$A$ thermopile is used for:

Which of the following laws states that "good absorbers of heat are good emitters"?

If between wavelength $\lambda$ and $\lambda + d\lambda$,$e_\lambda$ and $a_\lambda$ are the emissive and absorptive powers of a body,respectively,and $E_\lambda$ is the emissive power of a perfectly black body,then according to Kirchhoff's law,which of the following is true?

Out of the following, which statement is $NOT$ true about black body radiation?

$A$ hot and a cold body are kept in vacuum separated from each other. Which of the following causes a decrease in the temperature of the hot body?

$A$ sphere,a cube,and a thin circular plate,all made of the same material and having the same mass,are initially heated to a temperature of $1000^{\circ}C$. Which one of these will cool first?