A problem about blackbody radiation

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Discussion Overview

The discussion revolves around the concept of blackbody radiation, specifically comparing the emission characteristics of black bodies and grey bodies. Participants explore the implications of the Stefan–Boltzmann law and seek to understand why grey bodies emit less radiation than black bodies at the same temperature.

Discussion Character

  • Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant states the Stefan–Boltzmann law for black bodies and introduces the modified equation for grey bodies, seeking an explanation for the difference in radiation emission.
  • Another participant questions the conditions that define a blackbody, specifically asking why a blackbody is considered "black."
  • A participant explains that a black body absorbs all incident electromagnetic waves, while a grey body absorbs only a portion and reflects the rest.
  • It is noted that a black body radiates energy at the same rate it absorbs it, whereas a grey body, absorbing less energy, has less energy available to radiate.

Areas of Agreement / Disagreement

Participants present varying perspectives on the definitions and characteristics of black and grey bodies, with some explanations aligning while others raise questions, indicating that the discussion remains unresolved.

Contextual Notes

Participants do not fully explore the underlying assumptions or definitions that might clarify the differences between black and grey bodies, leaving some aspects of the discussion open to interpretation.

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The Stefan–Boltzmann law :
J = kT^4 where k is Stefan–Boltzmann constant.

but for non black body ( or grey body)
the equ becomes
J = εkT^4
where 0<ε<1

can anyone explain y a grey body emit less radiation when compare to the black body at same T? It can found the ans in wiki or the reference book "modern physics"

thank you
 
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What is the condition it has to meet to be considered a blackbody? (Why is a blackbody "black"?)

Compare with grey.
 
Black body absorb all incident em wave while grey body absorbs a part of it and reflects the remains
 
Black-body also radiates at the same rate as it absorbs.
A grey body is just the same as a black-body but it absorbs less energy - therefore it has less energy to radiate.
 

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