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B Why did Max Planck quantize light?

  1. Apr 11, 2017 #1
    I've read up on the history of quantization and I can't seem to find a definitive answer on why Planck actually quantized light. Some sources say that he came up with the idea of energy being quantized in order to solve the blackbody problem, whilst others say that he was trying to create a more efficient light bulb. Which is it or is it both?

    Also, if he did quantize energy in the effort of trying to create a better light bulb, how does quantizing light help do that?
     
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  3. Apr 11, 2017 #2

    PeterDonis

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    Can you give a specific reference?
     
  4. Apr 11, 2017 #3
  5. Apr 11, 2017 #4

    PeterDonis

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  6. Apr 11, 2017 #5
    Thanks
     
  7. Apr 11, 2017 #6

    fresh_42

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    I consider this as a (not very popular) urban legend right away, if not to say simply wrong. It reads like a bad mixture of Planck's and Einstein's vita.
    E.g. from Wikipedia "The German Bureau for measures and weights was founded 1946 in the soviet occupied zone ..."
    "Founded in 1917 as the Normenausschuß der deutschen Industrie (NADI, "Standardisation Committee of German Industry"), the NADI was renamed Deutscher Normenausschuß (DNA, "German Standardisation Committee") in 1926 to reflect ..."

    Moreover, I doubt that the term "German" connected to light bulbs in the 1890's is very accurate. At this time Germany was about 20 years old and I doubt that their concerns were about energy efficiency of light bulbs.

    The black body radiation is the correct origin (1900). Planck started to consider heat radiation in the second half of the 1890's and the article claims the first half. In addition it's very unllikely that they had asked such a young person (~35) at the time and not, e.g. Helmholtz.
     
  8. Apr 11, 2017 #7

    PeterDonis

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  9. Apr 11, 2017 #8

    fresh_42

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    My major doubts come from what this "bureau of standards" should have been. And where this rather modern aspect of "saving a few dollars" should have arisen from. Both sounds as it wouldn't fit into the early 1890's. Maybe a small talk at some meeting became a rumor.

    Edit: What makes me even more suspicious is that on Google, a search engine that usually finds the absurdest combinations, only finds explanations for kids like "people wondered why light bulbs become yellow whereas iron becomes red" when searched for "Glühbirne+Planck". One would expect that such a legend would appear on German websites. It doesn't.
     
    Last edited: Apr 11, 2017
  10. Apr 12, 2017 #9

    DrClaude

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  11. Apr 12, 2017 #10

    vanhees71

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    I've not read the website, but it's true that the very accurate measurements of the black-body spectrum over a wide range of wave lengths were done by Rubens and Kurlbaum at the "Physikalisch technische Reichsanstalt" (then the "bureau of standards" in Germany) with the motivation to establish a standard for the upcoming light bulbs. One should note that Germany in 1880ies was booming in science and technology compared to the pretty low state (compared to e.g., Britain) before, and the Physikalisch Technische Reichsanstalt. The PTR was founded in 1887 by Werner von Siemens and Hermann von Helmholtz, who was also its first president. Planck was closely related to the researchers at the Reichsanstalt and got the data on the high-precision measurement of the black-body spectrum first hand. In this, pretty indirect sense, physics has to thank the need for standards in lightning technology for helping to discover quantum theory (in it's "old version").
     
  12. Apr 12, 2017 #11

    f95toli

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    It refers to PTB. See
    https://www.ptb.de/cms/en/about-us-careers/about-us/history-of-ptr-and-ptb.html

    Note that a lot of countries founded their NMIs at the end o the 1890s. PTB was first(?) but NIST was founded in 1901 and NPL (UK) was founded in 1902.
    This is all connected to the fact the first CGPM was held in Paris in 1889; i.e. the creation of a "proper" international system of units.
     
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