Which term describes the property of a body that relates to its emission of electromagnetic radiation?

Which term describes the property of a body that relates to its emission of electromagnetic radiation?

• A. Reflectance
• B. Absorptance
• C. Transmittance
• D. Emittance

Answer: (D)

Emittance describes how much radiant energy a body emits from its surface per unit area. It’s about the emission itself, not what happens to incoming light. The actual emitted flux depends on temperature and how effectively the surface radiates, captured by emissivity: emitted flux equals emissivity times the blackbody flux (σT^4). Reflectance, absorptance, and transmittance describe how a surface interacts with incident radiation (what is reflected, absorbed, or transmitted), not its own emission. So emittance is the term that best describes the property related to emission.

Emittance describes how much radiant energy a body emits from its surface per unit area. It’s about the emission itself, not what happens to incoming light. The actual emitted flux depends on temperature and how effectively the surface radiates, captured by emissivity: emitted flux equals emissivity times the blackbody flux (σT^4). Reflectance, absorptance, and transmittance describe how a surface interacts with incident radiation (what is reflected, absorbed, or transmitted), not its own emission. So emittance is the term that best describes the property related to emission.