Understanding Stefan's Law for Students in Class 11

[Ayushi]

Hello i am a new member of this forum. I am a student of class 11th. I came across a new law , 'Stefan's law', in my class. I did not understand it much. Could any of you help me to understand it please?

 

[Kurdt]

It just states that the energy radiated per unit area per unit time by a black body is proportional to the absolute temperature raised to the fourth power.

http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/stefan.html

 

[asdofindia]

What if it is surrounded by something of a temperature higher than itself? Would it still radiate energy? Won't that be against thermodynamic laws?

 

[rock.freak667]

What if it is surrounded by something of a temperature higher than itself? Would it still radiate energy? Won't that be against thermodynamic laws?

It would still radiate heat, it is just that it would have a net heat gain.

 

[GT1]

Why does on Stefan's law only the emissivity of the object is used- why the emissivity of the surrounding is not taken into account?

 

[rock.freak667]

Why does on Stefan's law only the emissivity of the object is used- why the emissivity of the surrounding is not taken into account?

Because the object is radiating heat to the surroundings. So if the object it white, it will radiate less heat than if it were black.

How much radiation reaches another object depends on something called "view factor".