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 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)