Lenard ray

== English == === Etymology === Named after the German physicist Philipp Lenard, who first described them. === Noun === Lenard ray (plural Lenard rays) (dated) One of the rays that emanate from the outer surface of a plate composed of any material permeable by cathode rays, such as aluminium, which forms a portion of a wall of a vacuum tube, or which is mounted within the tube and exposed to radiation from the cathode. ==== Related terms ==== Lenard tube