How exactly do cathode ray tubes work?

In summary, cathode ray tubes work by firing electrons from an "electron gun" at the cathode towards the anode, resulting in cathode rays. This is possible due to a high potential difference between the anode and cathode, but unlike in arcs, the electrons travel through a hard vacuum instead of gas. The rays turn from blue to green when they hit a piece of metal due to the electrons striking a phosphor, which produces colors for TV and computer monitors.
  • #1
user111_23
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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 between the anode and cathode, but wouldn't that create an arc of electricity instead?

Also, why do the rays turn from blue to green when the electrons hit the piece of metal? I'm curious.
 
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  • #2
No, arcs occur because electrons moving through gas knock loose other electrons in the gas atoms, resulting in an ionized conductive path--once this happens, nearly unlimited currect can flow (this is the reason gas-dicharge lamps require current-limiting ballasts). In a CRT, there is a very hard vacuum so the electrons can travel from the gun to the screen virtually unimpeded.

user111_23 said:
Also, why do the rays turn from blue to green when the electrons hit the piece of metal? I'm curious.

I don't know what you mean here. The colors in a CRT are produced from the electrons striking a phosphor; in a TV or computer monitor there are three which fluoresce either red, blue or green. Combinations of these colors produce nearly the whole range of human-visible colorspace.
 
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  • #3


Cathode ray tubes work by using an electron gun to fire a stream of electrons from the cathode towards the anode. This electron gun consists of a heated filament that emits electrons and an anode that accelerates the electrons towards the cathode. The potential difference between the anode and cathode creates an electric field that pulls the electrons towards the anode, causing them to move at high speeds.

The electrons then pass through a tube filled with a low-pressure gas, usually a mixture of neon and argon. When the electrons collide with gas molecules, they transfer energy to the gas atoms, causing them to emit light. This light is what we see as the cathode rays.

As for the change in color from blue to green, this is due to the different gases used in the tube. Neon emits a reddish-orange light, while argon emits a blue-green light. The mixture of these gases creates a range of colors, with the dominant color being green.

It is important to note that the cathode ray tubes used in older televisions and computer monitors have largely been replaced by newer technologies. However, they are still used in certain specialized applications such as oscilloscopes and medical imaging devices.
 

1. How do cathode ray tubes produce images?

Cathode ray tubes work by using a heated cathode to emit electrons, which are then accelerated towards a positively charged anode. As the electrons pass through a narrow opening in the anode, they are focused into a beam and directed towards a phosphor-coated screen. When the electrons hit the screen, they cause the phosphors to emit light, creating the images we see on a cathode ray tube display.

2. What is the role of the electron gun in a cathode ray tube?

The electron gun is responsible for producing a focused beam of electrons in a cathode ray tube. It consists of a heated cathode, which emits electrons, and one or more anodes, which accelerate and focus the electrons into a narrow beam. The direction and intensity of the electron beam can be controlled by varying the voltage applied to the anodes.

3. How do cathode ray tubes create color images?

Cathode ray tubes use a combination of red, green, and blue phosphors to create color images. The electron beam is controlled by three separate electron guns, each producing a beam of a different color. These beams are then directed towards the respective phosphor dots on the screen, creating the illusion of a full-color image.

4. What is the purpose of the shadow mask in a cathode ray tube?

The shadow mask is a metal sheet with tiny holes that sits just behind the phosphor-coated screen in a cathode ray tube. Its purpose is to ensure that the three electron beams from the electron guns hit only the correct phosphor dots on the screen, preventing color bleeding and ensuring a sharp and accurate image.

5. How do cathode ray tubes produce a flicker-free image?

Cathode ray tubes produce a flicker-free image by using a high refresh rate. This means that the electron beam is rapidly scanning across the screen multiple times per second, creating the illusion of a steady and continuous image. In modern cathode ray tubes, the refresh rate is typically 60Hz or higher, resulting in a smooth and flicker-free display.

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