Cathode_Ray_Tubes

Cathode Ray Tubes The first cathode ray tube was successfully invented by William Crookes. Crookes, an English chemist, passed an electric current through a tube containing air at low pressure (1). Before Crookes though, Micheal Faraday tried to pass an electric current through a tube, but was unsuccessful. The vacuum Faraday had was not strong enough for his voltage. Tubes with better vacuum than Faraday had at the time were available in Crookes time. Crookes was able to confirm the existence of cathode rays by displaying them, with his invention of the Crookes tube, a crude prototype for all future Cathode ray tubes (2). The way the cathode ray tube works is that the tube has metal electrodes inside it where it’s connected to a vacuum pump, and most of the air is removed (1). A beam of current is seen as a green fluorescence, observed when the beam strikes a screen coated with zinc sulfide (1). When that happens the beam is attracted to the anode in the tube. The cathode ray tube was built mainly to prove the existence of cathode rays. Not only did it help to prove the existence of cathode rays, but it also led to other scientific discoveries by other scientists. For example, Joseph John Thomson’s experiment involving cathode ray tubes showed that cathode rays were deflected in an electric field and that the beam was attracted to the positive plate and repelled by the negative plate (1). He also proved that cathode rays consisted of negatively charged particles and that the particles were the alike despite the materials from where the electrodes were made or the kind of gas that was in the tube. Thomson then named the negatively charged particles electrons. Since, Thomson measured the amount the negatively charged particles bounced back he was able to determine the mass ratio of electrons. Today, there is plenty of technology that has been generated from the cathode ray tube. For instance, computers, television sets, monitors, and video cameras are just a few items that have come from cathode ray tubes. A lot of Crookes tubes stood at the base of further discoveries like the X-ray tube (3). Also, there have been improvements towards the cathode ray tube. There are tubes that can use multiple beams of electrons to present millions of colors. Crookes invention of the cathode ray tube, ultimately lead to the understanding of how electrons behave and work. That is why Crookes is considered by many as the father of cathode ray tubes. Bibliography 1. Hill, W. J., and Kolb, K. D. “Chemistry for Changing Times.” Upper Saddle River, NJ: Pearson Education, Inc., 2004, 2001, 1998 2. Bellis, Mary. “Highlights of CRT history.” The history of the Cathode Ray Tube. 2005. Accessed March 8, 2005 http://investors.about.com/library/investors/blcathoderaytube.htm 3. Regards, Henk. “Crookes Tube.” The Cathode Ray Tube Site, old electronic glassware. 2004-2005. Accessed March 8, 2005 http://members.chello.nl/h.dijkstra19/page7.htm