$A$ thermos flask is polished well.

Which of the following is closest to a black body?

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

The spectrum of black body radiation is a

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 $J$)

$A$ certain substance emits only the wavelengths ${\lambda _1}, {\lambda _2}, {\lambda _3}$ and ${\lambda _4}$ when it is at a high temperature. When this substance is at a colder temperature,it will absorb only the following wavelengths: