Overview of the basic concepts and principles of nuclear physics, including the structure of the atomic nucleus, types of nuclear reactions, and the fundamental forces involved.
Introduction to Nuclear Physics – Study Notes
| Term | Meaning / Typical Value |
|---|---|
| Nucleus | Central core of an atom containing protons (Z) and neutrons (N). Radius ≈ 1–10 fm (1 fm = 10⁻¹⁵ m). |
| Atomic number (Z) | Number of protons; defines the element. |
| Mass number (A) | Total nucleons, A = Z + N. |
| Isotope | Nuclides with same Z but different N (e.g., ¹²C, ¹³C). |
| Binding Energy (BE) | Energy required to separate a nucleus into its constituent nucleons. |
| Binding Energy per Nucleon | BE/A; peaks near iron‑56 (~8.8 MeV), indicating most stable nuclei. |
| Radioactivity | Spontaneous emission of particles or photons from an unstable nucleus. |
| Half‑life (T½) | Time for half of a sample of radionuclides to decay. |
| Cross‑section (σ) | Effective area that quantifies the probability of a specific nuclear reaction (units: barn, 1 b = 10⁻²⁸ m²). |
| Force | Characteristics |
|---|---|
| Strong Nuclear Force | - Attractive at distances ≈ 1 fm. - Mediated by gluons (quarks) and, at the nucleon level, by mesons (pions). - Short‑range; vanishes beyond ~2–3 fm. |
| Electromagnetic Force | - Repulsive between protons (Coulomb repulsion). - Long‑range; counteracts the strong force, especially in heavy nuclei. |
| Weak Interaction | - Responsible for beta decay (n → p + e⁻ + ν̄ₑ, etc.). - Changes quark flavor, altering proton ↔ neutron. |
| Gravity | Negligible at nuclear scales (≈10⁻³⁶ times weaker than the strong force). |
Valley of Stability
Decay Modes