Understanding Stefan's Law for Students in Class 11

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Discussion Overview

The discussion revolves around Stefan's Law, particularly its implications and applications in thermodynamics as understood by students in class 11. Participants seek to clarify the law's principles and address specific scenarios related to energy radiation and emissivity.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant states that Stefan's Law indicates the energy radiated per unit area per unit time by a black body is proportional to the absolute temperature raised to the fourth power.
  • Another participant questions whether a body surrounded by a higher temperature would still radiate energy, suggesting it might contradict thermodynamic laws.
  • A response clarifies that the body would still radiate heat, but would experience a net heat gain due to the surrounding temperature.
  • Concerns are raised about why only the emissivity of the object is considered in Stefan's Law, with one participant suggesting that the surrounding's emissivity is not accounted for because the object is radiating heat to its surroundings.
  • It is mentioned that the amount of radiation reaching another object is influenced by a factor known as "view factor."

Areas of Agreement / Disagreement

Participants express differing views on the implications of Stefan's Law in specific scenarios, particularly regarding the effects of surrounding temperatures and the role of emissivity. The discussion remains unresolved with multiple competing perspectives.

Contextual Notes

Some assumptions about thermodynamic principles and definitions of emissivity are not fully explored, leaving room for further clarification and discussion.

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?
 
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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?
 
asdofindia said:
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.
 
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?
 
Last edited:
GT1 said:
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".
 

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