Emitting infrared radiation
I can describe how to investigate the emission of infrared radiation by different surfaces.
- Year 11
- AQA
Emitting infrared radiation
I can describe how to investigate the emission of infrared radiation by different surfaces.
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.
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.
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.
Equipment
Detailed in the Additional Materials (teacher and technician notes) for this lesson.
Content guidance
- Risk assessment required - equipment
Supervision
Adult supervision required
Licence
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.Which of the following is not a type of electromagnetic radiation?
Q2.Which of the following types of electromagnetic radiation are emitted by a hot light bulb?
Q3.Surfaces can absorb radiation. Which of the following words or phrases is closest in meaning to the word absorb?
Q4.Which of the following statements about infrared radiation are correct?
Q5.Match up the following key terms about waves with their definitions.
Q6.Which of the following statements about thermal conduction are correct?
Assessment exit quiz
6 Questions
Q1.A pupil has test tubes of hot water covered in different colours of paper. He investigates whether colour affects the rate of infrared emission. Match each variable with its type in this experiment.
Q2.A pupil has beakers of hot water covered in different colour paper to investigate how colour affects temperature drop caused by infrared energy transfer. Match the parts of her method with the reason.
Q3.An infrared thermometer may show different temperature readings for two objects that are at the same temperature. Which of the following is a possible explanation?
Q4.Match the following types of surface to the description of how well it absorbs infrared radiation.
