Blackbody Radiation PHY361, 20080114

1
Blackbody Radiation PHY361, 2008-01-14

• review overview of Classical Statistical
  Mechanics
• kinetic theory HEAT is random kinetic energy
  (thermal motion) of atoms
• IDEAL GAS law PV N kT
• EQUIPARTITION theorem 1/2 kT energy per DoF
  (degree of freedom)
• k heat capacity amount of heat energy needed
  to raise the temperature
• eg. Maxwell-Boltzman distribution of molecular
  velocity in a gas
• density of states g(E) of states
  (momentum vectors, etc)
• distribution function f(E) of particles in
  each state fB exp(-E/kT)
• blackbody radiation catastrophic failure of
  classical stat. mech.
• what is blackbody radiation?
• Stefan-Boltzman law R ? T4
• Wiens displacement law ?mT 2.89810-3 mK
• Rayleigh-Jeans equation u(?) 8??kT ?-4
  UV Catastrophe
• Plancks law u(?) 8? hc
  ?-5 / (exp(hc/? kT) -1)Plancks constant h

2
(No Transcript)
3
(No Transcript)
4

• IR heat lamp
• red hot
• silver heat shield

5
(No Transcript)
6

• Stefan-Boltzman law R ? T4
• Wiens displacement law ?mT 2.89810-3 mK
• Rayleigh-Jeans equation u(?) 8??kT ?-4
  UV Catastrophe
• Plancks law u(?) 8? hc
  ?-5 / (exp(hc/? kT) -1)