Cathode ray Definition and 66 Threads

Cathode rays (electron beam or e-beam) 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 (the electrode connected to the negative terminal of the voltage supply). They were first observed in 1869 by German physicist Julius Plücker and Johann Wilhelm Hittorf, and 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 previously unknown negatively charged particle, which was later named the electron. Cathode-ray tubes (CRTs) use a focused beam of electrons deflected by electric or magnetic fields to render an image on a screen.

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  1. sol47739

    I Postive rays in cathode ray tube experiments?

    I read in the following book A history of the sciences by Stephen F. Mason. About the discovery of the electron the write what I attached in the picture. I wonder what do these positive rays traveling in the opposite direction they talk about consist of? Some ions or what? I understand that the...
  2. garthenar

    Solving for a neutralizing B0 in a Thomson Cathode Ray (Algebra?)

    I've attached a picture from the problem, the given equations, and my work so far. I knew I had a problem when My units wouldn't check out. This should just be simple algebra but It's not working. Please help me to understand what I am doing wrong.
  3. F

    How do we know the mass of an electron?

    I've been researching the proof of subatomic particles given the fact that we have never seen them before. It has always been recognized that protons, electrons, and neutrons exist; but I question how we know for certain they exist. Across my studying I've realized that in 1897, J. J. Thompson...
  4. A

    Obtain Cathode Ray Tubes Without X-rays

    Good Day, I would like to obtain cathode-ray tubes for deflecting electrons with a magnet. However, I don't want to deal with X-rays, and would prefer to obtain cathode tubes that cannot produce X-rays at all. I haven't had much luck on the internet finding such cathode ray tubes or I don't...
  5. Robin04

    Electrons in a cathode ray tube

    Homework Statement The accelerating voltage in a cathode ray tube is ##1000 V##, the electron current density is ##150 \mu A##. a) How many electrons arrive at the screen in a second? b) What's the magnitude of the force exerted on the screen by the electrons if they stop on collision? (Sorry...
  6. dholbach

    Can a cathode ray tube be made from a light bulb?

    Light bulbs and cathode ray tubes are structurally similar in some respects. For example, both contain a filament -- in the light bulb, the filament heats up to produce light, while in a cathode ray tube, the filament emits electrons, which are then steered into a target (in a CRT TV, the...
  7. O

    Cathode ray tube, Voltage needed to move the beam impact spot

    Homework Statement Question: A cathode ray tube in a TV has an electron gun operating at 10 kV. a: What is the velocity (in m.s-1) at which the electrons are emitted? Answer:5.9x107 b: How many volts are needed between the deflector plates to move the beam impact spot across a 70 cm screen if...
  8. A

    Cathode Coatings for Electron Emission: Investigating Materials and Techniques

    Homework Statement What 3 materials is the cathode coated with, from which the electron originate? Homework Equations None The Attempt at a Solution From what I managed to find, I think some may be nickel and barium but I'm not sure.
  9. Chris Frisella

    EM Phenomenon: Magnetism from a Cathode Ray?

    I have recently studied about relativity being the reason for magnetism. The example given was about a magnetic field generated from current down a long wire. When two such wires with current in the same direction were parallel to each other there was an attractive force between them because...
  10. S

    Trace of cathode ray in changing magnetic field.

    I know that cathode rays follow a helical pattern if they enter a uniform magnetic field at an angle less than 90 degrees. This leaves me with two questions. 1. If the cathode ray described above, hit a phosphor coated screen, would it show only 1 spot or a circle? 2. If the magnetic field was...
  11. prashant singh

    What Happens When You Connect a 10,000 V Supply to a Normal Tube Light?

    suppose I connect a 10,000 v supply to a normal tube light. what will happen? will it behave like a cathode ray tube or something else
  12. S

