- #1
En Joy
- 16
- 0
Confusion about Rayleigh-Jeans law
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Discussion Overview
The discussion revolves around the Rayleigh-Jeans law, specifically addressing confusion regarding different expressions for spectral density and their units. Participants explore the implications of using frequency versus wavelength in these expressions.
Discussion Character
- Debate/contested
Main Points Raised
- Some participants question whether the expressions are taken from different texts, suggesting that differing units may be a source of confusion.
- Others propose that the presence of an additional lambda in the denominator of one formula indicates a need to clarify whether spectral density is being referred to in terms of frequency (##u_\nu##) or wavelength (##u_\lambda##).
- There is a query regarding the exponent of wavelength, with one participant suggesting it should be (wavelength) ^3 instead of (wavelength) ^4 to maintain dimensional consistency.
- One participant corrects a previous claim, indicating that the first expression should use ν in the subscript instead of λ.
- Some participants emphasize that comparing spectral densities per unit wavelength and per unit frequency involves different units, which could lead to misunderstandings.
Areas of Agreement / Disagreement
Participants express differing views on the correct interpretation of the expressions and their units, indicating that multiple competing perspectives remain without a clear consensus.
Contextual Notes
Limitations include potential missing assumptions regarding the definitions of spectral density and the context in which the expressions are used. The discussion does not resolve the mathematical steps or the implications of the differing units.
- #2
Jilang
- 1,116
- 72
Are you taking these expressions from two different texts? They may be using different units.
- #3
soarce
- 154
- 24
In the second formula you have an additional lambda in the denominator. Maybe one should refer to spectral density in terms of frequency of in terms of wavelength, i.e. ##u_\nu## and ##u_\lambda##.
- #4
fireflies
- 210
- 13
Why (wavelength) ^4?
Shouldn't it be (wavelength) ^3??
Then dimensions are same
Shouldn't it be (wavelength) ^3??
Then dimensions are same
- #5
En Joy
- 16
- 0
No they are in same page of a book !Jilang said:
- #6
En Joy
- 16
- 0
Sorry guys, in the first expression this should be ν in the sub script instead of λ.En Joy said:
- #7
Jilang
- 1,116
- 72
Ah. Then you are not comparing apples with apples! One is the density per unit wavelength and one is per unit frequency. They would not be expected to have the same units. They are different things.
- #8
En Joy
- 16
- 0
Thank youJilang said:
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