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Information about Cathode Ray



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.

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 composed 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.

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.

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 of which they would pump the air out. 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.

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.

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 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. Relativistic electron beams can also serve as a gain medium for free electron lasers.

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.

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Electron

Theoretical estimates of the electron density for the first few hydrogen atom electron orbitals shown as cross-sections with color-coded probability density
Composition: Elementary particle
Family: Fermion
Group: Lepton
Generation: First
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vacuum tube, electron tube (inside North America), thermionic valve, or just valve (elsewhere); is a device used to amplify, switch, otherwise modify, or create an electrical signal by controlling the movement of electrons in a low-pressure space, often not
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A vacuum is a volume of space that is essentially empty of matter, such that its gaseous pressure is much less than standard atmospheric pressure. The Latin term in vacuo is used to describe an object as being in what would otherwise be a vacuum.
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An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte or a vacuum). The word was coined by the scientist Michael Faraday from the Greek words elektron
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A cathode is an electrode through which (positive) electric current flows out of a polarized electrical device. Mnemonic: CCD (Cathode Current Departs). To dispel a common misconception, often incorrectly inferred from the correct fact that in all electrochemical
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An anode is an electrode through which (positive) electric current flows into a polarized electrical device. Mnemonic: ACE (Anode Current Enters).
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diode is a component that restricts the directional flow of charge carriers. Essentially, a diode allows an electric current to flow in one direction, but blocks it in the opposite direction. Thus, the diode can be thought of as an electronic version of a check valve.
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Phosphorescence is a specific type of photoluminescence related to fluorescence. Unlike fluorescence, a phosphorescent material does not immediately re-emit the radiation it absorbs.
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list of sources of light, including both natural and artificial sources, and both processes and devices.

This is an incomplete list. Please add to this list if you are aware of an omission.
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vacuum pump is a pump that removes gas molecules from a sealed volume in order to leave behind a partial vacuum. The vacuum pump was invented in 1650 by Otto von Guericke.

Types

Pumps can be broadly categorized according to three techniques:[1]

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Otto von Guericke (originally spelled Gericke) [ˈgeːʁɪkə] (November 20, 1602 – May 11, 1686 (Julian calendar); November 30, 1602 – May 21, 1686 (Gregorian calendar) was a
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Michael Faraday

Michael Faraday, portrait by Thomas Phillips c1841-1842[2]
Born September 22 1791(1791--)
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An anode is an electrode through which (positive) electric current flows into a polarized electrical device. Mnemonic: ACE (Anode Current Enters).
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Voltage (sometimes also called electric potential difference or electrical tension) is the potential similarity of electrical potential between two points of an electrical or electronic circuit, expressed in volts.
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Johann Heinrich Wilhelm Geißler (May 26 1814 - January 24 1879) was a German physicist and inventor of the Geissler tube, a low pressure gas-discharge tube made of glass. He worked in his parent's business and worked later in different German universities.
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The Geissler tube is a glass tube for demonstrating the principles of electrical discharge. The tube was invented by the German physicist and glassblower Heinrich Geissler in 1857. The Geissler tube was an evacuated glass cylinder with an electrode at each end.
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Sir William Crookes

English chemist and physicist
Born 17 May 1832(1832--)
London, England
Died 4 March 1919 (aged 88)
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The Crookes tube is an evacuated glass cone with 3 node elements (one anode and two cathodes). It is an invention of the 19th century scientist William Crookes and is an evolutionary development of the earlier Geissler tube.
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For the periodical, see .
The 19th Century (also written XIX century) lasted from 1801 through 1900 in the Gregorian calendar. It is often referred to as the "1800s.
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This page is currently protected from editing until disputes have been resolved.
Protection is not an endorsement of the current [ version] ([ protection log]).
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Philipp Lenard

Philipp Lenard in 1905
Born May 7 1862(1862--)
Pressburg, Hungary
Died May 20 1947 (aged 86)
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Electron

Theoretical estimates of the electron density for the first few hydrogen atom electron orbitals shown as cross-sections with color-coded probability density
Composition: Elementary particle
Family: Fermion
Group: Lepton
Generation: First
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Flavour in particle physics
 

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electric field. This electric field exerts a force on other electrically charged objects. The concept of electric field was introduced by Michael Faraday.

The electric field is a vector field with SI units of newtons per coulomb (N C−1
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magnetic field is a field that permeates space and which exerts a magnetic force on moving electric charges and magnetic dipoles. Magnetic fields surround electric currents, magnetic dipoles, and changing electric fields.
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high voltage characterizes electrical circuits, in which the voltage used is the cause of particular safety concerns and insulation requirements. High voltage is used in electrical power distribution, in cathode ray tubes, to generate X-rays and particle beams, to demonstrate
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1. Electron guns 2. Electron beams 3. Focusing coils 4. Deflection coils 5. Anode connection 6. Mask for separating beams for red, green, and blue part of displayed image 7.
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18th century - 19th century - 20th century
1860s  1870s  1880s  - 1890s -  1900s  1910s  1920s
1894 1895 1896 - 1897 - 1898 1899 1900

:
Subjects:     Archaeology - Architecture -
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Karl Ferdinand Braun

Ferdinand Braun
Born May 6 1850(1850--)
Fulda, Hesse-Kassel, Germany
Died March 20 1918 (aged 69)
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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

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