Summary of Thursday September 8

Electromagnetic Radiation

• plot of emission versus wavelength

Total emission proportional to temperature to the 4th power

• double temperature gives 16 times as much energy

Kirchhoff's Law: emissivity = absorptivity (for same wavelength)

• blackbody - perfect emitter

Wien's Law: Wavelength of maximum emission times temperature is constant:

• LmaxT = const
• higher temperature objects give off shorter wavelengths
• hotter bodies radiate more energy at all wavelengths

Reflection of Radiation - Albedo

• various examples given
• water high with low sun, low with high sun