Screens How it works Cathode Ray Tubes Output devices Cathode Ray Tubes Television screens used to use a technology called cathode ray tubes CRT An electron gun emitted electrons inside a glass tube onto phosphor atoms at the end of the glass tube causing the phosphor atoms to ligh ID: 322664
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Slide1
Plasma Screens
‘How it works?’Slide2
Cathode Ray Tubes
Output devices
Cathode Ray Tubes
Television screens used to use a technology called, cathode ray tubes (CRT). An electron gun emitted electrons inside a glass tube onto phosphor atoms at the end of the glass tube, causing the phosphor atoms to light up. The electron gun scanned the screen many times per second, producing an image.
Cathode Ray Tube diagramSlide3
Plasma Screen
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Coloured Fluorescent Lights
A plasma screen works by illuminating tiny coloured fluorescent lights; a red, blue and a green light. The intensity of these three lights is varied so to make up different colours.
Varying each
light intensity produces an image.Slide4
Plasma Screen
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Plasma Screen Cell
Inside one of the lights is a gas, usually Xenon or Neon
A gas usually Xenon or Neon.
These atoms are neutrally charged, although when they become unstable they can release photons producing ultraviolet light. Slide5
Plasma Screen
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Passing Electricity
Electricity is then passed between the gas, Xenon and Neon.
Electricity passed through the Xenon and Neon gas.
This means that electrons flow through the gas freely.
Flow of electronsSlide6
Plasma Screen
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Atoms
Plasma is a gas, made up of free flowing
ions
(electrically charged ions) and electrons (negatively charged particles)
Introduce free flowing electrons into a gas
1
Electrons are forced from the gas atom.
The atom is now ionised as it is missing an electron
3
4
Negative electrons rush towards the ion releasing a photon in the process
2Slide7
Plasma Screen
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Ultraviolet to Visible Light
The ultraviolet light (photons) released when the ionised gas collides with negative electrons, produces
ultraviolet light
. The ultraviolet photons strike the surface of Phosphorus giving off
light
.
Introduce free flowing electrons into a gas
Negative electrons rush towards the ion releasing a photon in the process
Ultraviolet photon atoms are released
The ultraviolet light photons hit a phosphorous surface producing visible light. Slide8
Plasma Screen
Output devices
Ultraviolet to Visible Light
The ultraviolet light (photons) released when the ionised gas collides with negative electrons, produces
ultraviolet light
. The ultraviolet photons strike the surface of Phosphorus giving off
light
.
The ultraviolet light photons hit a phosphorous surface producing visible light.
Visible Light
Ultraviolet LightSlide9
Plasma Screen
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Summary
How do plasma screens work?
- They are made up of tiny fluorescent light cells of red, blue and green that produce light by varying their intensity.
Inside each cell is a neutral gas usually Xenon or Neon.
A controlled charge of electricity is passed through the gas allowing electrons to flow freely.
The electrons collide with the gas atoms, freeing electrons from the atoms and thus ionising the atoms giving them a positive charge.
The flowing electrons are drawn towards the ionised atoms and ultraviolet photons are released.
When the ultraviolet light hits a phosphorous surface, the ultraviolet light is transferred into visible light.