Physics

QCAA Physics IA3 Research Investigation Guide: Aim for 20/20

A current QCE Physics IA3 guide to claim analysis, research questions, secondary evidence, scientific arguments, evidence quality and claim evaluation.

By Sylligence · Published 2026-07-17 · Updated 2026-07-17 · 10 min read

A top-band Physics IA3 breaks the claim into scientifically testable parts, derives a measurable research question, compares sufficient evidence across sources, explains the relationships using physics, and then qualifies how far the findings can be extrapolated back to the claim.

There is no fixed number of studies, graphs or evidence sections that guarantees 20/20. Evidence is sufficient when it supports every material part of the research question deeply enough to construct and evaluate a scientific argument.

Physics IA3 at a glance

Under the Physics 2025 v1.3 syllabus, IA3 is a 20-mark Research investigation based on Unit 4: Revolutions in modern physics.

| Requirement | Current QCAA condition | | --- | --- | | Weighting | 20% | | Conditions | Approximately 10 hours of class time; individual response | | Response length | Written: up to 2000 words | | Evidence type | Secondary evidence from scientifically credible sources | | Forming and Finding | 5 marks | | Analysing | 5 marks | | Interpreting | 5 marks | | Evaluating | 5 marks |

The current sample instrument locates the task in special relativity, quantum theory and the Standard Model. Your school's claim may differ, but it must be relevant to Unit 4 subject matter.

What does the Physics IA3 ISMG reward?

The criteria describe four connected stages:

1. Forming and Finding: clearly develop a specific research question from the claim, select sufficient relevant sources, and use scientific genre and referencing conventions appropriately.
2. Analysing: identify sufficient relevant evidence, thoroughly identify its trends, patterns or relationships, and identify limitations of the evidence.
3. Interpreting: use the analysed relationships to justify scientific arguments and a conclusion to the research question.
4. Evaluating: justify the quality of evidence, extrapolate credible findings to the original claim, and propose considered improvements and extensions relevant to that claim.

This means an IA3 is not a sequence of source summaries. Each source should contribute evidence to a shared line of reasoning.

How do you break a Physics claim into a research question?

Claims often contain ambiguous or exaggerated language. Before writing the question, identify:

• the physical concepts assumed by the claim
• the quantities that could be measured or compared
• the system, particle, material or context being discussed
• the conditions under which the claimed relationship is expected
• which part of the claim can be answered within 2000 words and available evidence

For example, a claim about something travelling “faster than light” is scientifically ambiguous. It may confuse the invariant speed of light in vacuum with the lower phase velocity of light in a medium. Resolving that distinction is not avoiding the claim; it is necessary before deriving a valid Physics question.

A strong rationale makes the development visible:

claim → constituent concepts → ambiguity or testable relationship → measurable variables → scoped research question

Avoid choosing variables only because one graph is easy to find. The question should remain logically connected to the claim and to Unit 4 physics.

What makes a Physics IA3 research question specific and relevant?

The 2025 Physics subject report emphasises measurable independent and dependent variables. “Does quantum theory have practical uses?” is too broad. A more answerable question specifies the technology or phenomenon, a measurable input or condition, and an outcome that published evidence can compare.

Before committing to the question, check that:

• every important term is defined in the rationale
• the proposed variables appear in accessible evidence
• the evidence spans the range or conditions needed for the question
• the question can support a Physics relationship rather than a descriptive list
• answering the question will allow a qualified evaluation of the original claim

Search for evidence while refining the question. A theoretically elegant question is not workable if the available studies measure different quantities that cannot be meaningfully compared.

How should you plan complementary evidence strands?

Map each part of the question to the evidence it needs. One study may establish how an outcome changes with momentum, while another establishes how a threshold changes with refractive index. These strands can be sufficient when their synthesis answers the whole question.

| Evidence-planning question | What to record | | --- | --- | | What relationship does this source test? | Variables, conditions, range and relevant physical model | | Which part of my RQ does it answer? | The exact inference the evidence can support | | What must be compared across sources? | Units, definitions, particle/material type, model assumptions and measurement method | | What can this evidence not establish? | Range, resolution, noise, model or scope limitation |

Do not force studies with incompatible variables into one numerical comparison. They may still support different parts of the argument, but the connection must be explained explicitly.

How do you analyse evidence instead of summarising sources?

Begin important paragraphs with the relationship the evidence establishes, then use values, uncertainty or model features to support it. A useful reasoning sequence is:

trend or relationship → relevant Physics explanation → implication for the research question

For example, if a measured angle increases with particle momentum before approaching an asymptote, identify the range over which the change is strongest, explain the governing threshold relationship, and state what this reveals about detectability or the research question. Simply writing “Figure 1 shows an increase” does not construct a scientific argument.

When comparing sources, check whether apparent disagreement comes from:

• different particle species or masses
• different media or refractive indices
• different energy or momentum ranges
• experimental data versus theoretical simulation
• different definitions or measurement resolutions

The explanation should come from Physics, not from assuming that the newer or more prestigious source must be correct.

What is the difference between an evidence limitation and source credibility?

These are connected but distinct judgments.

• Evidence limitation: a property of the data or method that restricts the inference, such as a narrow momentum range, noisy measurements, an idealised model or conditions different from the research question.
• Source quality: whether the publication and the evidence it carries are credible, relevant, accurate, sufficiently current and affected by material bias.

“This source is peer reviewed” does not explain whether its data answer your question. “The graph has a narrow range” does not verify that the graph was produced transparently or accurately.

