The unit of Stefan-Boltzmann's constant $(\sigma)$ is:

$A$ black body of surface area $10 \ cm^2$ is heated to $127^{\circ}C$ and is suspended in a room at temperature $27^{\circ}C$. The initial rate of loss of heat from the body at the room temperature will be ...... $W$.

The unit of Stefan's constant $\sigma$ is

Two spheres of same material and radii $5 \ m$ and $2 \ m$ are at temperatures $200 \ K$ and $250 \ K$ respectively. The ratio of energies radiated by them per second is

If the temperature of a black body increases from $7\,^{\circ}C$ to $287\,^{\circ}C$,then the rate of energy radiation increases by

If the temperature of a perfectly black body is reduced from $T$ to $T/2$,find the percentage decrease in the rate of emission.