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THERMAL RADIATION

THERMAL RADIATION. Definition of Thermal Radiation. This is how heat energy moves from a hot to cold region by means of electromagnetic radiation. Thermal radiation is also called infra-red or IR radiation. Properties of thermal radiation. Radiation travels equally in all directions.

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THERMAL RADIATION

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  1. THERMAL RADIATION

  2. Definition of Thermal Radiation This is how heat energy moves from a hot to cold region by means of electromagnetic radiation. Thermal radiation is also called infra-red or IR radiation. web site: www.ktaggart.com

  3. Properties of thermal radiation • Radiation travels equally in all directions. • Radiation travels far more quickly than the other forms of heat transfer. • Radiation is the only type of heat transfer that can travel through a vacuum. • Radiation travels best through a vacuum where its speed is that of light (300 000 km/s or 186 000 miles per second). • Gases tend to allow radiation through better than liquids, liquids better than solids. web site: www.ktaggart.com

  4. Detecting thermal radiation • We can feel thermal radiation with our skin. • A thermopile is a device that converts thermal radiation into electricity • Special cameras can be used to take infra-red pictures (Thermal Camera Pictures) web site: www.ktaggart.com

  5. Thermal radiation & temperature • All objects above absolute zero (-273 oC) give off thermal radiation. • The hotter an object the more radiation it gives off. web site: www.ktaggart.com

  6. Surface and emission • Darker surfaces emit radiation better than bright surfaces. • Rough surfaces emit radiation better than polished surfaces. web site: www.ktaggart.com

  7. Absorption & Reflection • Dark surfaces absorb radiation better than bright surfaces. • Polished surfaces reflect radiation better than rough surfaces. web site: www.ktaggart.com

  8. Silvered surfaces • A metal kettle, a firefighter and a marathon runner make use of silvered surfaces. web site: www.ktaggart.com

  9. The Greenhouse The ‘Greenhouse Effect’ is where gases such as carbon dioxide in the Earth’s atmosphere have the same effect as the glass of a greenhouse. web site: www.ktaggart.com

  10. Question 1 Choose appropriate words to fill the gaps in the paragraph below: Thermal radiation, also known as __________ radiation, is how heat travels by _____________ radiation. It travels equally in all ________and most quickly through a __________ where its speed is ___________ km/s. All objects above absolute zero ( ________ oC ) give off thermal radiation. Hot, _______ and rough surfaces emit radiation best. Bright and ___________surfaces reflect radiation best. web site: www.ktaggart.com

  11. Question 2 • Explain why • heat from the Sun can only reach us by thermal radiation, • in hot countries houses are often painted white, • car radiators are black, • solar cells are black. web site: www.ktaggart.com

  12. Simulations Thermal Camera Pictures- falsted Energy House Simulation. For instructions click here. web site: www.ktaggart.com

  13. Puzzles Radiation Crossword – by KT Radiation Fallen Phrase Puzzle – by KT web site: www.ktaggart.com

  14. Related Presentaions Thermal Conduction Powerpoint by KT Convection Powerpoint by KT Evaporation Powerpoint by KT Heat Energy Transfer Powerpoint by KT web site: www.ktaggart.com

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