IB Physics Extended Essay: The Complete Guide

By Michael Thompson · Education Specialist; 10 years teaching the IB at Bromsgrove School · Published 4 September 2026 · Updated 6 October 2026

The IB physics extended essay is a 4,000-word independent research paper that forms part of the compulsory DP core - and one of the few places in the IB where you define the question yourself. That freedom is also the trap: vague questions, weak data handling, and descriptive rather than analytical writing account for most of the marks lost in physics submissions. This guide walks through the assessment criteria, how to build a viable research question, what experimental work actually requires, and where physics essays consistently fall short - so you can avoid the same mistakes.

Key Takeaways

In This Article

  1. What the IB Physics Extended Essay Actually Is
  2. Assessment Criteria and Marks Explained
  3. What Makes a Good Physics EE Research Question
  4. Experimental Physics EEs: Data, Uncertainties, and Theoretical Models
  5. Where Physics EEs Lose Marks Most Often
  6. Word Count, Formatting Rules, and the RPF
  7. Physics EE Topic Ideas Worth Exploring
  8. What to Do Next

1. What the IB Physics Extended Essay Actually Is

The IB Physics Extended Essay is a mandatory, externally assessed component of the IB Diploma Programme core, alongside Theory of Knowledge (TOK) and CAS. It takes the form of an independent 4,000-word research paper, written on a question of your own choosing, assessed by an external IB examiner.

The central requirement is specific: the essay must answer a focused research question using physics principles. According to the IB's subject guidance, evidence can come from personal experimentation or secondary sources, but whichever route you take, you must apply the principles of physics rather than simply describe findings. A well-sourced literature review that never reasons physically will not score well.

One non-obvious point about audience: write for a reader who already knows the DP physics course. That means you can cite Newton's laws without proving them, but anything outside the standard DP syllabus must be explained and referenced. Students often waste words explaining basic mechanics while leaving genuinely advanced content unexplained.

The EE grade (A to E) combines with your TOK grade in a matrix to award 0 to 3 bonus diploma points. An E grade in either the EE or TOK is a failing condition for the diploma, regardless of your subject scores.

2. Assessment Criteria and Marks Explained

The IB overhauled the Extended Essay assessment model in February 2025, with first assessment under the new framework in May 2027. The new model has five criteria totalling 30 marks, applied to every essay whatever the subject. Criteria A to D are applied to the essay as a whole; Criterion E is applied only to your reflective statement.

The new five-criterion model (30 marks)

CriterionMarksWhat it looks for in a physics EE
Framework for the essay6A focused, answerable research question, a method matched to it, and a structure that supports communication
Knowledge and understanding6Accurate physics concepts, appropriate theory, and well-chosen sources
Analysis and line of argument6Data interpretation, uncertainty handling, and a coherent argument structure
Discussion and evaluation8Conclusions tested against theory, honest treatment of limitations
Reflection4A reflective statement of up to 500 words on the RPF showing evaluation and growth, not a diary

Discussion and evaluation carries the most weight at 8 marks, which surprises many students who focus almost entirely on data collection. A technically strong experiment with a thin evaluative section will not score well here.

The Reflection criterion is assessed only from your reflective statement on the Reflection and progress form (RPF), not the essay itself. The IB's update guidance describes it as evaluating the EE's effect on you as a learner, with emphasis on transferable skills.

Older sample essays and the legacy model

> November 2026 candidates only: your session is the last on the old 34-mark model: Focus and method (6), Knowledge and understanding (6), Critical thinking (12), Presentation (4) and Engagement (6), with Engagement assessed from the Reflections on planning and progress form (RPPF), three reflections totalling up to 500 words.

The IB's published physics sample essays were marked under that old model, so treat their scores as a guide to quality, not as marks on the 30-mark scale. Physics Example B (eddy currents and damping coefficient) is a mid-range essay where sourcing and layout both lost marks. Physics Example C (draining a cylindrical tank) is a stronger essay held back from the top band by minor inconsistencies in its argument. Both were published with the pre-2027 guide, so ask your supervisor whether they can share them as calibration tools.

3. What Makes a Good Physics EE Research Question

The research question is the single most important sentence in your IB physics extended essay. Get it wrong and every subsequent section suffers, because the IB requires the essay to apply the principles of physics and go beyond merely informing the reader. A vague or mis-categorised question makes both of those demands almost impossible to meet.

Category-appropriate means physics, not adjacent to physics

A question belongs in physics when its answer depends on a physical principle or mathematical relationship. Questions that sit in engineering optimisation, pure mathematics, or subjects where physics is incidental (chemistry, biology) will not earn full marks under the IB EE assessment criteria, even if they sound scientific.

