blackbody

Ideally, a body that would absorb all and reflect none of the radiant energy falling upon it; its reflectivity would be zero and its absorptivity (and consequently, its emissivity) would be 100%. In practice, a radiator of uniform temperature whose radiant emittance in all parts of the spectrum is the maximum obtainable from any radiator at the same temperature, or a radiator whose spectral radiant emittance conforms with Planck's law of radiation.

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