The 2025 subject report specifically recommends checking credibility, bias, relevance, accuracy and recency across multiple sources. Discuss the consequence: does the issue weaken confidence, narrow the conclusion, prevent comparison or leave one part of the question unresolved? See evidence limitations versus source credibility in QCE Science for a fuller comparison.

How do you construct a justified scientific argument?

A justified argument connects several levels of reasoning:

1. Identify what the evidence establishes.
2. Explain the relationship through the relevant Physics model or principle.
3. Reconcile supporting, complementary or conflicting evidence.
4. Account for limitations that affect the inference.
5. State the resulting answer to that part of the research question.

Physics terminology and equations should clarify the reasoning. An equation earns no value merely by appearing in the rationale; use it to explain why a threshold, curve, gradient, asymptote or difference between systems occurs.

The final RQ conclusion should synthesise the strongest relationships and the material limitations. It should also briefly retain the scientific reasoning that makes the answer defensible, rather than giving only a yes/no verdict.

How are the research-question conclusion and claim evaluation different?

The conclusion answers the narrow research question. The evaluation then asks how far that answer can be applied to the broader claim.

Suppose the evidence establishes a relationship for charged particles in one transparent medium over a limited momentum range. The conclusion can answer that scoped question. It cannot automatically prove a universal claim about every particle, every medium or light speed in vacuum.

A strong extrapolation states:

• which part of the claim is supported, challenged or clarified
• which credible findings justify that judgment
• which parts of the claim were not tested
• the conditions under which the judgment remains valid

This controlled extrapolation is stronger than declaring the whole claim “true” or “false”.

How should improvements and extensions be logically derived?

An improvement should respond directly to a limitation discussed in the evidence. If two studies use incompatible momentum ranges, an improvement might seek a dataset covering a shared range under comparable conditions. If the only evidence uses an idealised simulation, an improvement might add suitable experimental measurements to test the model under the same variables.

An extension investigates a new but claim-relevant scope. It might compare another particle species, medium, energy regime or application that the current question deliberately excluded.

Avoid “use more reliable sources” or “research more variables”. Name the missing evidence, explain what inference it currently prevents and specify how the new evidence would strengthen or extend the claim evaluation.

What a confirmed full-mark Physics IA3 teaches us

Sylligence reviewed a privately supplied Physics IA3 response that the student confirmed received full marks. Its wording, figures and task-specific results are not reproduced, and no teacher-annotated ISMG was supplied.

The response investigated a claim involving faster-than-light behaviour by first separating light speed in vacuum from phase velocity in a medium. It then used complementary evidence about particle momentum, refractive index, emission angle and threshold behaviour. The argument explained particle and mass effects, recognised range and noise limitations, and extrapolated only the supported findings back to the claim.

The transferable lesson is not that every Physics IA3 needs Cherenkov radiation, two studies or an asymptotic model. It is that claim clarification, evidence selection, physical explanation, limitation analysis and extrapolation should form one traceable argument.

Physics IA3 submission checklist

Forming and Finding

• Is the development from claim to research question explicit?
• Are the independent and dependent variables measurable and relevant to Unit 4?
• Do the sources collectively cover every material part of the question?
• Are citations and the reference list consistent?

Analysing

• Does each graph, table or result have a defined role in answering the question?
• Are trends described with specific evidence rather than broad summaries?
• Are cross-source differences in variables, scope and conditions accounted for?
• Does every important limitation explain its consequence for the inference?

Interpreting

• Do the arguments link relationships to the correct Physics?
• Is evidence synthesised across sources rather than reported one source at a time?
• Does the conclusion answer the RQ and retain the necessary scientific reasoning?

Evaluating

• Are credibility, bias, relevance, accuracy and recency considered where material?
• Is evidence quality distinguished from evidence limitation?
• Does the claim evaluation extrapolate only credible supported findings?
• Do improvements address limitations and extensions investigate a new relevant scope?

Frequently asked questions

How many sources do I need for Physics IA3?

QCAA does not prescribe a fixed number. Use enough relevant sources to support every part of the research question and to evaluate the quality of the evidence. More sources do not help if each is analysed superficially.

Do all sources need to be peer reviewed?

No. The current sample instrument recognises scientifically credible books, podcasts, science publications, government and university material, independent research bodies, manufacturers and journals. Judge whether each source and its evidence are suitable for the inference you use it to support.

Can two studies answer different parts of my question?

Yes. Complementary evidence can be powerful when you explain how the strands combine into one answer. Do not leave the synthesis for the marker to infer.

Is source credibility enough for the Evaluating criterion?

No. You also need to discuss the quality and usefulness of the evidence, extrapolate credible findings to the claim, and propose considered improvements or extensions.

Should the conclusion answer the claim directly?

First answer the research question. Then apply that scoped conclusion to the claim, clearly identifying what can and cannot be extrapolated.

Continue your Physics IA3 review

• Review evidence limitations versus source credibility.
• Distinguish improvements from extensions in QCE Science.
• Build the subject knowledge through the QCE Physics study guide.
• Compare primary-data reasoning in the Physics IA2 Student Experiment guide.
• Use Sylligence assignment feedback and select Physics IA3 Research Investigation.

Sources and methodology

Official QCAA documents control the assessment requirements. This guide was checked against the current Physics 2025 v1.3 General senior syllabus, the Physics IA3 sample assessment instrument, the Physics 2025 subject report and the QCAA Physics subject page.

Sylligence also reviewed a privately supplied Physics IA3 response that the student confirmed received full marks. The example above is paraphrased and anonymised. It illustrates a possible evidence architecture, not an official QCAA exemplar, required topic, fixed structure or guaranteed result.