$A$ hot body will radiate heat most rapidly if its surface is

Heat energy is incident on the surface of a material at the rate of $1000 \ J \ min^{-1}$. If the coefficient of absorption is $0.8$ and the coefficient of reflection is $0.1$,then the amount of heat energy transmitted through the material in $5$ minutes is: (in $J$)

$A$ body,which emits radiations of all possible wavelengths,is known as

The absorption coefficient value of a perfect black body is

What is radiation and radiant energy?

Good absorbers of heat are