Ernst Karl Abbe

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**Ernst Abbe**
Ernst Karl Abbe (1840-1905)
Born	January 23, 1840 Eisenach, Saxe-Weimar-Eisenach
Died	January 14, 1905 Jena, Germany
Residence	Germany
Nationality	German
Field	Physicist
Institution	University of Jena
Alma mater	University of Göttingen University of Jena
Academic advisor	Wilhelm Weber Carl Snell
Notable students	Heinrich Friedrich Weber
Known for	Abbe number

Ernst Karl Abbe (January 23, 1840 in Eisenach – January 14, 1905 in Jena), was a German physicist. He was a professor at the University of Jena.

Abbe is best known for his work in optics. He designed the first refractometer. He discovered the Abbe number, a measure of any transparent material's variation of refractive index with wavelength. Already a professor in Jena, he was hired by Carl Zeiss to improve the manufacturing process of optical instruments, which back then was largely based on trial and error. In a long and fruitful collaboration, Abbe created the mathematical foundation of microscope design, which became essential for the later preeminent position of the Zeiss company. In particular, he discovered the Abbe sine condition, a breakthrough in lens design. He also invented the Abbe condenser, used for microscope illumination.^[1] During his association with Carl Zeiss' microscope works he also introduced the eight-hour workday, in remembrance of the 14-hour workday of his own father.