Why if a hot object did not emit radiation then second law of thermodynamics would be violated?
Every body in the universe emits and absorbs radiation.As far as heat flow is considered it takes place in the direction of hotter to colder body if no external work is done .The 2nd Law of Thermodynamics basically gives the direction of natural(irreversible) process which is the increase in entropy.so your hot body will radiate more than it absorbs if no work is done externally.
If a hot object did not emit radiation but could nonetheless absorb radiation then it would gain heat from a cooler body that did radiate. That would be a 2nd law violation.
A perfect white body does not violate thermodynamics. It would neither emit nor absorb any radiation, but simply reflect it.
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