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7 June, 2014. Radiation. Keywords EM-Spectrum, Speed of light, Infra-red, Leslie Cube, vacuum, reflect. Learning Outcomes: All students should be able to: Describe what radiation is. Most students should be able to:
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7 June, 2014 Radiation Keywords EM-Spectrum, Speed of light, Infra-red, Leslie Cube, vacuum, reflect
Learning Outcomes: All students should be able to: • Describe what radiation is. Most students should be able to: • Describe how fast infra-red light travels, and how different colours effect the rate how much heat is absorbed or radiated. Some students should be able to: Explain how a vacuum flask insulates so well.
Radiation • Radiation is the transfer of energy by waves • Light is radiated, sound is radiated • Heat is radiated in infra-red waves and needs no medium in which to travel. (It can travel through a vacuum)
Infrared • Infra Below
Radiation of heat energy • Heat is being radiated to us all the time by the Sun. • It’s travelled 92 million miles to reach us (150 million km) • It takes about 8 minutes to get here!!
More Radiation facts • It travels in all directions • In straight lines • Goes at the speed of light (Infrared is part of the electromagnetic spectrum) • Doesn’t need particles to transfer the energy – transferred by waves
How do colours make a difference? • Is black a good absorber of heat radiation? • Are light colours and shiny surfaces good at absorbing heat radiation?
Vacuum Flasks Parts 1 double-walled glass container 2 hot liquid 3 plastic cap 4 plastic support 5 plastic container 6 silvered surfaces 7 sponge pad 8 vacuum
Vacuum Flask • Explain how the flask slow down: • 1 Conduction? • 2 Convection? • 3 Radiation? • The vacuum stopsconduction • The cap stops convection • The silver stops radiation