Question

Describe an experiment to show that a blackened surface is a better emitter of heat than a polished one.

Answer 1

Black body is the best emitter because if something is black, it means it's strongly coupled to electromagnetic field. A body which a good absorbed of heat is also a good emitter because absorbing is just opposite process of emitting. And also by Kirchoff's law of radiation, make it evident that a black body is not only a perfect absorbed but also a perfect emitter of heat.