Josef Von Fraunhofer (1787-1826)   Solar Spectrum

 ( extended biography )
 Josef Von Fraunhofer was the eleventh and last child born to Franz Xaver Fraunhofer, a glass master worker, on March 6, 1787. His mother died when he was ten years old, and his father died a year later.  Since compulsory school attendance was not required in Bavaria before 1802, the young boy was sent as an apprentice to the glass master Weichselberger in Munich. Weichselberger was extremely demanding of the youth and Fraunhofer was forbidden by the glass master to attend the vacation schools ( 50 days of vacation  per year in Bavaria at the time). Of great importance to the development of Fraunhofer was a catastrophic collapse of the two buildings that Weichselberger had rented in Munich in July 1801. The boy was in the workshop at the time and buried in the ruble. A dramatic rescue brought him into contact with Count Maximilian IV ( later King Max I) and the entrepreneur Joseph Utzschneider. The Count gave the youth the modern equivalent of 40000DM($30000) and took him under his protection. In 1804 he used half of the money he had received from the Count to purchase the remainder of his apprenticeship from Weichselberger, and in 1806 Utzschneider brought him into his Optical Institute.

When Fraunhofer started working for Utzschneider he could scarcely perform the most simple arithmetic. Utzschneider purchased books on mathematics and optics for Fraunhofer, and the young man would study these as long as daylight allowed, or on his vacation days outside. He was largely self-taught. Fraunhofer was a significant addition to Utzschneider's company, inventing or perfecting industrial techniques.

Among Fraunhofer's achievements were the invention of the diffraction grating, a detailed study of the solar spectrum, and production of the finest telescopes available in his day.

Fraunhofer died on on June 7, 1826 after a year long bout with lung tuberculosis. His life was commemorated by a medal struck in his honor ( and Reichenbach) by King Ludwig I.  The epitaph placed on his grave stone by Utzschneider read " Approximavit sidera " , " He brought the stars closer to us."

 
Dramatic representation of Fraunhofer's rescue           Medallion struck in honor of
( A. Mueller, 1852)                                                       Fraunhofer and Reichenbach by
                                                                                    King Ludwig  I

Fraunhofer lines


 
 

Fraunhofer lines   
Dark lines in the absorption spectrum of solar radiation due to absorption by gases in the outer portions of the sun and in the earth's atmosphere.
Fraunhofer lines are designated by letters, as the K-line, or by wavelength, as the 4046-angstrom line of iron.
The major Fraunhofer lines are:
angstroms  Line due to 
7594  Telluric oxygen 
6867  Telluric oxygen 
6563  hydrogen, H 
D1  5896  sodium 
D2  5890  sodium 
D3  5876  helium 
5270  iron and calcium 
b1  5184  magnesium 
4861  hydrogen, H 
4308  iron (and calcium) 
3968  calcium 
3934  calcium