What is Cathode ray tube: Definition and 46 Discussions

A cathode-ray tube (CRT) is a vacuum tube containing one or more electron guns, the beams of which are manipulated to display images on a phosphorescent screen. The images may represent electrical waveforms (oscilloscope), pictures (television set, computer monitor), radar targets, or other phenomena. A CRT on a television set is commonly called a picture tube. CRTs have also been used as memory devices, in which case the screen is not intended to be visible to an observer.
In television sets and computer monitors, the entire front area of the tube is scanned repeatedly and systematically in a fixed pattern called a raster. In color devices, an image is produced by controlling the intensity of each of three electron beams, one for each additive primary color (red, green, and blue) with a video signal as a reference. In modern CRT monitors and televisions the beams are bent by magnetic deflection, using a deflection yoke. Electrostatic deflection is commonly used in oscilloscopes.

A CRT is a glass envelope which is deep (i.e., long from front screen face to rear end), heavy, and fragile. The interior is evacuated to approximately 0.01 pascals (9.9×10−8 atm) to 133 nanopascals (1.31×10−12 atm), to facilitate the free flight of electrons from the gun(s) to the tube's face without scattering due to collisions with air molecules. As such, handling a CRT carries the risk of violent implosion that can hurl glass at great velocity. The face is typically made of thick lead glass or special barium-strontium glass to be shatter-resistant and to block most X-ray emissions. CRTs make up most of the weight of CRT TVs and computer monitors.Since the late 2000s, CRTs have been superseded by flat-panel display technologies such as LCD, plasma display, and OLED displays which are cheaper to manufacture and run, as well as significantly lighter and less bulky. Flat-panel displays can also be made in very large sizes whereas 40 in (100 cm) to 45 in (110 cm) was about the largest size of a CRT.A CRT works by electrically heating a tungsten coil which in turn heats a cathode in the rear of the CRT, causing it to emit electrons which are modulated and focused by electrodes. The electrons are steered by deflection coils or plates, and an anode accelerates them towards the phosphor-coated screen, which generates light when hit by the electrons.Before the invention of the integrated circuit, CRTs were thought of as the most complicated consumer electronics product.

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  1. J

    What are the limitations of CRT display technology? resolution, nits, ....

    I've been reading about how color crt displays work because I've become interested in trying to make one, even if it isn't going to be very good compared to the ones of the past. (yes I know they have high voltage that can arc through material/ air and that voltage drop and electron collisions...
  2. cemtu

    I Why Bremsstrahlung <20keV for Tungsten?

    https://www.researchgate.net/figure/Bremsstrahlung-and-characteristic-radiation-spectra-are-shown-for-a-tungsten-anode-with_fig4_8365056 Fast electrons produce X-rays in the anode of an X-ray tube through two different methods. The first one is the interaction of electrons with the nuclei of...
  3. 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...
  4. C

    A How making the ions leave the cavity in a ion sources

    Ion sources are devices that allow creating ion beams (e.g. argon ions) and to project them outside the device, for example to be further processed by a particle accelerator, or to irradiate materials or biological tissues etc. The ions are usually created by a plasma inside a cavity filled...
  5. 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...
  6. T

    JJ Thomson Discovery of the Electron

    pg. 243 Falconer, I. (1987) Corpuscles, Electrons and Cathode Rays: J.J. Thomson and the Discovery of the Electron. The British Journal for the History of Science (BJHS, 1987,20,241-276). "One of their most important properties is that they are deflected by a magnetic field. This provided strong...
  7. 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...
  8. 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...
  9. 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...
  10. W

    B Related to - Thermionic emission

    Hey currently I am doing O levels and in my textbook I read that when a metallic wire (in CRO - the cathode) is heated up, it starts emitting its free electrons (thermionic emission). And also its a fact that electrons are responsible for electrical conductivity. A question just popped up in my...
  11. moenste

    Calculate the deflection sensitivity in mm per volt

    Homework Statement Describe a method by which the charge / mass ratio e / m of the electron has been determined. Calculate the deflection sensitivity (deflection of spot in mm per volt potential difference) of a cathode ray tube from the following data: electrons are accelerated by a...
  12. 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.
  13. 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
  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

    Year 12 EEI - Cathode Ray Tube

    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. M

    Please help on my Cathode ray tube experiment

    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...
  21. 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...
  22. 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...
  23. 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...
  24. 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...
  25. 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...
  26. 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...
  27. 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...
  28. 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?
  29. 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?
  30. 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.
  31. 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...
  32. 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...
  33. 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...
  34. 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...
  35. 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...
  36. 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?
  37. 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...
  38. P

    Understanding Cathode Ray Tubes: Exploring Electron Movement

    Can somebody please explain what actually happens in cathode ray tube? Is there any current passing through the tube? How does the anode (positive electrode) lost electrons? Is it before the effect of cathode rays? How does the cathode (negative electrode) have bigger amount of electrons? Is it...
  39. A

    Why Don't Electrons Stick to the Anode in a Cathode Ray Tube?

    Homework Statement I'm have a little problem with understanding the workings of a cathode ray tube. I understand that a filament is heated and that in turn heats the cathode which, due to thermionic emission emits electrons. OK so here is my problem. A positively charged anode is used to...
  40. A

    Electron in magnetic field and cathode ray tube

    If the motion of an electron creats a magnetic field around it then why is an electron beam in a cathode ray tube deflected at right angles and not towards the magnetic field? Also, what would be the effect of a magnetic field on a stationary (relative to the field)electron?
  41. H

    Finding Deflection of Electron Beam in Cathode Ray Tube

    Homework Statement I have to find out a relationship between the deflection of an electron beam in a cathode ray tube and the accelerating voltage. Homework Equations I know that theoretically D is inversely proportional to the accelerating voltage. The Attempt at a Solution I have to...
  42. P

    Cathode Ray Tube: Positive End & Electrons Explained

    Why is the end of the hot filament where negatively charged electrons are being fired called the cathode end. 'cat' in chemistry means positive, I assume the same goes in physics as well?
  43. Y

    Expression for vertical deflection in a cathode ray tube

    i need to find the expression for the vertical direction of a beam in a cathode ray tube, using: Va - accelerating voltage (between cathode &anode) Vd - deflecting voltage ly - effective length of deflecting plates L - distance from end of plates to the screen d...
  44. G

    Difference between a cathode ray tube and a magnetron?

    Can someone please explain to me the difference between a cathode ray tube and a magnetron? I just started using a magnetron for sputter deposition in a project for a prof, and after reading about it, it seems to be the same. Just wondering, even though it may be a stupid question! Thanks!
  45. P

    How can I calculate the deflection of an electron in a cathode ray tube?

    Its funny how one can forget how to do very simple things. :rolleyes: Here is a problem I've been working on and have a mental block and can't get the darn solution. It's from Krauss's EM text Note: Assume non-relativistic motion. I'm assuming beam enters between places with d/2 on each...
  46. G

    Cathode Ray Tube: Deflection on Screen with 480V & 36V, 960V & 18V

    In a Cathode Ray Tube, the deflection on the screen is 2.4cm when the accelerating voltage is 480V, and the deflecting voltage is 36V. What deflection will you see on the screen if the accelerating voltage is 960V and the deflecting voltage is 18V?
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