Is Plancks function a distribution one?

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Discussion Overview

The discussion revolves around whether Planck's law or function can be classified as a true distribution function, particularly in comparison to the Maxwell-Boltzmann distribution. Participants explore the definitions and characteristics of these functions, focusing on normalization and the implications for their classification.

Discussion Character

  • Debate/contested

Main Points Raised

  • Some participants note that Planck's law is often referred to as a distribution but question whether it qualifies as a true distribution function since its integral does not equal 1.
  • Others argue that Planck's law is normalized to total power per unit area, which differentiates it from a probability distribution.
  • A participant highlights that while Planck's function can be considered a distribution, it does not represent a probability density function due to its specific form related to radiance.
  • Another participant acknowledges the distinction and agrees that Planck's function should be treated as a distribution, attributing the non-normalization to the factors involved in calculating irradiance and radiance.

Areas of Agreement / Disagreement

Participants express differing views on whether Planck's law constitutes a true distribution function, with some agreeing on its classification as a distribution while others emphasize its differences from probability distributions. The discussion remains unresolved regarding the classification criteria.

Contextual Notes

There are limitations in the discussion regarding the definitions of distribution functions and the specific normalization conditions applied to Planck's law compared to other distributions.

epik
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In many textbooks Plancks law or function is also referred to as Plancks distribution.
But is it a true distribution function?

I was reading a textbook where it was describing Maxwell-Boltzmann distribution
(which is a true distribution function since its integral across the range equals 1 )
and a few pages later it was comparing it with Plancks distribution pointing out how similar they look.

But is Plancks law a true distribution function?
 
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Usually Planck's law is defined so that it is normalized to total power per unit area, rather than 1, which would have made it a probability distribution. But if you ignore the probability definition, it is a distribution.
 
mathman said:
Usually Planck's law is defined so that it is normalized to total power per unit area, rather than 1, which would have made it a probability distribution. But if you ignore the probability definition, it is a distribution.

But the form of the Plancks function that gives radiance (Energy/time/area/steradian/wavelength or frequency) is not a probability density function,right?
 
mathman said:
Usually Planck's law is defined so that it is normalized to total power per unit area, rather than 1, which would have made it a probability distribution. But if you ignore the probability definition, it is a distribution.

Ok,I got what you said.It is a distribution and should be treated as one.The reason its integral is not 1 is because it is multiplied by a factor to give irradiance, radiance etc.

Thanks.
 

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