Black Body Radiation

• Black Body Radiation


  Complicated but can be understood with time
• Black Bodies


  • They are the ultimate emitters
  • They absorb all the radiation that hits them
  • No radiation is reflected or transmitted
• As good absorbers are also good emitters, perfect black bodies are the best possible emitters of radiation
• All objects emit electromagnetic (EM) radiation due to the energy in their thermal energy stores
• The intensity and distribution of the wavelengths emitted by an object depend on the object's temperature
• Intensity


  The power per unit area, i.e. how much energy is transferred to a given area in a certain amount of time
• As the temperature of an object increases


  The intensity of every emitted wavelength increases
• As the temperature of an object increases


  The intensity increases more rapidly for shorter wavelengths than longer wavelengths
• As the temperature of an object increases


  The peak wavelength (the wavelength with the highest intensity) decreases
• Curves on the graph


  • Show how the intensity and wavelength distribution of a black body depends on its temperature
• Hotter objects have a peak wavelength that is shorter than cooler objects