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Year 11 - Science

Emitting infrared and black body radiation

Electromagnetic waves

Unit Summary

This unit explores reflection, refraction, and lenses using ray diagrams. It covers the electromagnetic spectrum, light as a wave, absorption, transmission, and practical uses. Emphasis is on risks, temperature balance, data presentation, and unit conversions.

Lesson Summary

You will learn to describe how to investigate the emission of infrared radiation by different surfaces and explain what is meant by a 'black body' radiator.

Key Notes

  • 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.

Vocabulary To Learn

  • 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.

Common Mistakes To Avoid

  • White surfaces are always poor absorbers of visible light so they must also always be poor absorbers and emitters of infrared.

3 Quick Questions (With Answers)

1. Explain the scientific idea in this lesson using two key 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.

2. Define this scientific word and use it in context. 'infrared radiation'

Infrared radiation means electromagnetic waves with frequencies in a range just lower than for red light. Include the word in a full scientific explanation, not as a single label.

3. Correct this common scientific misunderstanding.

Mistake: White surfaces are always poor absorbers of visible light so they must also always be poor absorbers and emitters of infrared. Correction: 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.

More Lessons In This Unit

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