My textbook says that net rate of heat transfer due to radiation is εσA(T^4-To^4)$\epsilon \sigma A(T^4-T_o^4)$ but i couldn't understand it.
Rate of emission is εσAT^4$\epsilon \sigma A T^4$ and rate of absorption is aσATo^4$a \sigma A T_o^4$ so net rate of heat transfer must be εσAT^4-aσATo^4$\epsilon \sigma A T^4 - a \sigma A T_o^4$,it is possible only if a=e$a=e$ which means body is in thermal equilbriumequilibrium.
But that is not always the case.please Please help.
