Physics
Cathode Rays
Cathode rays are streams of electrons that are emitted from the negative electrode, or cathode, in a vacuum tube. They were first observed by British physicist J.J. Thomson in the late 19th century and played a crucial role in the discovery of the electron. Cathode rays are important in understanding the behavior of charged particles and have applications in various electronic devices.
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12 Key excerpts on "Cathode Rays"
- E. A. Davis, Isabel Falconer(Authors)
- 2002(Publication Date)
- CRC Press(Publisher)
vivid phosphorescence at the places where the deflected rays struck the screen. These non-deflected rays do not seem to exhibit any of the characteristics of Cathode Rays, and it seems possible that they are merely jets of uncharged %uminous gas shot out through the slit from the neighbourhood of the cathode by a kind of explosion when the discharge passes. L. The curves described by the Cathode Rays in a uniform magnetic 6eld are, very approximately at any rate, circular for a large part of their course ; this is the path which would be de~cribed if the Cathode Rays marked the path of negatively electrified particles projected with great velocities from the neighbourhood of the negative electrode. Indeed, all the effects produced by a magnet on these rays, and some of these are complicated, as, for example, when the rays are curled up into spirals under the action of a magnetic force, are in exact agree- ment with the consequences of this view. We can, moreover, show by direct experiment that a chwge of negative electricity folloss the course of the Cathode Rays. One way in which this has been done is by an experiment due to Perrin, the details of which are shown in the accompanying figure (Fig. 8.) In this experiment the rays are slloned to pass inside a metallic cylinder X-rays and Cathode Rays (1895-1900) 1897.1 OR Cathode Bays. 7 through a small hole, and the cylinder, when these rays enter it, gets a negative charge, while if the rays are deflected by a magnet, so as to escape the hole, the cylinder remains without charge. I t seems to me that to the experiment in this form it might be objected that, though the experiment shows that negatively electrified bodies are projected normally from the cathode, and are deflected by a magnet, it does not show that when the Cathode Rays are defleoted by a magnet the path of the electrified particles coincides with the path of the Cathode Rays.
eBook - PDFUnderstanding The Universe: From Quarks To The Cosmos
From Quarks to the Cosmos
- Donald Lincoln(Author)
- 2004(Publication Date)
- World Scientific(Publisher)
Crookes investigated the flow of electricity and determined that electricity (perhaps) was flowing from the plate connected to the negative side of the battery (this plate was called the cathode) towards the plate connected to the positive side of the battery (called the anode). Subsequently, in 1876, the German physicist Eugen Goldstein, a contemporary of Crookes whose most active research period was earlier, had named this flow “Cathode Rays.” Crookes tube (shown in Figure 2.1a) was modified by his contemporaries to better inspect their properties by putting a small hole in the plate connected 24 u n d e r s t a n d i n g t h e u n i v e r s e to the positive side of the battery. This hole allowed the Cathode Rays to pass through and hit the far end of the glass vessel. With this improvement on Crookes’ design, the study of Cathode Rays could begin in earnest. It was found that the Cathode Rays trav-eled in straight lines and could cause, by their impact on the end of t h e p a t h t o k n o w l e d g e 25 Figure 2.1 Diagrams of variants of Crookes’ tubes. the glass vessel, great heat. Crookes knew that earlier studies had proven that charged particles would move in a circle in the presence of a magnetic field. When Cathode Rays also were shown to be deflected in the presence of a magnetic field, Crookes concluded that Cathode Rays were a form of electricity. Using the improved version of the Crookes tube, one could coat the end of the glass vessel with a phosphorescent material like zinc sulfide and observe that Cathode Rays caused the zinc sulfide to glow. The astute reader will recognize in these early experiments the origin of their computer monitor or tel-evision, also called a CRT or cathode ray tube.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- White Word Publications(Publisher)
