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Parallel light of intensity I = 912 W/m² falls on a spherical black body placed in surroundings at 300 K. With Stefan-Boltzmann constant sigma = 5.7e-8 W/m²/K⁴ and energy exchange only by radiation, find the body's final steady-state temperature (approximately).

1. 330 K
2. 660 K
3. 990 K
4. 1550 K

Correct answer: 330 K

Solution

Balancing absorbed solar plus surroundings against emission gives T⁴ = I/(4*sigma) + 300⁴, so T ~ 330 K.

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