The engineering mis-categorisation trap (written for this guide): "What is the optimal fin shape for a model rocket?" That is a design question. It asks for a best configuration, not a physical relationship. An examiner will note the absence of a testable physical principle and mark the research question strand of Criterion A accordingly.

What a strong question actually looks like

A good physics EE research question is specific, measurable, and names the variable being changed and the physical law or model being tested. Compare these examples (written for this guide):

LabelQuestionWhy
WeakHow does temperature affect a material?No physical model named; no measurable output specified; far too broad for 4,000 words
StrongerHow does the length of a freely oscillating pendulum affect the period, and how closely does the measured relationship match the small-angle approximation?Names the variable, the output, and the theoretical model
StrongWhat is the relationship between the diameter of a circular aperture and the radius of the central diffraction maximum, and how does this compare to the Rayleigh criterion?Links a measurable geometric variable to a named optical principle with a quantitative benchmark

The non-obvious distinction between "stronger" and "strong" is the benchmark. A question that invites comparison against a theoretical prediction forces you to engage with the physics deeply, which directly satisfies the IB's requirement for personal and original thinking. A question that only asks "how does X affect Y" can be answered with a graph and a trend line.

The school-resource constraint

Before finalising any physics extended essay research question, check whether you can actually collect the data your question demands. A question about gravitational wave frequency is category-appropriate but unanswerable with school equipment. The IB guidance permits evidence drawn from personal experimentation or book- and internet-based research, so a literature-based question is valid, but it still needs to be answerable within 4,000 words with sources a school student can access and fully explain.

Draft your question, then ask: can I name the independent variable, the measured output, and the physical principle being tested? If any of those three is missing, rewrite before your supervisor approves the topic.

4. Experimental Physics EEs: Data, Uncertainties, and Theoretical Models

An experimental IB physics extended essay works when three conditions hold: you can collect enough data points to identify a clear trend, you have consistent access to the equipment throughout the investigation, and you have a theoretical model to test your results against. Remove the third condition and you are left with description, not analysis.

Uncertainty propagation is not optional. Random uncertainties in your raw measurements must be identified, propagated through every calculation, and then discussed in relation to your conclusions. If your final result has an uncertainty range wide enough to swallow the deviation from theory, that is not a failure to hide; it is your most important finding. Examiners expect you to say so explicitly.

The IB's assessed sample essays, marked under the pre-2027 criteria, illustrate the difference between partial and strong execution. Physics Example B, on eddy currents and damping coefficient, had a clear research question, but the data analysis was only partially effective, and the examiner noted that the discussion was only partially connected to the research question. By contrast, Physics Example C, which investigated the time required to drain a cylindrical tank, aligned theory and experiment from the outset and scored noticeably higher.

A well-structured experimental section follows this order:

The non-obvious pitfall is collecting data first and looking for a theory afterwards. Raw numbers without a model to test are a descriptive account. Build the theoretical prediction before you run a single trial, so your data collection is structured around testing specific variables in the model.

5. Where Physics EEs Lose Marks Most Often

In the IB's published example on eddy currents and damping, marked under the pre-2027 criteria, the examiner noted that the "application of sources" was only partially effective and that some layout considerations were missing or applied incorrectly. These are not unusual weaknesses. The same failure modes appear across physics EEs repeatedly.

Data problems are the most common route to losing marks under the analysis criterion:

Source problems are subtler. Citing a physics education website instead of a peer-reviewed source is one issue. The less obvious one is failing to explain theory that sits beyond the Diploma Programme curriculum. If your EE uses concepts from university-level electromagnetism, you need to derive or clearly explain them, not assume the examiner will fill the gap.

Scope problems cut both ways. A question covering three sub-variables at once produces three shallow treatments. A question so narrow that it can be answered in two paragraphs leaves nothing to analyse.

Description instead of analysis is the single most penalised pattern. Narrating what you did, or summarising the theory you read, is not the same as interpreting what your results mean in relation to your research question.

Layout and labelling errors weaken the structure strand of Criterion A (Framework for the essay), which in the sciences expects clearly labelled tables, diagrams and graphs. Common ones include:

Each of these is a straightforward fix before submission.

6. Word Count, Formatting Rules, and the RPF

The IB's hard ceiling is 4,000 words, and examiners stop reading at that point. Words above the limit are ignored, so a conclusion buried past 4,000 words simply does not exist for marking purposes.

What the word count includes and excludes:

Examiners are not required to read appendices, footnotes or endnotes, so anything your argument depends on belongs in the body.

