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- Subject
- Heat Transfermechanical-engineering-mcqs › heat-transfer
- Published
- 24 Jan 2019
- Last updated
- 28 May 2026
Explanation
Since the surface reflects 40% and transmits 15% of the incident radiant energy, the remaining portion must be absorbed. Emissivity is equal to absorptivity for a surface in thermal equilibrium, so emissivity = 1 - (reflectivity + transmissivity) = 1 - (0.40 + 0.15) = 0.45.
More Heat Transfer MCQs
Practice related questions from the same subject.
- 1.According to Wien's displacement law, the wavelength at which a blackbody emits maximum radiation is directly related to which of the following?
- 2.Under what condition, based on radiative characteristics, is a material considered opaque?
- 3.Under which condition based on radiative characteristics does an object appear white?
- 4.Which principle states that the ratio of a body's emissive power to its absorptive power is constant for all materials and equals the emissive power of an ideal black body?
- 5.How do the thermal diffusivities of solids typically compare to those of liquids and gases?
- 6.According to Stefan's law, the total energy radiated per second per unit area by a black body is directly proportional to which of the following?
- 7.Under which conditions related to radiative properties is a body considered black?
- 8.The total emissive power refers to the total radiation energy emitted by a black body per unit of what?
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