The cooling rate of a sphere at $600\,K$ in an external environment of $200\,K$ is $R$. When the temperature of the sphere is reduced to $400\,K$,the cooling rate of the sphere becomes:

The temperature of a black body increases from $327^{\circ}C$ to $927^{\circ}C$. If the initial energy possessed is $2 \ kJ$,what is its final energy in $kJ$?

The wavelength of maximum intensity of radiation emitted by a star is $289.8 \ nm$. The radiation intensity of the star is (Stefan's constant $= 5.67 \times 10^{-8} \ W m^{-2} K^{-4}$,Wien's constant $b = 2898 \ \mu m \ K$).

$A$ black rectangular surface of area '$A$' emits energy '$E$' per second at $27^{\circ} C$. If length and breadth are reduced to $\frac{1}{3}$ of their initial values and the temperature is raised to $327^{\circ} C$,then the energy emitted per second becomes:

$A$ planet of radius $R_{p}$ is revolving around a star of radius $R^{*}$ which is at temperature $T^{*}$. The distance between the star and the planet is $d$. If the planet's temperature is $f T^{*}$, then $f$ is proportional to

$A$ black body at $227^o C$ radiates heat at the rate of $7 \; cal/cm^2 s$. At a temperature of $727^o C$,the rate of heat radiated in the same units will be: