Joseph von Fraunhofer

Joseph von Fraunhofer was born on March 6, 1887 in Straubing, Bavaria. He was the youngest of eleven children of a poor glazier. As soon as he was of age, he began an apprenticeship under his father. His mother died when he was ten and his father when he was eleven, leaving him an orphan. Leaving his home he became the apprentice of Philipp Anton Weichelsberger, the court mirror and glass maker. Weicheslberger was a harsh master and did not allow young Fraunhofer time to study and read.

In 1801 the building that Fraunhofer and Weicheslberger were working in collapsed and both were rescued alive. The future king, Maximilliam Joseph IV was among the rescuers and helped the young man out giving him some money and appointing Joseph von Utzschneider to oversee his apprenticeship, allowing Fraunhofer books and study time. Fraunhofer tired of his apprenticeship and after writing Utzschnider he was offered a position at the Optical Institute at Benediktbeuern, this was a Benedictine monastery that had been converted into a research institute. Fraunhofer worked there, inventing ways to make the world's finest optical glass, surpassing the glass made in England. In 1818 he became the director of the institute.

In 1814 Franhofer invented the spectroscope allowing him to observe the spectral lines of the sun. Fraunhofer measured 574 dark lines in the sun's spectrum. Although these lines had been discovered earlier by William Hyde Wallaston, they are now known as Fraunhofer lines. Fraunhofer used his spectroscope to examine the emission spectrum of many elements and saw that they each had a unique spectrum. Fraunhofer also invented the diffraction grating, a series of thin lines on a lens, that causes a light source to be dispersed into its spectrum.

The dark lines Fraunhofer observed in the sun's spectrum are caused by the light absorbed by the outer layer of the sun. The chemical elements in the outer, cooler layer of the sun absorb certain wavelengths producing these dark lines in the sun's spectrum. Different stars, with different chemical elements in their atmospheres have different dark lines in their spectrums. The spectrum of the moon and the other planets in our solar system have similar dark lines to the sun's spectrum, because the light coming from them is the light of the sun reflected off of them.

Honors won by Fraunhofer include membership in the Bavarian Academy of Science and an honorary doctorate from the University of Erlangen. He is considered the founder of the German optical industry. He was knighted in 1824.

He died of tuberculosis on June 7, 1826.


References:

Kennelly, Colan; "Joseph Von Fraunhofer"; at.u.arizona.edu

"Joseph von Fraunhofer" at pioneers in optics (micro.magnet.fsu.edu)

Joseph von Fraunhofer Wikipedia Entry