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Ludwig Zehnder c. 1930
Ludwig Louis Albert Zehnder (4 May 1854 in Illnau – 24 March 1949 in Oberhofen am Thunersee) was a Swiss physicist, one of the inventors of the Mach–Zehnder interferometer.
Zehnder was a student of Wilhelm Röntgen, professor of physics at the universities of Freiburg and Basle. He produced the first pictures of the human skeleton by shining x-rays through the human body.