Planck spectrum and electromagnetic mode counting
Thermal radiation in a vacuum cavity at temperature T has spectral energy density per angular frequency u_ω=ħω³/[π²c³(exp(ħω/(k_BT))−1)].
Key knowledge
Thermal radiation in a vacuum cavity at temperature T has spectral energy density per angular frequency u_ω=ħω³/[π²c³(exp(ħω/(k_BT))−1)]. This combines two transverse photon polarizations, vacuum dispersion and Bose occupation with zero photon chemical potential.
Values and equations
u_ω=ħω³/[π²c³(e^[ħω/(k_BT)]−1)]
- u_ω
- Energy density per angular frequency J s m⁻³
- ω
- Angular frequency rad s⁻¹
- ħ
- Reduced Planck constant J s
- c
- Vacuum light speed m s⁻¹
- k_B
- Boltzmann constant J K⁻¹
- T
- Temperature K
Conditions and scope
- Equilibrium blackbody cavity, vacuum dispersion and T>0; u_ω dω is energy per volume in an angular-frequency interval.
- Frequency, wavelength and directional radiance spectra have different Jacobians; this excludes vacuum zero-point energy and is not every material's emission spectrum.
Sources · 1
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Thermodynamics and Statistical Mechanics (2016): Planck radiation law: Equations 8.103–8.118: dispersion, two-polarization mode density and Planck spectrum; excludes erroneous figure-scale expression ω₀=kT₀/k.
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Entry details
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