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I Discovery of how to measure wavelength absorption lines

  1. May 7, 2016 #1
    who was the first person to discover how to measure the wavelength of
    absorption lines in the solar or stellar spectra and what method was used?
  2. jcsd
  3. May 7, 2016 #2

    Simon Bridge

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  4. May 10, 2016 #3
    I understand that Fraunhofer's measured wavelengths of spectral lines and that he had scribed a diffraction granting with 50000 grooves per inch and had used it for that purpose, getting results for the sodium doublet close to modern values. Regarding his procedure, was he the first or was it Augusti Fresnel or someone else? And what unit did they use?

    In 1801 Thomas Young used his experiments with double slits to measure wavelengths of the seven rainbow 'colours' described by Newton and got respectable results. Still don't know the units though.
  5. May 10, 2016 #4


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    did you actually read the Wiki link given to you ?
    it answered your Q

    there is no mention of Augusti Fresnel being involved with emission/absorption lines discovery either in that link or in the wiki entry for Augusti Fresnel

  6. May 10, 2016 #5
    Yes I did read the link. No need to be rude. This is a debate/discussion in one of my classes, and the question is generate thought beyond Wiki. Just because Wiki doesn't mention it, doesn't mean those people mentioned didn't do what was said.
  7. May 11, 2016 #6


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    wasn't being rude :smile:

    your response hinted that you didn't read the link or do any further study
    that last bit which is particularly encouraged here on PF

    The wiki link told you the name of the person that first noticed the dark bands in the spectrum
    but you didn't bother to mention that name, rather went on to other names that weren't in the link
  8. May 11, 2016 #7

    Simon Bridge

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    This is vital information you left out.

    It's odd to find that you are asked to go beyond wikipedia for a question that is completely answered within wikipedia ...
    The questions were:
    Johannas Fraunhofer
    diffraction spectroscopy

    Further questions were:
    Fraunhofer was first. Since you read the link, you ready the bit right at the start that said:
    In 1814, Fraunhofer independently rediscovered the lines and began a systematic study and careful measurement of the wavelength of these features.
    ... under "Discovery". I suppose it does not actually state in so many words that Frounhofer was first, but it also does not put any others before him.
    You can use this information to refine your googling to confirm the result if you want to be absolutely sure.
    You can also look up the references wikipedia supplies for this information or use the titles as clues for further google searches:
    1. Hearnshaw, J.B. (1986). The analysis of starlight. Cambridge: Cambridge University Press. p. 27. ISBN 0-521-39916-5.
    2. Joseph Fraunhofer (1814 - 1815) "Bestimmung des Brechungs- und des Farben-Zerstreuungs - Vermögens verschiedener Glasarten, in Bezug auf die Vervollkommnung achromatischer Fernröhre" (Determination of the refractive and color-dispersing power of different types of glass, in relation to the improvement of achromatic telescopes), Denkschriften der Königlichen Akademie der Wissenschaften zu München (Memoirs of the Royal Academy of Sciences in Munich), 5: 193-226; see especially pages 202-205 and the plate following page 226.
    From the sounds of things - this is what the exercise is all about. "Going beyond wiki" does not usually mean "ask someone else".... rather you should do your own research. We can point you in the right direction but you have to to the work yourself.

    The inch.

    Also inches ... Young developed the technique of diffraction spectroscopy used by Fresnel and others ... Fresnel has nothing to do with the question in post #1.

    But if you want to be sure, you can use google to look for references to these people making wavelength measurements of the dark lines in the solar spectrum.
    What sort of search term could you use?[/quote][/quote]
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