____________________ WORLD TECHNOLOGIES ____________________ electron is a combination of the word electric and the suffix -on , with the latter now used to designate a subatomic particle, such as a proton or neutron. Discovery A beam of electrons deflected in a circle by a magnetic field The German physicist Johann Wilhelm Hittorf undertook the study of electrical conductivity in rarefied gases. In 1869, he discovered a glow emitted from the cathode that increased in size with decrease in gas pressure. In 1876, the German physicist Eugen Goldstein showed that the rays from this glow cast a shadow, and he dubbed the rays Cathode Rays. During the 1870s, the English chemist and physicist Sir William Crookes developed the first cathode ray tube to have a high vacuum inside. He then showed that the luminescence rays appearing within the tube carried energy and moved from the cathode to the anode. Furthermore, by applying a magnetic field, he was able to deflect the rays, thereby demonstrating that the beam behaved as though it were negatively charged. In 1879, he proposed that these properties could be explained by what he termed 'radiant matter'. He suggested that this was a fourth state of matter, consisting of negatively charged molecules that were being projected with high velocity from the cathode. The German-born British physicist Arthur Schuster expanded upon Crookes' experiments by placing metal plates in parallel to the Cathode Rays and applying an electric potential between the plates. The field deflected the rays toward the positively charged plate, providing further evidence that the rays carried negative charge. By measuring the ____________________ WORLD TECHNOLOGIES ____________________ amount of deflection for a given level of current, in 1890 Schuster was able to estimate the charge-to-mass ratio of the ray components.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Academic Studio(Publisher)
Discovery A beam of electrons deflected in a circle by a magnetic field The German physicist Johann Wilhelm Hittorf undertook the study of electrical conductivity in rarefied gases. In 1869, he discovered a glow emitted from the cathode that increased in size with decrease in gas pressure. In 1876, the German physicist Eugen Goldstein showed that the rays from this glow cast a shadow, and he dubbed the rays Cathode Rays. During the 1870s, the English chemist and physicist Sir William Crookes developed the first cathode ray tube to have a high vacuum inside. He then showed that the luminescence rays appearing within the tube carried energy and moved from the cathode to the anode. Furthermore, by applying a magnetic field, he was able to deflect the rays, thereby demonstrating that the beam behaved as though it were negatively charged. In 1879, he proposed that these properties could be explained by what he termed 'radiant matter'. He suggested that this was a fourth state of matter, consisting of negatively charged molecules that were being projected with high velocity from the cathode. The German-born British physicist Arthur Schuster expanded upon Crookes' experiments by placing metal plates in parallel to the Cathode Rays and applying an electric potential between the plates. The field deflected the rays toward the positively charged plate, providing further evidence that the rays carried negative charge. By measuring the amount of deflection for a given level of current, in 1890 Schuster was able to estimate ________________________ WORLD TECHNOLOGIES ________________________ the charge-to-mass ratio of the ray components. However, this produced a value that was more than a thousand times greater than what was expected, so little credence was given to his calculations at the time. In 1896, the British physicist J. J. Thomson, with his colleagues John S.
