1 Answer
Emissivity is a dimensionless quantity, meaning it has no units. It is a ratio of the radiation emitted by an object to the radiation emitted by a perfect black body at the same temperature. Since both the numerator and denominator are in the same units, they cancel out, leaving emissivity without any units.
So, the SI unit of emissivity is simply 1 (or it can be expressed as a pure number).
So, the SI unit of emissivity is simply 1 (or it can be expressed as a pure number).