Emissivity of radiation from a surface, Leslies cube

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Homework Help Overview

The discussion revolves around the emissivity of thermal radiation from different surfaces using Leslie's cube as a demonstration tool. The original poster seeks to understand why black surfaces emit more radiation compared to silver surfaces, referencing concepts of black body radiation.

Discussion Character

  • Exploratory, Conceptual clarification

Approaches and Questions Raised

  • Participants discuss the relationship between absorption and emission, noting that good absorbers are also good emitters. Questions arise regarding the physical explanation for the differences in emissivity between black and silver surfaces.

Discussion Status

The conversation is ongoing, with some participants providing insights into the principles of emissivity and reflection. However, there is a lack of consensus on the deeper physical explanations, and further exploration of the advantages and disadvantages of using Leslie's cube in practical situations is also being sought.

Contextual Notes

Participants are navigating the complexities of emissivity and its implications in real-life applications, while also considering the limitations of their experimental setup with Leslie's cube.

rayman123
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Homework Statement



Hello! I am going to do a demonstration involving the Leslie's cube to demonstrate the emissivity of a thermal radiation from different surfaces. I have been reading some about black body radiation which has emissivity = 1 but this is not the case. Leslie's cube has 4 surfaces but could someone explain to me why the black surface emitts the most of the radiation and the silver one least?

Thank you!



Homework Equations





The Attempt at a Solution


 
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Black surfaces absorb, silver or white surfaces reflect.

The absorption and emission processes are symmetrical. This means a good absorber is a ready emitter.

For the white or silvet surface pretend the energy to be emitted is just inside the cube. The silver surface will reflect the energy back into the box, so low emissivity.
 
yes I know that but I would like to know what is the physical explanaition for it? what makes that the black one emitts the most? why it has the highest emissivity ?
 
i just did experiment on Leslie's cube, but can not often answer 1 question: which says, what is the advantage and disadvantage of my device in every day life situation. can someone please help me with this!
 

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