Unit Overview

Theme E: Nuclear and quantum physics

IB Physics HL· 5 min read 📊 17-19% of total exam score

1. Unit at a Glance

This unit progresses from foundational core concepts to advanced HL extension topics, moving from the structure of the atom to the fundamental particles that make up all matter. Core topics E.1–E.4 are required for all IB Physics HL students, while AHL topics E.5–E.7 add deeper coverage of quantum mechanics, nuclear energy, and particle physics.

Below is the full list of sub-topics in this unit, ordered sequentially for learning:

E.1 Energy levels and radioactivity

Introduces atomic energy levels, radioactive decay modes, and decay kinetics.

★★⏱ 10 min

E.2 Nuclear structure and reactions

Explores nuclear binding energy, mass defect, and conservation rules for nuclear reactions.

★★★⏱ 12 min

E.3 Quantum physics: photons and matter waves

Covers the photoelectric effect, wave-particle duality, and the de Broglie wavelength.

★★★⏱ 12 min

E.4 The nuclear atom

Covers Rutherford scattering, the discovery of the nucleus, and key nuclear properties.

★★⏱ 8 min

E.5 Quantum mechanics and the nucleus (AHL)

Explores quantum tunneling, the Heisenberg uncertainty principle, and nuclear models.

★★★★⏱ 15 min

E.6 Fission and fusion (AHL)

Analyzes energy release, chain reactions, and applications of fission and fusion.

★★★⏱ 14 min

E.7 The Standard Model of particle physics (AHL)

Describes fundamental particles, forces, and Feynman diagrams for particle interactions.

★★★★⏱ 16 min

2. Common Pitfalls

Wrong move:

Mixing up the definition of mass defect and its connection to binding energy

Why:

Students often reverse the mass difference calculation, leading to incorrect binding energy values

Correct move:

Mass defect $Δ m = \sum m_{nucleons} - m_{nucleus}$ , and binding energy $E_{b} = Δ m c^{2}$

Wrong move:

Treating wave-particle duality as a property that applies only to light or only to matter

Why:

Students often forget duality is a universal property of all quantum entities

Correct move:

All quantum particles (photons, electrons, protons) exhibit both wave and particle behavior, depending on the measurement

Wrong move:

Confusing which energy process (fission/fusion) releases energy for light vs heavy nuclei

Why:

Students misremember the trend of binding energy per nucleon vs mass number

Correct move:

Light nuclei release energy via fusion, heavy nuclei release energy via fission; both move toward iron, the most stable nucleus

3. Quick Reference Cheatsheet

Concept / Formula	Description
$E = Δ m c^{2}$	Mass-energy equivalence for binding energy and nuclear reactions
$N = N_{0} e^{- λ t}$	Radioactive decay law for remaining undecayed nuclei
$λ = \frac{l n 2}{t _{1/2}}$	Relationship between decay constant and half-life
$λ_{d B} = \frac{h}{p}$	de Broglie wavelength of a particle with momentum $p$
$E = h f = \frac{h c}{λ}$	Energy of a single photon
$h f = Φ + E_{k_{ma x}}$	Einstein's photoelectric effect equation
$Δ x Δ p \geq \frac{ℏ}{2}$	Heisenberg Uncertainty Principle (AHL)

What's Next

Begin your study of this unit with the first core sub-topic, E.1 Energy levels and radioactivity, to build foundational knowledge of subatomic energy behavior and radioactive decay. Work through each sub-topic in order, as core concepts build sequentially, before tackling the advanced AHL extension topics. After completing this unit, you will progress to the next IB Physics HL unit.