The total emissivity power is defined as the total amount of radiation emitted by a black body per unit

Answer: Option C

Total emissive power refers to the total amount of thermal radiation emitted by a surface (typically a black body) across all wavelengths per unit time and per unit area.

This concept is governed by Stefan-Boltzmann law, which states:

E = σT⁴

Where:
E = Total emissive power
σ = Stefan-Boltzmann constant
T = Absolute temperature of the black body

As per the definition, the total emissive power is expressed in units of watts per square meter (W/m²), indicating that it is radiation emitted per unit area.

Therefore, the correct answer is: Area (Option C).