Lecture 7

October 17

Radiation or What We Get From the Sun

1. Solar energy warms the earth and powers life through photosynthesis
2. Energy radiates from the sun as electromagnetic waves
   • waves, frequency, wavelength
   • electromagnetic spectrum
   • visible spectrum
3. Bodies of different temperature radiate energy of different wavelengths
   • demo - temperature of body varies as color changes
   • model system - black body
     • black body absorbs and emits electromanetic radiation without favouring a particular wavelength
     • peak wavelength is inversely proportional to temperature
     • energy emitted increases as temperture to the power of 4
   • form of spectrum is characteristic
     • description of form requires quantum picture of em radiation
4. Spectrum of solar radiation
   • peak wavelength appropriate for electronic excitation
     • photosynthesis - Ron
5. Earth's temperature
   • absorbtion of solar energy
   • reflectance of solar energy - albedo
   • emission of radiation from earth
   • greenhouse effect
     • why water and CO2 absorb short wavelength radiation - Derek
   • demo - greenhouse effect

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