You can tell what the highest frequency of radiation an object will emit

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Discussion Overview

The discussion revolves around the interpretation of Wien's law in relation to the highest frequency of radiation emitted by an object based on its temperature. Participants explore the implications of temperature on radiation frequency, intensity, and the behavior of black bodies in isolation.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants assert that Wien's law indicates the peak frequency of radiation emitted by an object based on its temperature.
  • There is a discussion about whether the term "power" should be replaced with "intensity" when describing radiation, with some agreeing that intensity is a clearer term.
  • One participant notes that as the temperature decreases, the intensity of radiation emitted by the human body decreases, suggesting that it would not emit frequencies lower than infrared before reaching critical temperatures.
  • A later reply introduces a scenario involving a black body isolated in space, arguing that in this case, it is possible to discuss the highest frequency emitted, as emitting a photon of a certain frequency would lead to the body's temperature approaching absolute zero.

Areas of Agreement / Disagreement

Participants generally agree on the interpretation of Wien's law regarding peak frequency, but there is contention regarding the terminology of "power" versus "intensity." Additionally, the discussion about the highest frequency emitted by a black body introduces competing views that remain unresolved.

Contextual Notes

Some assumptions about the definitions of intensity and power, as well as the implications of temperature on radiation, are not fully explored. The scenario involving a black body raises questions about the conditions under which the highest frequency can be emitted.

LogicalAcid
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By its temperature? I just want to know if I understand Wien's law right.
 
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No, Wien's law tells you the peak frequency---i.e. the frequency at which the most power is radiated, based on temperature.
 
zhermes said:
No, Wien's law tells you the peak frequency---i.e. the frequency at which the most power is radiated, based on temperature.

I concur that the answer is no. However should your word "power" be changed by "intensity"?
 
fluidistic said:
I concur that the answer is no. However should your word "power" be changed by "intensity"?
Yes, that would probably be a more clear way of phrasing it. However, the intensity is the power per unit solid-angle, frequency and area.
 
zhermes said:
Yes, that would probably be a more clear way of phrasing it. However, the intensity is the power per unit solid-angle, frequency and area.

So basically, when we get colder and colder, our body in general having less kinetic energy, will start radiating lower intensity infrared. But we will never emit anything lower than infrared, we'd freeze to death many times over first right?
 
Correct... note that the human body only has the range of a few degrees in which it can operate. Thus the range in peak-intensity of radiation would be minute.
 
zhermes said:
Correct... note that the human body only has the range of a few degrees in which it can operate. Thus the range in peak-intensity of radiation would be minute.

Exactly, thank you!
 
Let me add a comment. Suppose we are using a black body whose temperature is T at time t0 but after that it is isolated in empty space. In this situation it makes sense to talk about the highest frequency it can emit, for there is a photon whose frequency is such that, if the body emits it, its temperature will fall to zero kelvin. No highest frequency can be emited.
I am particularly not considering rest mass energy here.

Best wishes

DaTario
 

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