Philipp Lenard investigated cathode rays by allowing them to leave a discharge tube through a thin window. Studying their effects beyond the original discharge made their penetration, absorption and ability to ionize other material experimentally accessible. These measurements helped separate the properties of the rays from the particular gas discharge that generated them. His lecture describes the apparatus and the comparison of different materials, connecting an invisible beam with measurable fluorescence and electrical effects.[ref]
On Cathode Rays by Philipp Lenard. 1906 Nobel lecture, window apparatus and material-dependent effects
A physicist.[ref]
https://www.uni-heidelberg.de/en/university/history/heidelberg-university-nobel-laureates?menu=2. Independent biographical identity and professional specialization
Portrait of Philipp Lenard
. Photographer unidentified; AIP Emilio Segrè Visual Archives, via Encyclopaedia Britannica, as recorded on Commons. Commons claims expiry for an anonymous work under its European anonymous-work public-domain rationale., via Wikimedia Commons. Source. Articles by others on the same topic
Philipp Lenard (1862–1947) was a German physicist known for his work in experimental physics, particularly in the fields of cathode rays and photoelectric effect. He was awarded the Nobel Prize in Physics in 1905 for his investigations into the properties of cathode rays, which were among the first experiments to explore the behavior of electrons. Lenard's research contributed to the understanding of the nature of light and radiation.