Two electric lamps $A$ and $B$ radiate the same power. Their filaments have the same dimensions and have emissivities $e_A$ and $e_B$. Their surface temperatures are $T_A$ and $T_B$. The ratio $\frac{T_A}{T_B}$ will be equal to :-

The temperature of a spherical black body is inversely proportional to its radius. If its radius is doubled,then the power radiating from it will be

The radiant energy from the sun incident normally at the surface of the earth is $20 \, kcal/(m^2 \cdot min)$. What would have been the radiant energy incident normally on the earth,if the sun had a temperature twice of the present one? (in $kcal/(m^2 \cdot min)$)

If the ambient temperature is $300 \ K$,the rate of cooling at $600 \ K$ is $H$. In the same surroundings,the rate of cooling at $900 \ K$ is:

Calculate the radiation power for a sphere whose temperature is $227^{\circ} C$,radius is $2\, m$,and emissivity is $0.8$ (in $W$).

The total energy of a black body radiation source is collected for five minutes and used to heat water. The temperature of the water increases from $10.0^{\circ} C$ to $11.0^{\circ} C$. The absolute temperature of the black body is doubled and its surface area halved and the experiment repeated for the same time. Which of the following statements would be most nearly correct?