A schematic diagram of a Crookes tube apparatus. A is a low voltage power supply to heat cathode C (a "cold cathode" was used by Crookes). B is a high voltage power supply to energize the phosphor-coated anode P. Shadow mask M is connected to the cathode potential and its image is seen on the phosphor as a non-glowing area.

Cathode rays are streams of electrons observed in vacuum tubes, i.e. evacuated glass tubes that are equipped with at least two electrodes, a cathode (negative electrode) and an anode (positive electrode) in a configuration known as a diode. Image File history File links CrookesTube. ... Image File history File links CrookesTube. ... The Crookes tube is an evacuated glass cone with 3 node elements (one anode and two cathodes). ... e- redirects here. ... Structure of a vacuum tube diode Structure of a vacuum tube triode In electronics, a vacuum tube, electron tube, or (outside North America) thermionic valve or just valve, is a device used to amplify, switch or modify a signal by controlling the movement of electrons in an evacuated space. ... Look up Vacuum in Wiktionary, the free dictionary. ... An electrode is an electrical conductor used to make contact with a metallic part of a circuit (e. ... Diagram of a copper cathode in a Daniells cell. ... Diagram of a zinc anode in a galvanic cell. ... Types of diodes. ...

When the cathode is heated, it emits radiation which travels to the anode. If the inner glass walls behind the anode are coated with a phosphorescent material, they glow. A metal shape placed between the electrodes casts a shadow on the glowing coating. This suggests that the cause of the light emission was comprised of rays emitted by the cathode and hitting the coating. They travel towards the anode in straight lines and continue past it for some distance. Phosphorescent powder under visible light, ultraviolet light, and total darkness. ... This page is a list of sources of light. ...

History

After the 1650 invention of the vacuum pump by Otto von Guericke, physicists began to experiment with mixtures of rarefied air and electricity. In 1705, it was noted that electrostatic generator sparks travel a longer distance in rarefied air than in standard air. In 1838, Michael Faraday passed current through a rarefied air filled glass tube and noticed a strange light arc with its beginning at the anode (positive electrode) and its end almost at the cathode (negative electrode). The only place where there was no luminescence was just in front of the cathode, which came to be called the "cathode dark space", "Faraday dark space" or "Crookes dark space". Hence, it became known that whenever a voltage is applied to rarefied air, light is produced. The Roots blower is one example of a vacuum pump A vacuum pump is a pump that removes gas molecules from a sealed volume in order to leave behind a partial vacuum. ... Otto von Guericke Otto von Guericke (originally spelled Gericke) [] (November 20, 1602 – May 11, 1686 (Julian calendar); November 30, 1602 – May 21, 1686 (Gregorian calendar)) was a German scientist, inventor, and politician. ... Michael Faraday, FRS (September 22, 1791 – August 25, 1867) was an English chemist and physicist (or natural philosopher, in the terminology of that time) who contributed significantly to the fields of electromagnetism and electrochemistry. ... Diagram of a zinc anode in a galvanic cell. ... International safety symbol Caution, risk of electric shock (ISO 3864), colloquially known as high voltage symbol. ...

Scientists began traveling from town-to-town delighting audiences by making light glow in glass tubes. They did this by first taking an air-filled glass tube which they would pump the air out of; next wires would be attached at the opposite ends of the tube, and then the voltage would be turned up. This would make the tube glow in lovely patterns. In 1857, German physicist and Glass blower Heinrich Geissler sucked even more air out with an improved pump and noticed a fluorescent glow, thus inventing the Geissler tube. While Geissler tubes are intended to cause an enclosed low pressure gas to glow, observers noticed that certain glasses used in the tube envelope (enclosure) would glow, but only at the end connected to the positive side of the power supply. Special tubes were developed for the study of these rays by William Crookes and are called Crookes tubes. Heinrich Geissler (May 26, 1814 - January 24, 1879) was a German physicist. ... The Geissler tube is a glass tube for demonstrating the principles of electrical discharge. ... Sir William Crookes, OM, FRS (17 June 1832 – 4 April 1919) was an English chemist and physicist. ... The Crookes tube is an evacuated glass cone with 3 node elements (one anode and two cathodes). ...