eBook - PDFHalf-Hours with Great Scientists
The Story of Physics
- Charles G. Fraser(Author)
- 2019(Publication Date)
- University of Toronto Press(Publisher)
Therefore, there must be rays emanating from the cathode (fig. 323). Seven years later, Eugen Goldstein of Berlin very naturally named these Cathode Rays. ... a ., . . . , FIG. 323. Cathode Rays. Any solid or fluid, whether insulator or conductor, which is placed in front of the cathode, cuts off the glow. . . . No bendings out of the straight line occur. . . . We see most clearly the rectilinear transmission of the glow if it goes out from a point cathode, and through a great length of the tube, brings the surface of the glass to fluorescence. ... If in such conditions, any object is set in the space filled with the glow, it casts a sharp shadow on the fluorescing wall by cutting off from it the cone of rays, diverging from the cathode as origin. 3 Hittorf and Goldstein observed that a cathode ray is emitted in general at right angles to the surface which produces it. One special form of vacuum tube is called a Hittorf tube. 'Annalcn der Physik unà demie (1869), cxxvi, 1. 480 The Story of Electricity and Magnetism DEFLECTION BY MAGNET In much of his study of Cathode Rays Hittorf collaborated with his teacher, Julius Plücker (1801-68), also of Bonn. Pliicker showed that Cathode Rays are deflected by a magnetic field.* The credit for this impor-tant discovery is shared by Hittorf and Sir William Crookes, who in-vestigated the phenomenon in greater detail. At this time advances were taking place so rapidly that some priorities are disputed or shared by way of compromise. The sense of deflection of the Cathode Rays, Crookes found to be in accordance with Ampere's swimmer rule, so that a cathode ray behaves as though it were a wireless current. Plücker also invented a special form of vacuum tube called a Plücker tube. The central part of the tube is one or two millimetres in diameter. He used such tubes in making spectroscopic examination of the light produced with different gases in the tube. From these re-searches come the modern neon tube and its family of relatives.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Academic Studio(Publisher)
However, this produced a value that was ________________________ WORLD TECHNOLOGIES ________________________ more than a thousand times greater than what was expected, so little credence was given to his calculations at the time. In 1896, the British physicist J. J. Thomson, with his colleagues John S. Townsend and H. A. Wilson, performed experiments indicating that Cathode Rays really were unique particles, rather than waves, atoms or molecules as was believed earlier. Thomson made good estimates of both the charge e and the mass m , finding that cathode ray particles, which he called corpuscles, had perhaps one thousandth of the mass of the least massive ion known: hydrogen. He showed that their charge to mass ratio, e / m , was independent of cathode material. He further showed that the negatively charged particles produced by radioactive materials, by heated materials and by illuminated materials were universal. The name electron was again proposed for these particles by the Irish physicist George F. Fitzgerald, and the name has since gained universal acceptance. While studying naturally fluorescing minerals in 1896, the French physicist Henri Becquerel discovered that they emitted radiation without any exposure to an external energy source. These radioactive materials became the subject of much interest by scientists, including the New Zealand physicist Ernest Rutherford who discovered they emitted particles. He designated these particles alpha and beta, on the basis of their ability to penetrate matter. In 1900, Becquerel showed that the beta rays emitted by radium could be deflected by an electric field, and that their mass-to-charge ratio was the same as for Cathode Rays. This evidence strengthened the view that electrons existed as components of atoms. The electron's charge was more carefully measured by the American physicist Robert Millikan in his oil-drop experiment of 1909, the results of which he published in 1911.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Library Press(Publisher)
However, this produced a value that was ________________________ WORLD TECHNOLOGIES ________________________ more than a thousand times greater than what was expected, so little credence was given to his calculations at the time. In 1896, the British physicist J. J. Thomson, with his colleagues John S. Townsend and H. A. Wilson, performed experiments indicating that Cathode Rays really were unique particles, rather than waves, atoms or molecules as was believed earlier. Thomson made good estimates of both the charge e and the mass m , finding that cathode ray particles, which he called corpuscles, had perhaps one thousandth of the mass of the least massive ion known: hydrogen. He showed that their charge to mass ratio, e / m , was independent of cathode material. He further showed that the negatively charged particles produced by radioactive materials, by heated materials and by illuminated materials were universal. The name electron was again proposed for these particles by the Irish physicist George F. Fitzgerald, and the name has since gained universal acceptance. While studying naturally fluorescing minerals in 1896, the French physicist Henri Becquerel discovered that they emitted radiation without any exposure to an external energy source. These radioactive materials became the subject of much interest by scientists, including the New Zealand physicist Ernest Rutherford who discovered they emitted particles. He designated these particles alpha and beta, on the basis of their ability to penetrate matter. In 1900, Becquerel showed that the beta rays emitted by radium could be deflected by an electric field, and that their mass-to-charge ratio was the same as for Cathode Rays. This evidence strengthened the view that electrons existed as com-ponents of atoms. The electron's charge was more carefully measured by the American physicist Robert Millikan in his oil-drop experiment of 1909, the results of which he published in 1911.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- College Publishing House(Publisher)
