Two identical metal balls at temperatures $200^{\circ}C$ and $400^{\circ}C$ are kept in air at $27^{\circ}C$. The ratio of net heat loss by these bodies is:

Two spherical bodies of radii $r_1$ and $r_2$ have surface temperatures $T_1$ and $T_2$ respectively. They radiate the same power. The ratio $r_1/r_2$ is . . . . . .

Two spheres made of the same material have radii in the ratio $1 : 2$. If both are at the same temperature,what is the ratio of the energy emitted per second by them?

Two spherical black bodies of radii $R_1$ and $R_2$ and with surface temperatures $T_1$ and $T_2$ respectively radiate the same power. The ratio of $R_1$ to $R_2$ will be

$A$ black body emits energy at the rate of $1 \ cal/cm^2 \cdot s$ at a temperature of $127^{\circ}C$. Find the rate of energy emission at a temperature of $527^{\circ}C$ in $cal/cm^2 \cdot s$.

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 $K$)