$A$ black body radiates energy at the rate of $E \text{ W/m}^2$ at a high temperature $T \text{ K}$. When the temperature is reduced to $\left(\frac{T}{2}\right) \text{ K}$,the radiant energy is

If the temperature of the sun is doubled,the rate of energy received by the earth will be increased by a factor of:

Spheres $P$ and $Q$ are uniformly constructed from the same material,which is a good conductor of heat,and the radius of $Q$ is thrice the radius of $P$. The rate of fall of temperature of $P$ is $x$ times that of $Q$ when both are at the same surface temperature. The value of $x$ is:

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:

If the ratio of the radii of two spheres of the same material and at the same temperature is $1:2$,find the ratio of their emissive power.

$A$ black body at temperature $127^{\circ} C$ radiates heat at the rate of $5 \ cal / cm^2 \ s$. At a temperature $927^{\circ} C$,its rate of emission in units of $cal / cm^2 \ s$ will be