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kritika saxena Grade: 12

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??

9 years ago

Answers : (1)

askIITIians Expert
21 Points

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


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.

9 years ago
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