Correct Answer - Option 4 : 81
Concept:
Stefan-Boltzmann Law
The thermal energy radiated by a black body per second per unit area is proportional to the fourth power of the absolute temperature and is given by:
E ∝ T4
E = σT4
σ = The Stefan – Boltzmann constant = 5.67 × 10-8 W m-2K-4
Calculation:
Given:
T1 = 400 K, T2 = 1200 K
\(\frac{{{E_2}}}{{{E_1}}} = {\left( {\frac{{{T_2}}}{{{T_1}}}} \right)^4} = {\left( {\frac{{1200}}{{400}}} \right)^4} =3^4 = 81\)