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Question:

Emissive and absorptive power of a material at 2000 K is 8 and 10 respectively. Calculate the emissivity of IBB (Ideal black body)

0.6

0.4

0.2

0.8

Solution:

Emissivity = Radiant energy of object / Radiant energy of black body
For black body, emissive power=absorptive power=10
Hence, Emissivity=8/10=0.8