The plots of intensity versus wavelength for three black bodies at temperature $T_1$, $T_2$ and $T_3$ respectively are as shown. Their temperatures are such that

Six identical conducting rods are joined as shown in figure. Points $A$ and $D$ are maintained at temperature of $200^o C$ and $20^o C$ respectively. The temperature of junction $B$ will be  ....... $^oC$ 

Two bodies $P$ and $Q$ have thermal emissivities of $\varepsilon_P$ and $\varepsilon_Q$ respectively. Surface areas of these bodies are same and the total radiant power is also emitted at the same rate. If temperature of $P$ is $\theta_P$ kelvin then temperature of $Q$ i.e. $\theta_Q$ is

A cylinder of radius $R$ made of a material of thermal conductivity $K_1$ is surrounded by a cylindrical shell of inner radius $R$ and outer radius $2R$ made of material of thermal conductivity $K_2.$ The two ends of the combined system are maintained at two different temperatures. There is no loss of heat across the cylindrical surface and the system is in steady state. The effective thermal conductivity of the system is

A heated body emits radiation which has maximum intensity at frequency $f_m$. If the temperature of the body is doubled

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