    Exploring the Wave-Particle Duality of Electrons in CRT Monitors

    How do CRTs work well and electrons can be sent to exact location on screen in CRT monitors if electrons can behave like wave? Is there something in old TVs (for example measurement device) along the road that electron travels to avoid behave like wave?
  13. Plat

    Striations in cathode ray discharge

    What causes these striations? How does the voltage and pressure of the discharge affect the size, color, number, and spacing of the striations? I have produced a discharge with striations with fairly low voltage (under 15kv) and pressure 10 - 100pa, and the striations are very thin, compact, and...
  14. Andrew Wang

    Cathode Ray Tube and magnetic field Question

    Homework Statement A cathode ray tube (CRT), consisting of an electron gun and a screen, is placed within a uniform constant magnetic field of magnitude B such that the magnetic field is parallel to the beam axis of the gun, as shown in figure...
  15. Nemika

    Cathode ray tube- thermionic emission

    I have just learned about the cathode ray tube in the class room. There is a part called electron gun in it which emits electrons and these electrons finally strike the fluorescent screen.(I hope its correct till here.) But I want to ask that won't there be a loss of electrons in this process...
  16. B

    Cathode Ray Tube with magnetic field

    Homework Statement A solenoid is placed beneath a CRT that produces a magnetic field of 1.10 x -2. The CRT is 1 meter away from a screen. The electrons that make up the beam were accelerated from rest through a potential difference(V) at the beginning of the CRT. Acceleration of the electrons...
  17. N

    What Variables Can Be Changed in a Cathode Ray Tube Experiment?

    For my year 12 physics EEI (extended experimental investigation) i need to develop some sort of experiment with variables i can change to retrieve data from. I have a basic cathode ray tube from a few months ago much like the one in this video: . Does anyone have any idea of what variables i...
  18. J

    How many volts does a cathode ray tube emits?

    I don't know a lot about classical physics but I was wondering how many volts a cathode ray tube emits?
  19. S

    Accelerating electrons in a cathode ray tube

    I have a question which has intrigued me for quite some time. If the electrons are accelerated using a potential difference in a cathode ray tube, the electrons should get accelerated till the time they reach the anode only. Once they cross over (ie. move to the other side of the anode), they...
  20. G

    J.J. Thomson's Cathode Ray Experiment: Discovery of Electrons

    Hi! I've been watching this video http://ocw.mit.edu/courses/chemistry/5-111-principles-of-chemical-science-fall-2008/video-lectures/lecture-2/ on the discovery of electrons , and I have some doubts about it. The lecturer explains the cathode ray experiment performed by J.J Thomson. This is...
  21. M

    How Can I Design Experiments to Observe Different Fluorescence Effects in a CRT?

    Homework Statement I am building a CRT for my physics project but have some doubts. I know there will fluorescence effect but my project requires to do an experiment and make observations. So how can I relate this experiment so that I have:- 1. Different cases and experiments with the CRT...
  22. A

    Build a CRT: DIY Instructions & Guide

    I've been looking to do a physics project, and since particle accelerators are too dangerous, I was thinking about building a cathode ray tube (CRT) I've done some research about building CRTs, and haven't been able to find anything that gives a complete list of how to build a CRT. Could anyone...
  23. skate_nerd

    Deflection of electron beam in cathode ray tube

    Homework Statement Part a) Deflection of the electron beam in a cathode ray tube television set has electrons accelerated until they have K.E. of 25 keV. What is the magnetic field magnitude required to deflect the electron beam 3.3 cm when the magnetic field is 8 cm long? Part b) When...
  24. A

    Cathode Ray Tube: Explaining Phenomena with Green Beam and Fluorescent Glow

    In a video demonstration (not animation), cathode rays appear as a beam of green light moving from the cathode to anode inside the tube. The demonstrator brings a magnet near the tube and the green beam deflects. This I can understand. What I can not understand is that how the electron beam...
  25. V

    Voltage spawning a cathode ray

    In descriptions of the cathode ray, various sites mention how the ray is formed from a voltage applied to the tube which spawns the ray on sees in the vacuum tube. Could someone elaborate on how a voltage can spawn this beam? As in, where does the potential difference come from and so on...
  26. J

    J.J. Thomson's cathode ray experiment

    In Rohlf's Modern Physics textbook it reads: "The value of q/m for the electron determined by Thomson wan substantially smaller than the values of q/m determined by electrolysis, that is, q/m for the electron is much smaller than for ionized atoms. There were two extreme possibilities: (1) The...
  27. D

    Cathode ray create interference pattern?

