Physics SL IA ideas: clean experiments with real-world conclusions
Run a pilot before planning the full Physics dataset
For a pendulum investigation, define length from the pivot to the bob's centre and use a small release angle consistent with the simple model. Timing several oscillations can reduce the relative effect of a start/stop timing error, but repeated trials do not remove a systematic error in the measured length.
- Choose a safe apparatus and obtain teacher approval.
- Keep the release method and timing convention consistent.
- Record repeated observations rather than only an average.
- Explain how uncertainty changes the strength of your conclusion.
From ten oscillations to one period
In an illustrative trial, ten oscillations take 15.8 seconds. The estimated period is 1.58 seconds. If the uncertainty on the total interval is ±0.2 seconds, dividing that interval by ten gives ±0.02 seconds per period for that timing contribution. This does not include every uncertainty in the investigation, and ten oscillations is an example method—not a universal IB requirement.
Compare the HL model-testing ideas, check the evaluation framework and use the topic feasibility test before scaling up the experiment.
IA weighting and scoring criteria
The Physics SL IA is a scientific investigation. The investigation should be controlled, quantitative and uncertainty-aware, with a conclusion that is supported by the data rather than only by the expected theory.
Focused question, variables, controls, reproducible method, safety/environmental notes and a setup that produces quantitative data.
Raw and processed data, uncertainty, sample calculations, model fitting, gradients and appropriate significant figures.
Direct answer to the question, comparison with theory and interpretation supported by the graph and uncertainty.
Specific weaknesses, their effect on results, realistic improvements, strengths and possible extensions.
A strong Physics SL IA is built from a visible relationship that can be measured well. You do not need an extreme apparatus. You need a focused research question, controlled variables, clear raw data, uncertainty, a theory graph and a conclusion that says something useful.
The attached guide chooses SL topics that are safe, observable and strong for data quality. Each one has a practical point: solar panel alignment, light blocked by polarization, or sound reduction through materials. That makes the conclusion more meaningful than simply saying the theory was correct.
What a strong IA in this subject shows
Choose an experiment where you can control distance, angle, material, frequency, brightness or load. Use repeated measurements and keep the setup fixed except for the independent variable. Your graph should test a relationship from theory, not just display raw data. The evaluation should name specific limitations: sensor precision, alignment error, background light, lamp heating, reflections, gaps around materials or phone-app calibration.
Three go-to Physics SL IA ideas
1. Solar panel angle and maximum power output
This is practical and satisfying because a small panel becomes a real energy system: rotate it, measure power, then calculate how much misalignment costs.
Research question: How does the angle of a solar panel affect the electrical power delivered to a fixed load, and what angle gives the highest measured output?
Use a small solar panel, lamp or sunlight, protractor, voltmeter, ammeter and fixed resistor/load. Measure voltage and current at different panel angles, then calculate delivered electrical power. The theory predicts that output should fall roughly with the cosine of the angle if light intensity on the panel decreases with projected area. The useful conclusion is not just the best measured angle; calculate the tolerance range where power remains above 90% of the measured maximum and the percentage loss at common misalignment angles. Do not call this conversion efficiency unless incident optical power is also measured.
IB topics used: energy, electric power, waves/light, cosine relationship, uncertainty
Data to collect: Voltage, current and calculated power at controlled panel angles with fixed light distance and load.
Diagram to include: Panel rotated relative to incoming light, with angle theta and power-angle graph.
2. Polarized sunglasses and screen brightness
This is a visually dramatic IA: rotate the polarizer and the screen fades. The mathematics turns that visible effect into Malus' law.
Research question: How does the angle between polarized sunglasses and a phone screen affect transmitted light intensity?
Use a phone or laptop screen as a light source, place polarized sunglasses or a polarizing filter over it, and measure brightness at fixed rotation angles using a light meter or sensor app. Keep screen brightness, distance and background light constant. Compare the relative intensity with the square-cosine prediction. A strong conclusion calculates the angle that halves intensity and the percentage of light blocked at different angles, connecting the experiment to sunglasses, LCD screens, privacy filters and photography.
IB topics used: polarisation, waves, light intensity, Malus' law, percentage uncertainty
Data to collect: Relative light intensity at set rotation angles, collected in a controlled light environment.
Diagram to include: Screen, rotating polarizer and sensor, plus a cos squared curve overlaid with data points.
3. Sound insulation and material thickness
This is useful because the final answer can recommend the best material per centimetre, not just the thickest material.
Research question: How does the thickness of an insulating material affect sound level reduction?
Use a speaker playing a constant tone and measure decibel level after sound passes through foam, fabric, cardboard, felt or layered materials. Keep the speaker volume, frequency, microphone distance and geometry fixed. Calculate sound reduction in decibels, then convert decibel changes into intensity ratios to show what the reduction means physically. The best version compares reduction per centimetre of thickness so materials can be judged fairly. Discuss reflections, background noise, gaps around the material and phone-app calibration as limitations.
IB topics used: sound waves, decibels, intensity, materials, uncertainty
Data to collect: Decibel level through different material thicknesses at a fixed frequency and distance.
Diagram to include: Speaker, insulation layer and microphone in a fixed line, plus reduction versus thickness graph.
How to choose from these ideas
Choose the investigation where you can collect the cleanest data, not the one with the most dramatic title. A high-scoring IA usually has one clear independent variable, one meaningful dependent variable, enough repeats, a sensible model and an evaluation that admits what the data cannot prove. Before starting, confirm your exact subject guide, safety rules and teacher expectations.
Sources checked
- IB Physics in the DP
- IB Physics subject brief
- IB 2026 Physics examiner instructions
- IB assessment and exams
Editorial review
Reviewed against the cited official IB subject and assessment sources. This article provides planning examples, not examiner advice or ready-to-submit coursework.
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