"cathode ray." YourDictionary, n.d. Web. 25 May 2018. <http://www.yourdictionary.com/cathode-ray>.
cathode ray. (n.d.). Retrieved May 25th, 2018, from http://www.yourdictionary.com/cathode-ray
(plural cathode rays)
In the early part of the 20th century, it was the first name given to electron beams emitted from a negatively charged cathode in a vacuum tube. The term has been used ever since. See CRT.