Download Blackbody Radiation

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.’
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what is blackbody radiation?
Stefan-Boltzman law:
R =  T4
Wien’s displacement law: mT = 2.898£10-3 m¢K
Rayleigh-Jeans equation: u() = 8kT -4
UV Catastrophe
Planck’s law:
u() = 8 hc -5 / (exp(hc/ kT) -1)
Planck’s constant ‘h’
• IR heat lamp
• ‘red hot’
• silver heat shield
–Stefan-Boltzman law:
R =  T4
–Wien’s displacement law: mT = 2.898£10-3 m¢K
–Rayleigh-Jeans equation: u() = 8kT -4
UV Catastrophe
–Planck’s law:
u() = 8 hc -5 / (exp(hc/ kT) -1)