A power source of power \( P \) is placed at centre of a spherical shell of radius \( R \). Temperature of surface of shell is \( T_{0} \). Now shell is covered by another shell of radius \( 2 R \), and as a result temperature of inner shell in steady state becomes \( T_{1} \). Considering all bodies to behave like a black body, then
(1) \( T_{0}=\left(\frac{P}{4 \pi R^{2} \sigma}\right)^{\frac{1}{4}} \)
(2) \( T_{0}=\frac{1}{2}\left(\frac{P}{4 \pi R^{2} \sigma}\right)^{\frac{1}{4}} \)
(3) \( I_{1}=\left(\frac{P}{2 \pi R^{2} \sigma}\right)^{\frac{1}{4}} \)
(4) \( T_{1}=\left(\frac{P}{\pi R^{2} \sigma}\right)^{\frac{1}{4}} \)