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IPhO Modern Physics Problem Set (Official Problems + Hints)

Curated IPhO modern physics problems (relativity, quantum, particle/nuclear, astrophysics) with outlines and common traps.

  • International Physics Olympiad preparation

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Modern physics at IPhO is about constraints and scales: invariants, quantisation, and energy balance.

Before you start

If you have not done the hub path yet, start with the IPhO Modern Physics Hub.

Source PDFs

Archive mirror index: https://phoxiv.org/contests/ipho

Official documentations page: https://www.ipho-new.org/documentations/

Fading-hint route (recommended order)

  1. Read the framework once: IPhO Problem-Solving Framework

  2. Do the hub Entry and Core lessons first (then return here):

  3. Start with sections A and B below (starter problems).
  4. Finish the hub lessons, then do section C (core).
  5. Do section D (experimental) once per week.
Show the full hub lesson path (Modern Physics | IPhO Prep)
  1. Special Relativity Toolkit
  2. Quantum Tools (Order of Magnitude)
  3. Atomic Spectra: Models and Estimates
  4. Nuclear Decay and Binding Energy
  5. Relativistic Collisions and Invariants
  6. Quantum Wells and Tunneling Toolkit

A. Particle/Nuclear and High-Energy Modelling

  • IPhO 2016 T3 — “Large Hadron Collider” (PDF)
  • IPhO 2018 T2 — “Where is the neutrino?” (PDF)
Outline pattern: energy scales and invariants
  • write the conserved quantities first (energy, momentum, charge, lepton number if relevant) - identify the dominant scale (MeV vs GeV, eV vs keV) before calculation - sanity check with limiting cases: non-relativistic or ultra-relativistic regimes

B. Atomic/Quantum Control and Traps

  • IPhO 2024 T2 — “Trapping Ions and Cooling Atoms” (PDF)
Outline pattern: quantum/atomic problems without over-deriving
  • identify the relevant length and energy scales first - keep one clean approximation and label the small parameter that justifies it - check: does your result behave sensibly as the trap strength goes to zero?

C. Astrophysics-Style Modern Physics

  • IPhO 2024 T3 — “Black Widow Pulsar” (PDF)
  • IPhO 2023 T2 — “Neutron Stars” (PDF)
  • IPhO 2025 T1 — “Hydrogen and galaxies” (PDF)
Outline pattern: astrophysics with a short toolkit
  • start with conservation laws and scaling (do not chase exact constants too early) - treat the system as a one-zone model unless told otherwise - do 2 sanity checks: units and one extreme limit (very dense, very dilute, very large radius)

D. Experimental Modern Physics

  • IPhO 2020 E1 — “Crystallography” (PDF)
  • IPhO 2021 E2 — “LEDs” (PDF)
Write-up pattern: modern experiments
  • state the model and what line/plot gives the parameter - label axes with transformed quantities and units - show how uncertainty in slope becomes uncertainty in the physical constant - evaluation: name one dominant systematic and its direction of effect
Practice loop

Do one astro-style modelling problem and one experimental section per week. Then continue via the IPhO Modern Physics Hub.

Back to IPhO Problem Sets