Thermal radiation fundamentals: which statements describe an ideal (perfectly) black body's absorption and emission characteristics?

Introduction / Context:
A perfectly black body is a theoretical construct in thermal radiation and remote sensing. It absorbs all incident electromagnetic radiation and, at thermal equilibrium, emits a characteristic spectrum (Planck distribution). Understanding its properties is crucial for interpreting sensor radiances and calibrations.

Given Data / Assumptions:

• Black body has emissivity ε = 1 at all wavelengths and directions.
• Diffuse emission means radiance follows Lambert’s cosine law, independent of viewing direction.
• Emission spans all wavelengths with intensity depending on temperature.

Concept / Approach:
By definition, a black body absorbs 100% of incident radiation (no reflection or transmission). Kirchhoff’s law links absorptivity and emissivity; an ideal black body is also an ideal emitter. Its spectral exitance follows the Planck function, covering all wavelengths, with peak shifting per Wien’s law.

Step-by-Step Solution:
Confirm absorption: a black body absorbs all incident radiation.Confirm emission: it emits across the spectrum; the distribution depends on temperature.Confirm diffuse behavior: idealized black surfaces are modeled as Lambertian (diffuse) emitters with directionally uniform radiance.Hence, all listed statements are consistent with the ideal model.

Verification / Alternative check:
Radiometry texts describe black bodies as perfect absorbers and emitters; laboratory blackbody sources approximate this for sensor calibration.

Why Other Options Are Wrong:

• Any single statement alone is incomplete; black body properties include all three aspects.

Common Pitfalls:

• Confusing 'black paint' with a physical black body; real materials have ε < 1 and may not be perfectly diffuse.

Final Answer:
All the above