Mandatory presentation elements:

The less-obvious gotcha: a graph without a caption or axis units is an incomplete figure. The 2027 sciences guidance expects data tables, diagrams and graphs that can be clearly understood and are appropriately labelled, and structure is assessed under the Framework criterion, which carries 6 of the 30 available marks.

The RPF: the Reflection and progress form records your attendance at three mandatory reflection sessions with your supervisor, the last of which is the viva voce, a short interview after the essay is finished. At the end of the process you write one reflective statement on the RPF of no more than 500 words. It is submitted with the essay and read by the examiner. The Reflection criterion is worth 4 marks and is assessed solely on that statement, not the essay body. A purely descriptive statement ("I met with my supervisor and discussed my progress") scores at the lower descriptors regardless of essay quality. The statement should evaluate how the EE changed your thinking and skills, with specific examples, not just record that meetings happened.

7. Physics EE Topic Ideas Worth Exploring

The IB's EE guidance for the sciences is clear that the topic must have a strong focus on the subject it is submitted in, so a physics EE must apply the principles of physics, not merely touch on a physics-adjacent theme. That distinction matters more than students usually expect when picking a topic.

The four things a viable topic needs: personal interest, measurable variables, a clear theoretical model, and accessible equipment. All four. A topic with three out of four tends to collapse at the experimental design stage or the analysis stage.

Topic areas that sit squarely in physics, with example directions:

AreaExample research direction
AcousticsMeasuring the speed of sound in different media (air, water, wood) and comparing results to the elastic modulus model
OpticsInvestigating how the focal length of a converging lens changes with temperature
ElectromagnetismAnalysing the relationship between current and magnetic field strength inside a solenoid against the Biot-Savart prediction
Thermal physicsPlotting the cooling curve of a copper cylinder and testing Newton's law of cooling across a range of temperature differentials
Mechanics and oscillationsExamining how the damping coefficient of a pendulum varies with the viscosity of the surrounding fluid
Nuclear/radioactive decayUsing a Geiger-Muller tube to model decay constants and compare experimental half-life to published values
Fluid dynamicsInvestigating how the drag force on a sphere scales with velocity in a viscous fluid

One non-obvious gotcha: topics framed around optimisation ("design the most efficient...") almost always drift into engineering and lose the theoretical physics thread the examiner is looking for. Similarly, topics that are essentially pure mathematics ("prove the Fourier transform of...") do not satisfy the requirement to apply physics principles to evidence. Keep the research question anchored to a physical relationship you can measure and model.

8. What to Do Next

First, confirm which EE model applies to you. The new EE framework launched in February 2025, with first assessment in May 2027: if you sit your exams in May 2027 or later, the 30-mark criteria in this guide apply, and November 2026 is the last session marked under the old criteria. If you are unsure, ask your IB coordinator this week.

Then read the sciences section of the IB's Extended essay guide (first assessment 2027), which your supervisor or coordinator can share with you. It explains how each criterion applies to science essays and includes example physics research questions.

Before your first supervisor meeting, draft two or three candidate research questions. Supervisors give sharper feedback when the conversation is about narrowing and refining rather than generating ideas from nothing. Read that section today, and bring written questions to your first meeting rather than waiting to be prompted.

FAQ

How long is the IB extended essay?

The IB extended essay has a 4,000-word maximum; the count covers the introduction, main body, conclusion and quotations, and excludes tables, graphs, equations, citations and the bibliography.

What is the extended essay in the IB?

The extended essay is a mandatory, externally assessed piece of independent research in the IB Diploma Programme core, resulting in a formal academic paper of up to 4,000 words on a question the student chooses within a DP subject.

Will the IB physics extended essay be hard?

Difficulty depends largely on question scope: a narrowly focused, experimentally testable question with a clear theoretical model is manageable, while an overly broad or poorly defined question makes the analysis section almost impossible to execute well.

What are the IB extended essay assessment criteria from May 2027?

The current guide, published in February 2025 and first assessed in May 2027, has five criteria totalling 30 marks: Framework for the essay (6), Knowledge and understanding (6), Analysis and line of argument (6), Discussion and evaluation (8), and Reflection (4).

What physics topics are suitable for an IB extended essay?

Good physics EE topics sit within recognised physics domains - mechanics, optics, electromagnetism, thermal physics, acoustics, or nuclear physics - and involve a measurable variable, a theoretical model to test against, and equipment accessible to a school student.

How is reflection assessed in the IB extended essay?

From May 2027, Criterion E (Reflection, 4 marks) is assessed only from one reflective statement of no more than 500 words on the Reflection and progress form (RPF), written after the viva voce, so a generic or purely descriptive statement directly costs marks.

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