    If I were to construct a cathode ray tube in which the beam of electrons was focused on a double slit, behind which was a screen of phosphorous, could I create an interference pattern? Could this setup be made at home? I imagine making the slits would be the most difficult part. Or is this...
  28. M

    Cathode Ray Tubes: Understanding the Role of Cathodes

    From my current understanding, a cathode is an electrode which has conventional current flowing OUT of it (or electrons flowing INTO it) while an anode had conventional current flowing INTO it (or electrons flowing OUT of it). From this definition, I don't understand why the electrode which...
  29. P

    Archived Displacement and Momentum, particle in cathode ray tube with variables

    Homework Statement In a cathode ray tube (CRT) used in older television sets and oscilloscopes, a beam of electrons is steered to different placed on a phosphor screen, which glows at locations hit by electrons. The CRT is evacuated, so there are few gas molecules present for the electrons to...
  30. P

    Understanding Cathode Ray Discharge and Electron Knockout

    When a high voltage is applied across the electrodes of the discharge tube, and the pressure of the gas inside the tube is lowered, the electrical energy knocks out some of the electrons from the atoms. These constitute the cathode rays. How does electrical energy knocks out electrons is...
  31. L

    Electrostatics problem (electron's motion in cathode ray tube)

    Homework Statement Homework Equations Fq=E*q kinematics equations... The Attempt at a Solution The problem is that in the end I get a value ABOVE the mid-axis instead of below. I don't know what I'm doing wrong. Please check my reasoning. Stage 1: While it's in between the plates where...
  32. M

    Trajectory of an electron in cathode ray tubes

    Why is it that an electron traveling under the influence of a magnetic field (i.e electron going from left to right and B field going into the page) will travel in the arc of a circle yet when an electric field alone is applied (say up page and the direction of motion of the electron is the...
  33. A

    J.J Thompson's Cathode Ray Experiment

    When Thompson conducted his cathode ray experiment, how did he know that the negatively charged electrons were so small? He knew that they were deflected in measurable ways by electric and magnetic fields, so he concluded that they must have a very small mass to charge (m/e) ratio. But that...
  34. J

    How does a cathode ray eject inner orbital electrons?

    (Since this is a coursework question and not a homework question, I deleted the template) Both my chemistry and physics textbooks cite cathode rays as having the ability to excite or eject electrons from an atom (e.g., dielectric breakdown, x-ray spectroscopy). How can a stream of negatively...
  35. D

    Cathode Ray Tube Lab: Proving D=Vd/Va{(L1^2+2L1L2)/4d}

    I'm not even sure if it belongs in here... but my class is assigned to do this lab the objective is to determine that D=Vd/Va{(L1^2+2L1L2)/4d} is correct... so my teacher also want us to do 2 graphical analysis based on this formula I think i found one way of doing graphical analysis (if i...
  36. D

    Calculating Electron Kinetic Energy in a Cathode Ray Tube

    Homework Statement Have a few questions on CRT's. If we are given the accelerating voltage (250V) how would I calculate the kinetic energy of the electron as it leaves the positive end of the charge area? What is the formula for the speed of an electron along the tube (vz) as it leaves the...
  37. E

    Build a Cathode Ray Tube - Experiment & Reference Guide

    I would like to build a cathode ray tube like this one: http://www.youtube.com/watch?v=XU8nMKkzbT8". It would be pretty damn cool playing with electrons. Do you know any references about this experiment? I mean, How could I build a glass vail and are there standard measures?
  38. P

    Thompson's cathode ray tube experiment

    Why couldn't Thompson just let one electron fly across the gap before disconnecting the battery and turning off the beam, and then measure the amount of charge deposited on the anode,thus allowing him to measure the charge of a single electron directly?
  39. D

    CRT High Voltage: Why Does It Need It?

