Discovery of how to measure wavelength absorption lines

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Discussion Overview

The discussion revolves around the historical discovery of how to measure the wavelength of absorption lines in solar or stellar spectra, focusing on the contributions of various scientists, particularly Johannas Fraunhofer and Thomas Young. Participants explore the methods used and the timeline of these discoveries, as well as the significance of different figures in this context.

Discussion Character

  • Debate/contested
  • Historical

Main Points Raised

  • Some participants assert that Johannas Fraunhofer was the first to measure the wavelengths of spectral lines using diffraction spectroscopy.
  • Others mention Thomas Young's experiments with double slits in 1801, which measured wavelengths of colors in the spectrum, but there is uncertainty about the units used.
  • There is a debate about whether Augusti Fresnel played a role in the discovery of absorption lines, with some participants arguing that he was not mentioned in relevant sources.
  • One participant emphasizes the importance of going beyond Wikipedia for deeper understanding, suggesting that the information provided in the link does not encompass all relevant historical contributions.
  • Participants discuss the specific method used by Fraunhofer, noting the use of a diffraction grating with 50,000 grooves per inch to achieve results close to modern values.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the contributions of different scientists, particularly regarding the roles of Fraunhofer and Fresnel. The discussion remains unresolved with multiple competing views on the historical context and significance of the discoveries.

Contextual Notes

There are limitations regarding the completeness of historical accounts, as some participants express uncertainty about the units used in early measurements and the specific contributions of various scientists. The discussion highlights the need for further research and clarification on these points.

Ava_Seven
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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?
 
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Simon Bridge said:
Have you tried entering "discovery of solar absorption lines" into google?
https://en.wikipedia.org/wiki/Fraunhofer_lines

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.
 
Ava_Seven said:
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?

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

D
 
davenn said:
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

D
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.
 
Ava_Seven said:
Yes I did read the link. No need to be rude.

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
 
Ava_Seven said:
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.
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:
who was the first person to discover how to measure the wavelength of
absorption lines in the solar or stellar spectra...
Johannas Fraunhofer
.. and what method was used?
diffraction spectroscopy

Further questions were:
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?
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.

And what unit did they use?
The inch.

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.
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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