Unit Overview

Nuclear and quantum physics

IB Physics SL· 5 min read 📊 19-21% of total exam

1. Unit at a Glance

We progress from the smallest building blocks of matter to large-scale energy applications, building concepts incrementally. First you will master atomic and nuclear structure, then study spontaneous radioactive decay, before moving to induced nuclear reactions. Next we cover core quantum concepts that define modern physics, ending with a detailed look at fission and fusion for energy production.

Work through the following sub-topics in order:

Atomic structure

Covers nuclear composition, isotopes, and Rutherford scattering that revealed the modern atomic model.

★★⏱ 8 min

Radioactive decay

Explains types of decay, decay constants, half-life calculations, and activity for radioactive samples.

★★★⏱ 10 min

Nuclear reactions

Covers mass defect, binding energy, and conservation laws for balancing nuclear reaction equations.

★★★⏱ 9 min

Quantum physics

Introduces the photoelectric effect, photon properties, wave-particle duality, and the de Broglie hypothesis.

★★★★⏱ 12 min

Nuclear fission and fusion

Compares fission and fusion processes, energy release, and their use for commercial power generation.

★★★⏱ 10 min

2. Common Pitfalls

Wrong move:

Confusing mass defect with binding energy

Why:

Mass defect is a mass difference, while binding energy is the energy equivalent of that difference

Correct move:

Use $E = Δ m c^{2}$ to convert mass defect to binding energy

Wrong move:

Treating photons as only wave or only particle

Why:

Wave-particle duality means all quantum objects have both properties simultaneously

Correct move:

Accept that both properties are observed depending on the experiment design

Wrong move:

Predicting decay timing for an individual nucleus

Why:

Radioactive decay is a random process; we can only calculate probabilities for large populations

Correct move:

Use half-life and decay laws to predict total activity for large samples

3. Quick Reference Cheatsheet

Concept	Key Formula
Photon energy	$E = h f = \frac{h c}{λ}$
Decay constant & half-life	$λ = \frac{l n 2}{T _{1/2}}$
Radioactive activity	$A = A_{0} e^{- λ t}$
Mass-energy equivalence	$E = Δ m c^{2}$
de Broglie wavelength	$λ = \frac{h}{p}$
Photoelectric effect	$E_{k ma x} = h f - ϕ$
Binding energy per nucleon	$\frac{B E}{A} = \frac{Δ m c ^{2}}{A}$

What's Next

Start with the first sub-topic of this unit, Atomic Structure, to build the foundational knowledge of nuclear composition that all subsequent nuclear and quantum concepts rely on. Work through each sub-topic in order, as earlier concepts are required to understand later topics like nuclear energy and quantum behavior. Once you complete this unit, move on to the next unit in the IB Physics SL syllabus.