$A$ black body at a temperature of $127^{\circ}C$ radiates heat at the rate of $1 \ cal/cm^2 \cdot s$. At a temperature of $527^{\circ}C$,the rate of heat radiation from the body in $cal/cm^2 \cdot s$ will be:

When the temperature of a black body is increased, the value of $\lambda_m$ changes from $0.26 \mu m$ to $0.13 \mu m$. What is the ratio of its emissive power corresponding to these temperatures?

$A$ rectangular block of surface area $A$ emits energy $E$ per second at $27^{\circ} C$. If length and breadth are reduced to half of their initial values and the temperature is raised to $327^{\circ} C$,then the energy emitted per second becomes:

Two spheres of the same material have radii $1 \; m$ and $4 \; m$ and temperatures $4000 \; K$ and $2000 \; K$ respectively. The ratio of the energy radiated per second by the first sphere to that by the second is

$A$ black metal foil is kept at a distance $d$ from a circular heater. The power absorbed by the foil is $P$. If the temperature of the heater and the distance are both doubled,the power absorbed by the foil will be ..... $P$.

$A$ sphere and a cube,both made of copper,have equal volumes and are black. They are allowed to cool at the same temperature and in the same atmosphere. The ratio of their rate of loss of heat is: