Parallel rays of light of intensity $\mathrm{I}=912{\mathrm{Wm}}^{-2}$ are incident on a spherical black body kept in surroundings of temperature $300 \mathrm{K}$ Take Stefan-Boltzmann constant $\mathrm{\sigma }=5.7\times {10}^{-8}{\mathrm{Wm}}^{-2}{\mathrm{K}}^{-4}$ and assume that the energy exchange with the surrounding is only through radiation. The final steady state temperature of the black body is close to:

A red-glass piece is heated until it glows in dark. The colour of the glow will be:

The intensity of radiation emitted by the sun has its maximum value at a wavelength of $510 \mathrm{nm}$ and that emitted by the north star has the maximum value at $350 \mathrm{nm}$. If these stars behave like black bodies then the ratio of the surface temperature of the sun and the north star is

A black body emits radiations of maximum intensity at $5000 \stackrel{\circ }{\mathrm{A}}$ when its temperature is $1227°\mathrm{C}$. If, its temperature is increased by $1000°\mathrm{C}$  then the maximum intensity of emitted radiation will be at:

The temperature of furnace is $1420 ° C$ and intensity is maximum in its radiation spectrum at $4800 A°$ If the intensity of a star is maximum near $1200 A°$ then the temperature of the surface of star is 

Three very large plates of same area are kept parallel and close to each other. They are considered as ideal black surfaces and have very high thermal conductivity. The first and third plates are maintained at temperatures 2T and 3T respectively. The temperature of the middle (i.e. second) plate under steady state condition is

If a piece of metal is heated to temperature θ and then allowed to cool in a room which is at temperature $T_0$ the graph between the temperature T of the metal and time $t$ will be closed to: