Emitters of infrared & black body radiation
I can describe how to investigate the emission of infrared by different surfaces, state what is meant by a ‘black body’ radiator and explain how radiation affects an object’s temperature.
Emitters of infrared & black body radiation
I can describe how to investigate the emission of infrared by different surfaces, state what is meant by a ‘black body’ radiator and explain how radiation affects an object’s temperature.
Lesson details
Key learning points
- All bodies (objects) of all temperatures emit and absorb infrared radiation. Hotter bodies emit more IR in a set time.
- The range of wavelengths emitted, and their intensities, depend on an object’s temperature.
- Good absorbers (e.g. dark and dull surfaces) are also good emitters. Shiny metal surfaces are poor absorbers/emitters.
- A black body is a theoretical object that absorbs all of the radiation that falls on it.
- The temperature of a body depends on the rates at which radiation is absorbed and emitted.
Common misconception
White surfaces are always poor absorbers of visible light so they must also always be poor absorbers and emitters of infrared.
White paint is a good absorber and emitter of IR. Colour is not always a good guide to effectiveness at emitting/absorbing IR, except for dark+dull surfaces usually being good emitters/absorbers and shiny metal surfaces being poor emitters/absorbers.
Keywords
Infrared radiation - Infrared radiation means electromagnetic waves with frequencies in a range just lower than for red light.
Emit - To emit infrared radiation is to give out infrared radiation.
Temperature - The temperature of an object measures how hot or cold it is.
Leslie cube - A Leslie cube is a hollow metal cube that can be filled with hot water. Each side has a different colour and finish so emits different intensities of infrared radiation.
Black body - A black body is a theoretical object that absorbs all of the radiation that falls on it.
Equipment
Detailed in the Additional Materials (teacher and technician notes) for this lesson.
Content guidance
- Risk assessment required - equipment
Supervision
Adult supervision required
Licence
This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).
Video
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Starter quiz
6 Questions
The maximum displacement of a wave from the rest position.
The number of wavelengths passing a point each second.
A regular, repeating forwards–and–backwards movement.
Distance between two equivalent points on neighbouring wavelengths.
Exit quiz
6 Questions
control variable
dependent variable
independent variable
This variable affects the rate of energy transfer.
This variable affects temperature change when energy is transferred.
This reduces energy transfer by evaporation.
sometimes a good and sometimes a poor absorber
usually a poor absorber
usually a good absorber