The absorption coefficient of an open window is:

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

If a black body at $400 \ K$ surrounded by atmosphere at $300 \ K$ has a rate of cooling '$R_0$',the same body at $900 \ K$,surrounded by the same atmosphere,will have a rate of cooling nearly:

If there were no atmosphere on Earth,its temperature would be ...... .

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 $J$)