A sphere cube and a thin circular plate all made of the same material and having the same mass are initially heated to a temperature of 300°C. which of these cools fastest?
Sphere
Cube
Plate
None of these
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A black body emissive power is 81 J/m2 sec it is at 300 K another one ordinary body emissivity is 0.8 it is at 500 K then what is the emissive power of ordinary body?