Philipp Lenard

Philipp Lenard (1862–1947) was a German experimental physicist who investigated cathode rays and the photoelectric effect. He received the 1905 Nobel Prize in Physics for work on cathode rays.

Heinrich Hertz: A German physicist whose experiments demonstrated electromagnetic waves and investigated the photoelectric effect. Hertz’s observation that ultraviolet light helped discharge charged bodies prompted Lenard’s photoelectric experiments.
Cathode ray: A stream of electrons emitted from a cathode in a vacuum tube. Lenard’s Nobel-recognized experiments investigated the properties of these electron streams.
University of Heidelberg: A public research university in Heidelberg, Germany, founded in 1386. Lenard studied and later held a professorship at this university.
1905 Nobel Prize in Physics: The Nobel Prize in Physics awarded to Philipp Lenard for work on cathode rays. This award marked the international recognition of Lenard’s experimental program.
Albert Einstein: A German-born theoretical physicist who explained the photoelectric effect using light quanta. Einstein used Lenard’s measurements to develop a theory Lenard later rejected.
Lenard window: A thin metal foil that lets cathode rays pass from a vacuum tube into air. This device let Lenard examine cathode rays outside the discharge tube.
University of Bonn: A public research university in Bonn, Germany, founded in 1818. Lenard completed doctoral work in physics at Bonn under Heinrich Hertz.
Nazi physics: A political movement in Nazi Germany that promoted a racialized rejection of modern theoretical physics. Lenard became one of its leading advocates, attacking relativity and quantum theory as ‘Jewish physics.’
Wilhelm Röntgen: A German physicist who discovered X-rays in 1895 and received the first Nobel Prize in Physics. Lenard’s cathode-ray research helped establish the experimental setting for Röntgen’s discovery.
Photoelectric effect: The emission of electrons from matter after it absorbs electromagnetic radiation. Lenard measured how light frequency and intensity affected emitted electrons.

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