However, this produced a value that was ____________________ WORLD TECHNOLOGIES ____________________ more than a thousand times greater than what was expected, so little credence was given to his calculations at the time. In 1896, the British physicist J. J. Thomson, with his colleagues John S. Townsend and H. A. Wilson, performed experiments indicating that Cathode Rays really were unique particles, rather than waves, atoms or molecules as was believed earlier. Thomson made good estimates of both the charge e and the mass m , finding that cathode ray particles, which he called corpuscles, had perhaps one thousandth of the mass of the least massive ion known: hydrogen. He showed that their charge to mass ratio, e / m , was independent of cathode material. He further showed that the negatively charged particles produced by radioactive materials, by heated materials and by illuminated materials were universal. The name electron was again proposed for these particles by the Irish physicist George F. Fitzgerald, and the name has since gained universal acceptance. While studying naturally fluorescing minerals in 1896, the French physicist Henri Becquerel discovered that they emitted radiation without any exposure to an external energy source. These radioactive materials became the subject of much interest by scientists, including the New Zealand physicist Ernest Rutherford who discovered they emitted particles. He designated these particles alpha and beta, on the basis of their ability to penetrate matter. In 1900, Becquerel showed that the beta rays emitted by radium could be deflected by an electric field, and that their mass-to-charge ratio was the same as for Cathode Rays. This evidence strengthened the view that electrons existed as components of atoms. The electron's charge was more carefully measured by the American physicist Robert Millikan in his oil-drop experiment of 1909, the results of which he published in 1911.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Research World(Publisher)
However, this produced a value that was more than a thousand times greater than what was expected, so little credence was given to his calculations at the time. ________________________ WORLD TECHNOLOGIES ________________________ In 1896, the British physicist J. J. Thomson, with his colleagues John S. Townsend and H. A. Wilson, performed experiments indicating that Cathode Rays really were unique particles, rather than waves, atoms or molecules as was believed earlier. Thomson made good estimates of both the charge e and the mass m , finding that cathode ray particles, which he called corpuscles, had perhaps one thousandth of the mass of the least massive ion known: hydrogen. He showed that their charge to mass ratio, e / m , was independent of cathode material. He further showed that the negatively charged particles produced by radioactive materials, by heated materials and by illuminated materials were universal. The name electron was again proposed for these particles by the Irish physicist George F. Fitzgerald, and the name has since gained universal acceptance. While studying naturally fluorescing minerals in 1896, the French physicist Henri Becquerel discovered that they emitted radiation without any exposure to an external energy source. These radioactive materials became the subject of much interest by scientists, including the New Zealand physicist Ernest Rutherford who discovered they emitted particles. He designated these particles alpha and beta, on the basis of their ability to penetrate matter. In 1900, Becquerel showed that the beta rays emitted by radium could be deflected by an electric field, and that their mass-to-charge ratio was the same as for Cathode Rays. This evidence strengthened the view that electrons existed as components of atoms. The electron's charge was more carefully measured by the American physicist Robert Millikan in his oil-drop experiment of 1909, the results of which he published in 1911.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Learning Press(Publisher)
However, this produced a value that was more than a thousand times greater than what was expected, so little credence was given to his calculations at the time. ________________________ WORLD TECHNOLOGIES ________________________ In 1896, the British physicist J. J. Thomson, with his colleagues John S. Townsend and H. A. Wilson, performed experiments indicating that Cathode Rays really were unique particles, rather than waves, atoms or molecules as was believed earlier. Thomson made good estimates of both the charge e and the mass m , finding that cathode ray particles, which he called corpuscles, had perhaps one thousandth of the mass of the least massive ion known: hydrogen. He showed that their charge to mass ratio, e / m , was independent of cathode material. He further showed that the negatively charged particles produced by radioactive materials, by heated materials and by illuminated materials were universal. The name electron was again proposed for these particles by the Irish physicist George F. Fitzgerald, and the name has since gained universal acceptance. While studying naturally fluorescing minerals in 1896, the French physicist Henri Becquerel discovered that they emitted radiation without any exposure to an external energy source. These radioactive materials became the subject of much interest by scientists, including the New Zealand physicist Ernest Rutherford who discovered they emitted particles. He designated these particles alpha and beta, on the basis of their ability to penetrate matter. In 1900, Becquerel showed that the beta rays emitted by radium could be deflected by an electric field, and that their mass-to-charge ratio was the same as for Cathode Rays. This evidence strengthened the view that electrons existed as com-ponents of atoms. The electron's charge was more carefully measured by the American physicist Robert Millikan in his oil-drop experiment of 1909, the results of which he published in 1911.
