Work

Experiments conducted in the late 19th century on cathode rays (radiation emitted when a voltage is applied between two metal plates in a glass tube filled with low-pressure gas) led to the discovery of electrons and X-rays. In crucial experiments performed by Philipp Lenard beginning in 1893, the glass tube was fitted with a thin aluminum window, making it possible to study the radiation outside the tube and thereby prove that it was not electromagnetic in nature.