When the temperature of a solid surface changes from 227°C to 1227°C, its total emissive power changes from E1 to E2. The ratio $E_2/E_1$ will be
- A. 3
- B. 9
- C. 81
- D. Cannot be determined
Answer: C. 81
Explanation: $E \propto T^4$. $T_1 = 227+273=500 K$. $T_2 = 1227+273=1500 K$. $E_2/E_1 = (1500/500)^4 = 3^4 = 81$.