Investigating infrared radiation

In a nutshell

By filling a Leslie cube with water, the infrared intensity of the cube's different surfaces over time will be measured using a infrared detector. This corresponds to the amount of infrared radiation radiated by the surfaces of the cube.

Equipment list

The following equipment list can be used to conduct the experiment to investigate infrared radiation radiated.

Equipment	Use
Leslie cube (a cube with different surfaces)	To show the thermal radiation radiated by different surface.
Infrared detector	To measure the infrared radiation given off by the surfaces.
Kettle	To boil the water before pouring it in the cube.
Heatproof mat	To place the beaker on in order to prevent heat escaping from the bottom of the beaker.
Stopwatch	To time the experiment.
$30\,cm$ ruler	To measure the distance between the infrared detector and the side of the Leslie cube.

Experimental variables

The independent variable is the variable you change. The dependent variable is the variable that changes depending on the other variables, and is the one you measure. The control variables are the variables that are kept constant.

Independent Variable	$Side\ of\ the\ Leslie\ cube$
Dependent Variable	$Infrared\ intensity$
Control Variables	$Distance\ between\ the\ infrared\ detector\ and\ the\ Leslie\ cube$

Safety precautions

When performing experiments, it is very important to consider safety precautions. This is so that no one gets hurt or injured during the experiment.

Hazard	Risk	Safety masure
Hot water	The water will be near boiling temperature when it is poured into the Leslie cube. This could cause burns if spilt on someone.	Don't rush when pouring the water. If burnt, run the burn under cold running water for five minutes.
Water and electronics	Spilled water on the infrared detector may result in an electric shock.	Keep the infrared detector away from water.

Method

These are the instructions to complete the experiment. Record all measurements taken as you work through the experiment in a table.

Physics; Physics practicals; KS4 Year 10; Investigating infrared radiation

1.	Heatproof mat
2.	Shiny silver
3.	Matte black
4.	Leslie cube
5.	Matte white
6.	Shiny black
7.	Ruler
8.	Infrared detector

1.	Set up the apparatus as shown in the diagram. Make sure the detector is $20\,cm$ away from the cube
2.	Boil the kettle. Fill the Leslie cube with the just boiled water.
3.	Leave the Leslie cube for a minute to give the surfaces time to be heated by the water.
4.	Measure the intensity of infrared radiation radiated from each surface using the infrared detector. Tip: If you can find four $30\,cm$ rulers, you can place these on every side of the cube so you can quickly move the detector to the $20\,cm$ mark when recording the temperature.

Analysis

This is how you will use the data recorded to form conclusions.

1.	Plot a bar chart of infrared intensity (units of $W/m^{2}$ ) for each surface.
2.	Compare the height of the bars to each other with how radiation emitted depends on the surface of an object. A black matte surface emits the most infrared radiation, whilst a shiny silver surface emits the least.

Conclusion

Physics; Physics practicals; KS4 Year 10; Investigating infrared radiation

The bar chart of the results taken during the experiment should look similar to this. The black matte surface should emit the most infrared radiation, followed by the shiny black, white matte then shiny surface.

Evaluation

Once you have completed your experiment, it is important to consider how it could be improved. You should come up with ways to improve the accuracy of your values. If you got a result that seems unreasonable, think about why this was.