AP EAMCET Engineering 2018 Apr 24 Shift 1 Paper

The expression of the power radiating from a black body is,
P=σAT4
P=σ(4πR2)(

k

R

)4 ( As, T∝

1

R

⇒T=

k

R

)
P∝

1

R2

From above expression, when radius is doubled, the radiating power of the sphere becomes one fourth.