Toward the end of the 19th century, this phenomenon was studied in great detail by physicists, yielding a Nobel Prize, for example, to Philipp von Lenard. It was soon understood that cathode rays consist of the actual carriers of electricity which are now known as electrons. The fact that the cathode emits the rays showed that electrons have negative charge. Alternative meaning: Nineteenth Century (periodical) (18th century — 19th century — 20th century — more centuries) As a means of recording the passage of time, the 19th century was that century which lasted from 1801-1900 in the sense of the Gregorian calendar. ... Nobel Prize medal. ... Philipp Eduard Anton von Lenard (born in Bratislava on June 7, 1862 – died May 20, 1947 in Messelhausen) was a physicist and the winner of the Nobel Prize for Physics in 1905 for his research on cathode rays and the discovery of many of their properties. ... e- redirects here. ... Electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interaction. ...

Applications

Cathode rays propagate in a straight line in the absence of external influences, but are deflected by electric or magnetic fields (which can be produced by placing high-voltage electrodes or magnets outside the vacuum tube - this explains the effect of magnets on a TV screen). The refinement of this idea is the cathode ray tube (CRT), also known as Braun's tube (because it was invented 1897 by Ferdinand Braun). The CRT is key to television sets (though alternative display technologies are making inroads), oscilloscopes, and vidicon television cameras. In physics, the space surrounding an electric charge or in the presence of a time-varying magnetic field has a property called an electric field. ... Magnetic field lines shown by iron filings In physics, a magnetic field is a solenoidal vector field in the space surrounding moving electric charges, such as those in electric currents and bar magnets. ... In electrical engineering High voltage refers to a voltage which is high. ... Cathode ray tube employing electromagnetic focus and deflection Cutaway rendering of a color CRT Electron guns Electron beams Focusing coils Deflection coils Anode connection Mask for separating beams for red, green, and blue part of displayed image Phosphor layer with red, green, and blue zones Close-up of the phosphor... 1897 (MDCCCXCVII) was a common year starting on Friday (see link for calendar). ... Karl Ferdinand Braun (June 6, 1850 - April 20, 1918) was a German physicist, born in Fulda. ... Television set may refer to: Television, a device to display television programs Television studio, an installation in which television or video productions take place Set construction, theatrical scenery This is a disambiguation page: a list of articles associated with the same title. ... Illustration showing the interior of a cathode-ray tube for use in an oscilloscope. ... In older video cameras, prior to the 1990s, a video camera tube or pickup tube was used instead of a charge-coupled device (CCD). ...

In addition to their use within cathode ray tubes, higher energy beams of relativistic electrons (generated by various types of electron beam accelerators) are used extensively within many industries to perform precision electron beam welding, rapid curing of thermosetting plastics, and cross-linking of thermoplastics to improve their physical properties. Albert Einsteins theory of relativity is a set of two theories in physics: special relativity and general relativity. ... For the DC Comics Superhero also called Atom Smasher, see Albert Rothstein. ... Electron beam welding is a welding process where the energy to melt the material is applied by an electron beam. ... Thermosetting plastics (thermosets) refer to a range of polymer materials that cure, through the addition of energy, to a stronger form. ... Vulcanization is an example of cross-linking. ... A thermoplastic is a plastic that softens when heated and hardens again when cooled. ...

Recent developments in electron beam accelerator technology include compact modular KeV accelerators which are being adopted by consumer packaging, medical device sterilization, and air treatment applications. These devices produce far less x-ray radiation than MeV accelerators with housings that look like early microwave ovens as opposed to lead lined concrete bunkers. Kev can refer to either: A regional term for the chav social group in the United Kingdom An abbreviation - keV - of the unit Kiloelectronvolt An abbreviation for the given name Kevin. ... An electronvolt (symbol: eV) is the amount of energy gained by a single unbound electron when it falls through an electrostatic potential difference of one volt. ...

External links

• The Cathode Ray Tube site