The rate of emission of radiation of a black body at $273^o C$ is $E$, then the rate of emission of radiation of this body at $0^o C$ will be

The spectrum of a black body at two temperature  $27\,^oC$ and $327\,^oC$ is shown in the figure. Let  $A_1$ and $A_2$ be the areas under the two curves respectively. The value of $\frac {A_2}{A_1}$ is

Assuming newton's law of cooling to be valid, body at temperature $50^o\ C$ in surrounding of temperature $20^o\ C$ , achieve steady state with help of $100\ W$ heater. If same body has temperature $35^o\ C$ in same surrounding, then power of heater required to maintain steady state  ........ $W$

Two rods are connected as shown. The rods are of same length and same cross sectional area. In steady state, the  temperature $\left( \theta  \right)$ of the interface will be........ $^oC$

In a composite rod, when two rods of different lengths and of the same area are joined end to end. If $K$ is the coefficient of thermal conductivity of composite rod, then $\left( {\frac{{{\ell _1} + {\ell _2}}}{K}} \right)$ is equal to

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