Emissivity of a black body is

Correct option is C

The correct answer is (C) 1.00

Explanation:
• Emissivity ($ε$) is a measure of an object's ability to emit infrared energy compared to a perfect black body at the same temperature.
• A 'Black Body' is a theoretical idealized physical body that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence.
• Because it is a perfect absorber, it must also be a perfect emitter of radiation to maintain thermal equilibrium.
• Therefore, by definition, the emissivity of a perfect black body is 1.00.
• All real objects have emissivities between 0 and 1. For example, soil typically has an emissivity between 0.90 and 0.98.

Information Booster:
• Kirchhoff's Law of thermal radiation states that for an arbitrary body in thermal equilibrium, the emissivity equals the absorptivity ($ε = α$).
• Objects with low emissivity, like polished metals, reflect most of the radiation and emit very little.
• The Stefan-Boltzmann Law ($E = σ T^4$) describes the power radiated from a black body.

Additional Knowledge:
• 0.00 (Not listed): This would be a 'perfect reflector' or a white body.
• Gray bodies: Objects that have a constant emissivity less than 1.0 across all wavelengths.