Obtain the equation rate of emission of heat for perfect black body by using Stefan Boltzmaan law.

Obtain the equation rate of emission of heat for perfect black body by

1.	Obtain the equation rate of emission of heat for perfect black body by using Stefan Boltzmaan law.
Answer» SOLUTION :If Q is the amount of RADIANT energy from substance in time .t. and IRON cross-sectional area .A., then, `[P=W/t]` `W=Q/(At)""`[Power H, radiant energy Q] `:.Q=AWt` `(dQ)/(dt)AW` `=AesigmaT^(4)" "[because" From equation (1)"]` Now `T=T_(1)` at temp. `Q=Q_(1)`, `(dQ_(1))/(dt)=AsigmaeT_(1)^(4)` and `T=T_(2)` at temp. `Q=Q_(2)`, `(dQ_(2))/(dt)=AsigmaeT_(2)^(4)` Here, `T_(1)gtT_(2)` by taking `(dQ_(1))/(dt)gt(dQ_(2))/(dt)` `:.` By keeping substance of temp. `T_(1)` in surroundings to temp. `T_(2)`, rate of emission of energy, `(dQ)/(dt)=(dQ_(1))/(dt)-(dQ_(2))/(dt)` `=AsigmaeT_(1)^(4)-AsigmaeT_(2)^(4)` `=Asigmae(T_(1)^(4)-T_(2)^(2))` If `T_(1)=T` and `T_(2)=T_(S)`, `(dQ)/(dt)=Asigmae(T^(4)-T_(S)^(4))" where "(TgtT_(S))`