$A$ 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

If the temperature of a body is increased from $-73^{\circ}C$ to $327^{\circ}C$,the ratio of its emissive power will be ...

The total radiant energy per unit area,normal to the direction of incidence,received at a distance $R$ from the centre of a star of radius $r$,whose outer surface radiates as a black body at a temperature $T \ K$ is given by

The unit of Stefan's constant is:

The actual temperature of a black body is $727^{\circ}C$. At what temperature in $K$ will the black body emit twice the radiation?

$A$ solid copper sphere of density $\rho$,specific heat capacity $C$ and radius $r$ is initially at $200 \ K$. It is suspended inside a chamber whose walls are at $0 \ K$. The time required (in $\mu s$) for the temperature of the sphere to drop to $100 \ K$ is ( $\sigma$ is Stefan's constant and all the quantities are in $SI$ units.)