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Can you please explain in detail about stephens law and about the emmissivites..?? how a radiation occur when a black body is inside a core(hollow sphere) at certain temp??
Stefan's Law STEFAN’S LAW => It states that the total amount of energy radiated per second per unit area of a perfect black body is directly proportional to the fourth power of the absolute temperature of the surface of the body i.e. E ∝ T4 Or, E = σ T4 Where σ is the Stefan’s constant. Its value is 5.67 x 10-8 Js-1 m-2 K-4 in SI. In case, the perfect black body at temperature T is placed in an enclosure at temperature T0, then heat energy radiated per second per unit area is given by E = σ (T4 – T04 ) In case, T ≥ T0 then above equation reduces to E = e σ (T4 – T04) Where e is called the radiation emissivity of the surface. Its value depends upon nature of surface.
Stefan's Law
STEFAN’S LAW => It states that the total amount of energy radiated per second per unit area of a perfect black body is directly proportional to the fourth power of the absolute temperature of the surface of the body i.e.
E ∝ T4
Or,
E = σ T4
Where σ is the Stefan’s constant. Its value is 5.67 x 10-8 Js-1 m-2 K-4 in SI.
In case, the perfect black body at temperature T is placed in an enclosure at temperature T0, then heat energy radiated per second per unit area is given by
E = σ (T4 – T04 )
In case, T ≥ T0 then above equation reduces to
E = e σ (T4 – T04)
Where e is called the radiation emissivity of the surface. Its value depends upon nature of surface.
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