Cathode rays are streams of electrons observed in discharge tubes. If an evacuated glass tube is equipped with two electrodes and a voltage is applied, glass behind the positive electrode is observed to glow, due to electrons emitted from the cathode, they were first observed in 1869 by German physicist Julius Plücker and Johann Wilhelm Hittorf, were named in 1876 by Eugen Goldstein Kathodenstrahlen, or cathode rays. In 1897, British physicist J. J. Thomson showed that cathode rays were composed of a unknown negatively charged particle, named the electron. Cathode ray tubes use a focused beam of electrons deflected by electric or magnetic fields to render an image on a screen. Cathode rays are so named because they are emitted by the negative electrode, or cathode, in a vacuum tube. To release electrons into the tube, they first must be detached from the atoms of the cathode. In the early cold cathode vacuum tubes, called Crookes tubes, this was done by using a high electrical potential of thousands of volts between the anode and the cathode to ionize the residual gas atoms in the tube.
The positive ions were accelerated by the electric field toward the cathode, when they collided with it they knocked electrons out of its surface. Modern vacuum tubes use thermionic emission, in which the cathode is made of a thin wire filament, heated by a separate electric current passing through it; the increased random heat motion of the filament knocks electrons out of the surface of the filament, into the evacuated space of the tube. Since the electrons have a negative charge, they are repelled by the negative cathode and attracted to the positive anode, they travel in straight lines through the empty tube. The voltage applied between the electrodes accelerates these low mass particles to high velocities. Cathode rays are invisible, but their presence was first detected in early vacuum tubes when they struck the glass wall of the tube, exciting the atoms of the glass and causing them to emit light, a glow called fluorescence. Researchers noticed that objects placed in the tube in front of the cathode could cast a shadow on the glowing wall, realized that something must be travelling in straight lines from the cathode.
After the electrons reach the anode, they travel through the anode wire to the power supply and back to the cathode, so cathode rays carry electric current through the tube. The current in a beam of cathode rays through a vacuum tube can be controlled by passing it through a metal screen of wires between cathode and anode, to which a small negative voltage is applied; the electric field of the wires deflects some of the electrons, preventing them from reaching the anode. The amount of current that gets through to the anode depends on the voltage on the grid. Thus, a small voltage on the grid can be made to control a much larger voltage on the anode; this is the principle used in vacuum tubes to amplify electrical signals. The triode vacuum tube developed between 1907 and 1914 was the first electronic device that could amplify, is still used in some applications such as radio transmitters. High speed beams of cathode rays can be steered and manipulated by electric fields created by additional metal plates in the tube to which voltage is applied, or magnetic fields created by coils of wire.
These are used in cathode ray tubes, found in televisions and computer monitors, in electron microscopes. After the 1654 invention of the vacuum pump by Otto von Guericke, physicists began to experiment with passing high voltage electricity through rarefied air. In 1705, it was noted that electrostatic generator sparks travel a longer distance through low pressure air than through atmospheric pressure air. In 1838, Michael Faraday applied a high voltage between two metal electrodes at either end of a glass tube, evacuated of air, noticed a strange light arc with its beginning at the cathode and its end at the anode. In 1857, German physicist and glassblower Heinrich Geissler sucked more air out with an improved pump, to a pressure of around 10−3 atm and found that, instead of an arc, a glow filled the tube; the voltage applied between the two electrodes of the tubes, generated by an induction coil, was anywhere between a few kilovolts and 100 kV. These were called Geissler tubes, similar to today's neon signs.
The explanation of these effects was that the high voltage accelerated free electrons and electrically charged atoms present in the air of the tube. At low pressure, there was enough space between the gas atoms that the electrons could accelerate to high enough speeds that when they struck an atom they knocked electrons off of it, creating more positive ions and free electrons, which went on to create more ions and electrons in a chain reaction, known as a glow discharge; the positive ions were attracted to the cathode and when they struck it knocked more electrons out of it, which were attracted toward the anode. Thus the ionized air was electrically conductive and an electric current flowed through the tube. Geissler tubes had enough air in them that the electrons could only travel a tiny distance before colliding with an atom; the electrons in these tubes moved in a slow diffusion process, never gaining much speed, so these tubes didn't produce cathode rays. Instead, they produced a colorful glow discharge, caused when the electrons struck gas atoms, exciting their orbital electrons to higher energy levels.
The electrons released this energy as light. This process is called fluorescence. By the 1870s, British physicist William Crookes and others were
The Restless Stranger is the first album by American Music Club, released in 1985. All songs written by Mark Eitzel. Tracks 13-15 are bonus tracks on the CD reissue. "Room Above the Club" - 3:50 "$1,000,000 Song" - 3:56 "Away Down the Street" - 4:21 "Yvonne Gets Dumped" - 3:16 "Mr. Lucky" - 2:42 "Point of Desire" - 4:32 "Goodbye Reprise #54" - 3:54 "Tell Yourself" - 4:03 "When Your Love Is Gone" - 4:19 "Heavenly Smile" - 1:58 "Broken Glass" - 4:23 "Hold on to Your Love" - 2:21 "Restless Stranger" - 4:04 "How Low? " - 4:23 "I'm in Heaven Now" - 3:51 Mark Eitzel - vocals Dan Pearson - bass Vudi - guitar Matt Norelli - drums Brad Johnson - Keyboards Bobby Neel Adams - photography
Keena Ruth Rothhammer is an American former competition swimmer, Olympic champion, former world record-holder in two events. Rothhammer was born in Little Rock, is Jewish; as a teenager, she grew up in Santa Clara and trained with the Santa Clara Swim Club in Santa Clara under the coach George Haines, noted for leading U. S. Olympic swimmers during the 1970s; as a 15-year-old, Rothhammer represented the United States at the 1972 Summer Olympics in Munich, Germany. She won the gold medal in the women's 800-meter freestyle and set a new world record in the event twice, on successive days, she won the bronze medal in the women's 200-meter freestyle at the 1972 Olympics. At the 1973 World Aquatics Championships, she won the 200-meter freestyle and finished second in the 400-meter freestyle; the same year, she was named North American Athlete of the Year. She was inducted into the International Swimming Hall of Fame as an "Honor Swimmer" in 1991. List of Olympic medalists in swimming List of select Jewish swimmers List of University of Southern California people List of World Aquatics Championships medalists in swimming World record progression 400 metres freestyle World record progression 800 metres freestyle Keena Rothhammer – Jews in Sports profile