- #1
En Joy
- 16
- 0
In summary, the expressions being compared are from the same page of a book, but are not directly comparable as they represent density per unit wavelength and density per unit frequency, which are different units. The discrepancy in the use of lambda and nu in the subscripts is also noted.
- #2
Jilang
- 1,116
- 72
Are you taking these expressions from two different texts? They may be using different units.
- #3
soarce
- 155
- 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
- 12
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:
Related to Confusion about Rayleigh-Jeans law
1. What is the Rayleigh-Jeans law?
The Rayleigh-Jeans law is a theoretical law in physics that describes the energy distribution of blackbody radiation at different wavelengths. It was proposed by Lord Rayleigh and Sir James Jeans in the late 19th and early 20th century, but was later found to be inaccurate in certain cases and was superseded by the Planck's law of blackbody radiation.
2. What is the difference between the Rayleigh-Jeans law and the Planck's law?
The main difference between the two laws is that the Rayleigh-Jeans law predicts that the energy of blackbody radiation increases indefinitely with decreasing wavelength, while the Planck's law takes into account the quantization of energy, resulting in a different energy distribution at shorter wavelengths.
3. Why is the Rayleigh-Jeans law no longer considered accurate?
The Rayleigh-Jeans law was based on classical physics and did not take into account the quantization of energy that is observed at the atomic and subatomic level. This led to inaccuracies in certain cases, such as the ultraviolet catastrophe, where the law predicted infinite energy at short wavelengths.
4. What are some practical applications of the Rayleigh-Jeans law?
The Rayleigh-Jeans law is still used in certain fields of physics, such as astrophysics and cosmology, to understand the energy distribution of blackbody radiation in the universe. It has also been used in the development of technologies such as microwave ovens and infrared cameras.
5. Can the Rayleigh-Jeans law be modified to make it more accurate?
Yes, there have been attempts to modify the Rayleigh-Jeans law to make it more accurate, such as the Wien approximation which takes into account the high-frequency behavior of blackbody radiation. However, it was ultimately Planck's law that provided a more complete and accurate description of blackbody radiation.
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