b
\({\text{P}}\, \propto \,{\text{(}}{{\text{T}}^{\text{4}}} - T_0^4)\, \Rightarrow \,P\, \propto \,{T^4}\,\,\,\,(\because \,\,{T_0}\, <  < \,T)\) અને

\({\text{P}}\, \propto \,\frac{{\text{1}}}{{{{\text{d}}^{\text{2}}}}}\,\, \Rightarrow \,P\, \propto \,\frac{{{T^4}}}{{{d^2}}} \Rightarrow \,\frac{{{P_1}}}{{{P_2}}} = {\left( {\frac{{{T_1}}}{{{T_2}}}} \right)^4} \times {\left( {\frac{{{d_2}}}{{{d_1}}}} \right)^2}\)

\( \Rightarrow \,\frac{P}{{{P_2}}} = {\left( {\frac{T}{{2T}}} \right)^4} \times {\left( {\frac{{2d}}{d}} \right)^2} = \frac{1}{4} \Rightarrow \,{P_2} = 4P\)