Parallel rays of light of intensity I = 912   W m - 2 are incident on a spherical black body kept in…

Parallel rays of light of intensity I=912 Wm-2 are incident on a spherical black body kept in surroundings of temperature 300 K. Take Stefan-Boltzmann constant σ=5.7×10-8 Wm-2 K-4 and assume that the energy exchange with the surroundings is only through radiation. The final steady state temperature of the black body is close to
  1. 330 K
  2. 660 K
  3. 990 K
  4. 1550 K

Solution

Rate of radiation energy lost by the sphere = Rate of radiation energy incident on it
⇒σ×4πr2T4-3004=912×πr2
⇒T=11×102≈330 K

Asked in: JEE Advanced 2014 (Paper 2)

Practice more Kinetic Theory of Gases and Radiation questions on Aicharya