# Nuclear and quantum physics

> IB Physics SL · IB SL Physics
> Source: https://www.owlsprep.com/study/ib-physics-sl-u5-overview/
> Weight: 19-21% of total exam

This unit explores atomic structure, radioactive decay, core quantum phenomena, and nuclear energy reactions, forming the foundation of modern physics for IB Physics SL.

**Prerequisites:** [Mechanics: energy and momentum](https://www.owlsprep.com/study/ib-physics-sl-u2-overview/); [Basic wave properties](https://www.owlsprep.com/study/ib-physics-sl-u4-overview/)

## Learning objectives

- Describe the core structure of atoms, nuclei, and fundamental nuclear particles
- Apply decay laws and conservation rules to solve problems involving radioactivity and nuclear reactions
- Explain key quantum phenomena including the photoelectric effect and wave-particle duality
- Compare nuclear fission and fusion, calculate their energy output, and describe their practical applications

## 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](https://www.owlsprep.com/study/ib-physics-sl-u5-atomic-structure/) — Covers nuclear composition, isotopes, and Rutherford scattering that revealed the modern atomic model.
- [Radioactive decay](https://www.owlsprep.com/study/ib-physics-sl-u5-radioactive-decay/) — Explains types of decay, decay constants, half-life calculations, and activity for radioactive samples.
- [Nuclear reactions](https://www.owlsprep.com/study/ib-physics-sl-u5-nuclear-reactions/) — Covers mass defect, binding energy, and conservation laws for balancing nuclear reaction equations.
- [Quantum physics](https://www.owlsprep.com/study/ib-physics-sl-u5-quantum-physics/) — Introduces the photoelectric effect, photon properties, wave-particle duality, and the de Broglie hypothesis.
- [Nuclear fission and fusion](https://www.owlsprep.com/study/ib-physics-sl-u5-nuclear-fission-and-fusion/) — Compares fission and fusion processes, energy release, and their use for commercial power generation.

## Common pitfalls

- **Wrong:** Confusing mass defect with binding energy
  - Why it fails: Mass defect is a mass difference, while binding energy is the energy equivalent of that difference
  - Correct: Use $E = \Delta m c^2$ to convert mass defect to binding energy
- **Wrong:** Treating photons as only wave or only particle
  - Why it fails: Wave-particle duality means all quantum objects have both properties simultaneously
  - Correct: Accept that both properties are observed depending on the experiment design
- **Wrong:** Predicting decay timing for an individual nucleus
  - Why it fails: Radioactive decay is a random process; we can only calculate probabilities for large populations
  - Correct: Use half-life and decay laws to predict total activity for large samples

## Cheatsheet

| Concept | Key Formula |
| --- | --- |
| Photon energy | $E = hf = \frac{hc}{\lambda}$ |
| Decay constant & half-life | $\lambda = \frac{ln 2}{T_{1/2}}$ |
| Radioactive activity | $A = A_0 e^{-\lambda t}$ |
| Mass-energy equivalence | $E = \Delta m c^2$ |
| de Broglie wavelength | $\lambda = \frac{h}{p}$ |
| Photoelectric effect | $E_{kmax} = hf - \phi$ |
| Binding energy per nucleon | $\frac{BE}{A} = \frac{\Delta m c^2}{A}$ |

## 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.

- [Atomic structure (first sub-topic of this unit)](https://www.owlsprep.com/study/ib-physics-sl-u5-atomic-structure/)
- [Radioactive decay](https://www.owlsprep.com/study/ib-physics-sl-u5-radioactive-decay/)
- [Nuclear reactions](https://www.owlsprep.com/study/ib-physics-sl-u5-nuclear-reactions/)

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