Heat and Mass Transfer
Depending on the radiating properties, a body will be black when(Where a = absorptivity, p = reflectivity, X = transmissivity.)

P= 1, T = 0 and a = 0
P = 0, x = 1 and a = 0
P = 0, x = 0 and a = 1
X = 0, a + p = 0

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Heat and Mass Transfer
According of Kirchhoff's law

Emissive power and absorptivity are constant for all bodies
Ratio of emissive power to absorptive power for all bodies is same and is equal to the emissive power of a perfectly black body
Radiant heat is proportional to fourth power of absolute temperature
Emissive power depends on temperature

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