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.
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.
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 its power output, and what angle gives maximum efficiency?
Use a small solar panel, lamp or sunlight, protractor, voltmeter, ammeter and resistor/load. Measure voltage and current at different panel angles, then calculate 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 angle; calculate the tolerance range where power remains above 90% of maximum and the percentage loss at common misalignment angles.
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.
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.
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.
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.