eBook - PDFScience In The Making
1850-1900
- E. A. Davis(Author)
- 1997(Publication Date)
- CRC Press(Publisher)
If the inner cylinder has initially a positive charge it rapidly loses that Y:2 VOLUME 2: 1850-1900 296 Prof. J. ,J. Thomson on Cathode Rays. charge and acquires a negative one; while if the initial charge is a negative one, the cylinder will leak if the initial negative potential is numerically greater than the equilibrium value. Diflexion of the Catltode Rays by an Electrostatic Field. An objection very generally urged against the view that the Cathode Rays are negatively eleetrified particles, is that hitherto no deflexion of the rays has been observed under a small electrostatic force, and though the rays are deflected when they pass near electrodes connected with sources of large differences of potential, such as induction-coils or electrical machines, the deflexion in this case is regarded by the snp-porters of the retherial theory as due to the discharge passing between the electrodes, and. not primarily to the electrostatic field. Hertz made the rays travel between two parallel plates of metal placed inside the discharge-tube, but found that they were not deflected when the plates were con-nected with a battery of storage-cells ; on repeating this experiment I at first got the same result, but subsequent experiments showed that the absence of deflexion is due to the conductivity conferred on the rarefied gas by the Cathode Rays. On measuring this conductivity it was found that it diminished very rapidly as the exhaustion increased; it seemed then that on trying Hertz's experiment at very high exhaus-tions there might be a chance of detecting the deflexion of the Cathode Rays by an electrostatic force. The apparatus used is represented in fig. 2. Fig. 2. The rays from the cathode 0 pass through a slit in the anode A, which is a metal plug fitting tightly into the tube and connected with the earth ; after passing through a second slit in another earth-connected metal plug B, they travel between two parallel aluminium plates about 5 em.
eBook - PDFFlash of the Cathode Rays
A History of J J Thomson's Electron
- Per F Dahl(Author)
- 1997(Publication Date)
- CRC Press(Publisher)
Wien himself took up cathode ray studies in early 1897. In so doing, he joined his countrymen Wiechert and Kaufmann (and, to some extent, Lenard, we might add) in establishing the particulate nature of cathode 266 Positive Rays rays, simultaneously with J J Thomson abroad. Using one of Lenard's vacuum tubes which, equipped with an aluminum window, allowed the rays to pass into a tube extension with a highly rarefied vacuum, he first confirmed Jean Perrin's discovery two years earlier that the rays consist of high-velocity negatively charged particles [15-5]. By magnetic and electrostatic deflection he also found that the particles have a velocity about equal to one-third that of light, and a mass-to-charge ratio of 5 x w-8 g emu -l, in qualitative agreement with e I m values for electrons deduced by his colleagues at home and abroad. The following year, having pursued the Cathode Rays to his satisfaction, he turned to a more timely question, the nature of Goldstein's Kanalstrahlen . . . . the thought came to me that the canal rays observed by Goldstein, which cannot be deflected appreciably by ordinary magnets, and which proceed backwards through a pierced cathode, might carry the positive charge. In this case it was not possible to shut out the field of observation completely from the discharge tube, because in spite of many attempts I could find no substance through which the canal rays will pass. [15-6] The apparatus that finally did the trick is depicted in figure 15.1. Here, the 'canal' is simply a 2 mm hole bored in an iron plate K (the cathode), to which glass tubes are cemented on each side. The anode is sealed into the far end of the left-hand tube, as shown. In the right-hand tube a pair of electrodes are mounted, spaced 1.7 em apart and connected to a high-voltage accumulator.
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