I Why is Planck radiation the most radiation a body can emit?

1. Mar 29, 2016

Julia Coggins

Why is Planck radiation the greatest amount of radiation that any body at thermal equilibrium can emit from its surface, whatever its chemical composition or surface structure?

2. Mar 29, 2016

Simon Bridge

The clue is in the definition... what would it mean if the body could emit more?
What would happen?

3. Mar 30, 2016

Julia Coggins

So that's an inherent fact? Planck radiation depends on the temperature of the body, so for example at room temperature a body emits infared radiation and cannot be seen. Whereas at the surface of the sun, it emits visible light as well. I guess Planck radiation is inherently the limit, but refering to it when in fact in radiates another light by means of Plack confuses me.

4. Apr 1, 2016

Simon Bridge

The definition of plank radiation is not "the inherent limit of radiation"... it's a bit more complicated than that and it arises as a consequence of other things. However: if a body radiated beyond the plank limit, then that would be a contradiction in terms ... so say the body is emitting radiation that can be found by the plank-limit equation ... we can ask, how is it that this is the limit? What mechanism says "no more"?