A Leslie cube is used to compare surfaces. State which surface emits the most infrared radiation, and name one variable that must be kept constant.
[2 marks]
Total for this question: 2
Physics required practicals
Infrared radiation and surfaces
AQA 4.6 · RP10
GCSE Physics (8463) · Required practical 10 — method, variables, the marks examiners report students losing.
Board and spec code confirmed against AQA 8463 · registry checked 2026-07-17How this checking works
Investigate how the amount of infrared radiation absorbed or emitted by a surface depends on the nature (colour and shininess) of that surface.
Apparatus
- Leslie cube with faces of different surfaces (matt black, shiny silver, white, dull grey)
- Kettle or hot water to fill the cube
- Infrared detector (thermopile) or a thermometer with a blackened bulb
- Ruler to fix the distance from cube to detector
- Heatproof mat and safety goggles
Method
- 1Fill the Leslie cube with very hot (near-boiling) water and stand it on a heatproof mat.
- 2Place the infrared detector a fixed distance from one face and record its reading (or the temperature rise over a set time).
- 3Rotate the cube to face the detector with each surface in turn, keeping the same distance and time.
- 4Record the detector reading for each surface.
- 5(Absorption version: point an infrared heater at metal plates with different surfaces at equal distances and record the temperature rise of each.)
Variables
Independent
The type of surface (matt black, shiny, white, dull)
Dependent
The amount of infrared radiation emitted (detector reading or temperature rise)
Control
- Distance from the cube face to the detector
- Temperature of the water and the time taken
- The same detector
Results & processing
- Matt black surfaces emit (and absorb) the most infrared radiation; shiny silver surfaces emit and absorb the least.
- Record detector reading (or temperature rise) against surface type in a table and compare.
Where students lose marks
Changing the distance between the cube face and the detector.
Fix: Keep the distance the same for every face, because infrared intensity falls with distance.
Using different water temperatures or times.
Fix: Fill the cube once and take all readings quickly, so every face starts at the same temperature.
Touching or leaning on the cube.
Fix: Handle it only by the lid; touching a face transfers heat by conduction and warms the detector directly.
Improve the method
- Keep the detector the same fixed distance from each face.
- Take all readings from the same filling of hot water, before it cools noticeably.
- Use a thermopile and data logger, shield from draughts, and repeat the readings.
Try it — exam-style
Easy
ORIGINAL
Medium
ORIGINAL
Explain why the distance between the detector and each face of the cube must be kept the same.
[2 marks]
Total for this question: 2
Questions are written in the style of past AQA papers — never copied from them.
Drill it properly
Stuck on infrared radiation and surfaces?
This practical is a fair-test question about surfaces — I drill the control variables and the black-body result. Free intro call, then a free first lesson.