A spherical black body with a radius of 12 cm radiates 450 watt power at 500 K. If the radius were halved and the temperature doubled, the power radiated in watt would be :

1800 225 450 1000

1800

Rate of power loss : r ∝ R2T4 \(\frac{r_1}{r_2} = \frac{R_1^2T_1^2}{R_2^2T_2^2} \) \(\frac{450}{r_2} = 4 × \frac{1}{16} \) \(r_2\) = 1800 W