: a law in physics: radiant energy arising from processes within atoms or molecules is emitted in finite quanta each of which is equal to the product of the radiation frequency by a universal constant h see planck constant
2
: a law in physics: the energy density of radiation within a blackbody cavity at absolute temperature T in terms of the wavelength λ is given by ΔPλ = ((8πhc)/λ5[ehc/(KλT) - 1]) Δλ where ΔPλ is the energy density within a given small wavelength interval Δλ, h is the Planck constant, and c the speed of light, all quantities being in cgs units
Word History
Etymology
after Max K. E. L. Planck
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