Factors affecting emissive power The total emissive power of a real surface depends on which of the following parameters?

Introduction / Context:
Emissive power characterizes how much thermal radiation a surface emits. For real (non-black) bodies, several variables influence emission.

Given Data / Assumptions:

• Real surface, not an ideal blackbody.
• Spectral behavior matters (dependence on wavelength).

Concept / Approach:
Blackbody emission depends only on temperature (E_b = σT^4). Real surfaces have emissivity ε that depends on wavelength, temperature, and surface condition (oxidation, roughness, finish), so E = ε(λ,T,material) * σT^4 (integrated over spectrum).

Step-by-Step Solution:
Recognize temperature drives the σT^4 magnitude.Acknowledge physical nature (polished vs. oxidized) alters ε.Wavelength dependence means spectral emissive power varies across λ.

Verification / Alternative check:
Spectral emissivity charts show strong dependence on wavelength and surface finish for metals and ceramics.

Why Other Options Are Wrong:

• Single-factor choices ignore the multidimensional dependence.
• “Area only” is irrelevant to per-unit-area emissive power.

Common Pitfalls:
Assuming a constant ε across all wavelengths; using blackbody assumption for shiny metals, leading to large errors.

Final Answer:
all of these