic nucleus — radioactivity, half-life, binding energy, and the fission and fusion reactions that power stars and reactors.

Nuclear Physics — the core equations of nuclear physics, and every article on the topic
The equations this topic keeps coming back to.

What Is Nuclear Physics?

Nuclear Physics is the study of the nucleus: what holds it together, how it comes apart, and how much energy that releases. It is where a milligram of matter turns into the output of a power station.

Core equations in nuclear physics
RelationshipEquationWhat it tells you
Radioactive decayN = N0 · (1/2)^(t / t½)How many nuclei are left after time t
Half-lifet½ = ln2 / λTime for half the sample to decay
ActivityA = λ · NDecays per second
Decay energyQ = Δm · c²Energy released by a mass defect
Binding energyE = Δm · c²Energy holding the nucleus together
AttenuationI = I0 · e^(−μ·x)Gamma intensity through shielding
Radioactive Decay Chains: What Happens After the First Decay
Nuclear Physics

Radioactive Decay Chains: What Happens After the First Decay

A radioactive decay chain is what happens when the daughter of a decay is radioactive too: its activity climbs from zero, peaks at the exact instant it equals the parent's, and then falls in step with the parent that feeds it. Three regimes cover every case - secular, transient and no equilibrium at all - and which one you get depends only on the two half-lives. Eight worked problems on three real chains, three original diagrams, an interactive lab and a calculator.

18 min read