The temperature of a body is $400^{\circ}C$. Assume the temperature of the surroundings is negligible. At what temperature will the body emit double the energy?

Which of the following graphs correctly represents the relation between $\ln E$ and $\ln T$, where $E$ is the amount of radiation emitted per unit time from unit area of a body and $T$ is the absolute temperature?

The Sun emits electromagnetic energy at a rate of $3.9 \times 10^{25} \ W$. Its radius is $6.96 \times 10^8 \ m$. The intensity of sunlight at the solar surface in $W \ m^{-2}$ is:

Two spheres made of the same material have radii in the ratio $1:2$. Both are at the same temperature. The ratio of heat radiation energy emitted per second by them is:

Calculate the radiation power for a sphere whose temperature is $227^{\circ} C$,radius is $2\, m$,and emissivity is $0.8$ (in $W$).

Two spheres of the same material have radii $1 \ m$ and $4 \ m$ and temperatures $4000 \ K$ and $2000 \ K$ respectively. The energy radiated per second by the first sphere is