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IPhO Waves & Optics Problem Set (Official Problems + Hints)

Curated IPhO waves/optics problems grouped by technique (wave models, interference, polarization), with outlines and common traps.

  • International Physics Olympiad preparation

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On this page

Waves/optics problems are won by choosing a representation and tracking phase cleanly. This set trains that habit.

Before you start

If you have not done the hub path yet, start with the IPhO Waves & Optics 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 sections C and D (core).
  5. Do sections E and F (stretch) after you are comfortable.
Show the full hub lesson path (Waves & Optics | IPhO Prep)
  1. Phasors & Superposition
  2. Wave Equation & Boundary Conditions
  3. Standing Waves, Resonance & Q
  4. Interference & Diffraction Estimates
  5. Polarization & Jones Vectors
  6. Ray Optics: Paraxial Tricks & ABCD Matrices

A. Big-Picture Wave Modelling (Signals and Boundaries)

  • IPhO 2018 T1 — “LIGO-GW150914” (PDF)
Outline pattern: wave modelling at olympiad speed
  • identify the wave variable and the governing equation in the bulk - enforce boundary conditions explicitly (fixed/free, impedance, reflection phase) - estimate a characteristic frequency/wavelength before detailed work

B. EM Waves and Resonators

  • IPhO 2019 T2 — “Microwave Oven” (PDF)
Outline pattern: cavity and resonance thinking
  • write what sets the mode scale (dimension gives k or lambda) - track energy flow and losses to connect to Q or heating rates - do a consistency check: if losses go to zero, Q should grow

C. Laser/Optics Systems (Tools and Estimation)

  • IPhO 2020 T3 — “Laser Technologies” (PDF)
  • IPhO 2022 T2 — “James Webb Space Telescope” (PDF)
Outline pattern: optics systems without drowning in algebra
  • start with ray/geometry for scales, then refine with wave corrections - identify which quantity is being optimized or bounded (resolution, throughput, stability) - keep one small-angle/paraxial approximation and justify it

D. Diffraction, Interference, and Phase

  • IPhO 2024 E2 — “Diffraction from Phase Steps” (PDF)
  • IPhO 2019 E1 — “Optical Measurements” (PDF)
Write-up pattern: diffraction experiments
  • sketch the geometry and define the phase difference clearly - identify what sets the fringe spacing or angular scale first - use plots that make a straight line, and interpret slope with units

E. Polarization and Anisotropy

  • IPhO 2023 E2 — “Birefringence” (PDF)
Outline pattern: polarization with Jones-style bookkeeping
  • choose a basis (fast/slow axes, or horizontal/vertical) and stick to it - treat elements as transformations (matrix or component-wise rules) - sanity check with special cases: analyzer parallel/perpendicular, quarter-wave vs half-wave

F. A Mixed Modern-Wave Problem (Read the Model Carefully)

  • IPhO 2021 T3 — “Particles and Waves” (PDF)
Outline pattern: mixed-topic wave problems
  • identify which wave model is intended (classical wave vs quantum wave) - write the scale first (de Broglie wavelength, coherence length, bandwidth) - test the limiting regimes (long wavelength vs short wavelength)
Practice loop

Pair one optics experiment section with one theory wave model problem each week. Then continue via the IPhO Waves & Optics Hub.

Back to IPhO Problem Sets