Two spherical black bodies have radii $r_1$ and $r_2$. Their surface temperatures are $T_1$ and $T_2$. If they radiate the same power,then $\frac{r_2}{r_1}$ is:

In the $MKS$ system,Stefan's constant is denoted by $\sigma$. In the $CGS$ system,the multiplying factor of $\sigma$ will be:

The temperature of a body is increased from $27\,^{\circ}C$ to $127\,^{\circ}C$. The radiation emitted by it increases by a factor of:

$A$ black body,at a temperature of $227\,^{\circ}C$,radiates heat at a rate of $7\,cal\,cm^{-2}\,s^{-1}$. At a temperature of $727\,^{\circ}C$,the rate of heat radiated in the same units will be:

$A$ black body emits energy at the rate of $1.0 \times 10^{6} \ J/s \cdot m^{2}$ at $127^{\circ}C$. At what temperature will the energy emission rate be $16.0 \times 10^{6} \ J/s \cdot m^{2}$ in $^{\circ}C$?

Parallel rays of light of intensity $I = 912 \ W m^{-2}$ are incident on a spherical black body kept in surroundings of temperature $T_0 = 300 \ K$. Take Stefan-Boltzmann constant $\sigma = 5.7 \times 10^{-8} \ W m^{-2} K^{-4}$ and assume that the energy exchange with the surroundings is only through radiation. The final steady state temperature of the black body is close to: (in $K$)