If the temperature of the sun (black body) is doubled,the rate of energy received on earth will be increased by a factor of

$A$ solid sphere at a temperature $T \ K$ is cut into two hemispheres. The ratio of energies radiated by one hemisphere to the whole sphere per second is

State and explain the Stefan-Boltzmann law.

If a substance at temperature $T$ is kept in surroundings at temperature $T_S$,what is the net rate of loss of radiation energy?

$Assertion :$ Bodies radiate heat at all temperatures.
$Reason :$ Rate of radiation of heat is proportional to the fourth power of absolute temperature.

At temperature $T$,the power radiated by a body is $Q$ watts. At the temperature $3T$,the power radiated by it will be (in $Q$)