    Why does a cathode ray tube (CRT) require a high voltage to operate?
  40. C

    Cathode Ray Tube: Electron Source & Ionization

    When my Tv shoots electrons from the cathode ray tube , where do these electrons come from and is it ionizing whatever they come from.
  41. T

    TV Cathode Ray Tube Consider a potential

    Homework Statement In an old TV cathode ray tube, electrons are accelerated by a potential of 15 kV between the gun and screen. Find: a) Kinetic energy of the electrons when they reach the screen b) Its respective wavelength c) Wavelength of the photons with maximum energy that are...
  42. M

    Cathode Ray Tube in a uniform magnetic field

    Homework Statement A CRT is placed in a uniform magnetic field B, with the axis of the tube parallel to the lines of force. If electrons emerging from the gun with a velocity v make an angle θ as they pass through the origin O so that their trajectory is a helix, show that a) they will touch...
  43. N

    Kinematics Electrons In a Cathode Ray Tube

    A) In a cathode ray tube, electrons are accelerated from rest by a constant electric force of magnitude 6.22 x 10−17 N during the first 2.00 cm of tube's length; then they move at essentially constant velocity another 46.5 cm before hitting the screen. Find the speed of the electrons when they...
  44. U

    How exactly do cathode ray tubes work?

    I learned from a website that cathode ray tubes fire electrons from an "electron gun" at the cathode towards the anode, hitting a piece of metal and produce cathode rays in the process. My question is; how do cathode tubes "shoot" electrons? Apparently it's due to a high potential difference...
  45. S

    Cathode Ray Tube Magnetic Question

    Homework Statement The figure from the link below shows a cross section of a cathode ray tube. An electron in the tube initially moves horizontally in the plane of the cross section at a speed of 2.0 x 107 meters per second. The electron is deflected upward by a magnetic field that has a...
  46. N

    Cathode Ray Type Question - Electron being moved by horizontal plates

    Homework Statement An electron is accelerated horizontally from rest in a television picture tube by a potential difference of 5710 V. It then passes between two horizontal plates 6.45 cm long and 1.24 cm apart that have a potential difference of 249 V (see figure below). At what angle q...
  47. S

    Solving Cathode Ray Tube Homework with Mass, Speed & Magnetic Field

    Homework Statement A positively charged particle of mass 7.2 * 10^-8kg is traveling east with speed of 85 m/s. The particle enters a 0.31 T uniform magnetic field, and 2.2 * 10^-3 secounds later leaves the field one-quarter south with speed of 85 m/s. What is the charge of the particle and...
  48. S

    Dissecting a cathode ray tube television

    I'm considering dissecting an old, color cathode ray tube television. Do cathode ray tube televisions have capicitors in them that could shock me?
  49. P

    Electron deflection in a cathode ray tube

    Homework Statement An electron in a cathode ray tube is accelerated through a potential difference of ΔV = 11 kV, then passes through the d = 4 cm wide region of uniform magnetic field. What field strength (in mT) will deflect the electron by 10(degrees)? (Hint: is it a reasonable...
  50. D

    How Are Electrons Deflected in Thomson's Experiment With Only a Magnetic Field?

    [SOLVED] Cathode Ray - No Electric Field Homework Statement Consider J. J. Thomson’s 2nd experiment, the discovery of the electron. Turn on a magnetic field, but turn off the electric field. If the electrons enter a region of uniform magnetic field B and length l, show that the electrons...
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