Physics - Heat & Thermo Question with Solution | TestHub

When the centre of earth is at a distance of $1.5\times 10^{11}\mathrm{m}$ from the centre of sun, the intensity of solar radiation reaching at the earth's surface is $1.26\mathrm{kW}/{\mathrm{m}}^2$. There is a spherical cloud of cosmic dust, containing iron particles. The melting point for iron particles in the cloud is 2000 K. Find the distance of iron particles from the centre of sun at which the iron particle starts melting. (Assume sun and cloud as a black body, $\sigma =5.6\times 10^{-8}\mathrm{W}/{\mathrm{m}}^2{\mathrm{K}}^4$ )