Infrared radiation absorption and radiation by a surface - AQA
The amount of infrared radiation absorbed or radiated by a surface depends on the nature of that surface. The Earth’s temperature also depends on the rates at which light radiation and infrared radiation are absorbed and emitted by the Earth’s surface and atmosphere.
Required practical - how different surfaces affect infrared intensity
Investigate how the amount of infrared radiation absorbed or radiated by a surface depends on the nature of that surface
There are different ways to investigate the amount of infrared radiation absorbed or radiated by a surface. It is important to:
use appropriate apparatus to measure and record temperature accurately
make observations regarding the effects of electromagnetic waves on different substances
The method described here uses a Leslie cube. This is a metal cube with four different types of surface. It is filled with hot water to increase its temperature.
Aim of the experiment
To investigate how the amount of infrared radiation absorbed or radiated by a surface depends on the nature of that surface.
Place a Leslie cube on a heat-resistant mat. Fill it, almost to the top, with boiling water and replace the lid.
Leave for one minute. This is to enable the surfaces to heat up to the temperature of the water.
Use the infrared detector to measure the intensity of infrared radiation emitted from each surface, or the temperature of the surface. Make sure that the detector is the same distance from each surface for each reading.
Record results in a suitable table. The table below shows some example results:
Infrared intensity (W/m2)
Plot a bar chart to show the results. Make sure each bar is the same width and labelled clearly to show which surface it represents.
Use your results to order the different surfaces from the best emitter to the worst emitter of infrared radiation.
Explain why the detector must be placed the same distance from each surface before taking a reading.
Hazards and control measures
Pour water slowly, using a funnel if necessary. Do not move the Leslie cube until it has cooled.