gcse science a physics 1 waves learning outcomes identify thermal radiation with electromagnetic...
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WavesWavesLearning Outcomes
• Identify thermal radiation with electromagnetic radiation.
• Describe the greenhouse effect in terms visible radiation from the sun, and infra-red from the earth.
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Key Words:
• Electromagnetic Spectrum: The collective name for radio waves, microwaves, infrared etc...
• Wavelength: The “length” of one complete wave.
• Frequency: The number of complete waves passing a point per second.
• Amplitude: The height of the wave
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WavesWavesWhich colour’s hotter?
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You will have noticed that the colours in order of hotness were:Red -> Orange -> Yellow -> Blue -> Indigo/violet
Why isn’t there any Green?
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As we have seen; different temperature objects emit different colours of light. But it is not as simple as this;
• Hot objects emit many different types of EM radiation.
• The type they emit most of depends on their temperature.
• Objects that have temperatures similar to the surface of the earth emit mostly in the infra-red. We can’t see this unless we use a thermal-imaging camera!
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WavesWavesThe Greenhouse Effect
These three little blighters pictured on this page are responsible for the greenhouse effect. Do you know
what they are?
The greenhouse effect happens because the sun emits most of its energy as blue light, which is not
affected by greenhouse gases.The Earth absorbs this blue light and then warms up.
Because the Earth is not as hot as the sun, it emits most of its light as infrared.
Greenhouse gases reflect infrared back to the earth, warming it up even more.
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Plenary
Some people don’t believe that the greenhouse effect is real. Produce a poster informing them of the mechanism responsible, and how it works!
Why MIGHT the greenhouse effect NOT be responsible for the global warming that we are experiencing.