Find the rate of energy radiated per minute by an incandescent lamp at $2000 \ K$. The surface area is $5 \times 10^{-5} \ m^{2}$,the emissivity is $0.85$,and $\sigma = 5.7 \times 10^{-8} \ W \ m^{-2} \ K^{-4}$. (in $J$)

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

$A$ solid copper sphere (density $\rho$ and specific heat capacity $c$) of radius $r$ at an initial temperature $200 \, K$ is suspended inside a chamber whose walls are at almost $0 \, K$. The time required (in $\mu s$) for the temperature of the sphere to drop to $100 \, K$ is:

The amount of heat energy radiated by a metal at temperature $T$ is $E$. When the temperature is increased to $3T$,the energy radiated is: (in $E$)

$A$ black body is heated from $27^oC$ to $127^oC$. The ratio of their energies of radiations emitted 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 ...