Radiation and Absorption
Investigate how the surface of a material affects how much heat it emits or absorbs.
Check your understanding with these quick common questions. Use the drop down boxes to see the correct answers.
Infra red - Radiation and absorption
Most students do not realize that infra red transfers heat energy. Most students also confuse how different colours
Independent variable - Colour of surface, e.g. black, silver
Dependent: temperature change / time taken to cool.
Control: same starting temperature, voume of water
Different objects might be used
Sometimes a leslie cube is used. This has four different coloured surfaces. This can be better because the volume of water is identical in all four surfaces.
An infrared dector measures how much infra red is given out. Sometimes this is converted into a temperature. Be careful, its not the same as a thermometer.
Accuracy can be improved by: Using a leslie cube ensures all surfaces have identical volumes and temperature of water inside. Using a digital thermometer will give a more accurate measurement. .
Other improvements: Repeat and calculate a mean.
Lots of people get this wrong!
Black both absorbs AND emits heat the fastest. (think of it like a net, lots of gaps so heat can move easily through it)
SIlver/White absorbs and emits heat the slowest (think of it like a shield so it does not let anything through).
The misconception is that black heats up the easiest BUT does not give out heat. This is wrong. It emits AND absorbs the fastest.
There is no fornula required for this practical.
This practical could come in a range of variations. The method below is a guide for using a leslie cube.
Fill Leslie cube with hot water using a measuring cylinder
Measure starting temperature/emission from each face with infrared sensor.
Make sure the starting temperature is the same for each trial. Use a thermometer to control this.
Measure either the emission of infra red given out with a infra red detector.
(some questions might investigate cooling of an object, so in this case use a thermometer
Compare black, white, shiny surfaces.