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Television

Television. Question:. A television image is created by beams of moving electrons that collide with the inside front surface of the television picture tube and cause it to glow. Will a magnet held still near the picture tube affect the image that forms?. Observations About Television.

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Television

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  1. Television

  2. Question: A television image is created by beams of moving electrons that collide with the inside front surface of the television picture tube and cause it to glow. Will a magnet held still near the picture tube affect the image that forms?

  3. Observations About Television • Radio waves carry an image somehow • Image can be black & white or color • Television takes a moment to turn on or off • Image is affected by magnetic fields • Photographs of televisions look funny

  4. Creating an Image • A television creates its image dot by dot • It scans the screen 60 times per second • A full frame is two scans – two fields • Our eyes are slow; we see continuous motion

  5. Fluorescence • Electrons collide with phosphors inside screen • Phosphors are electronically excited • Phosphors emit their excess energy as light • Different phosphors emit different colors

  6. Aiming the Electrons • Electrons are “boiled” off a hot wire • They’re accelerated toward positive charge • They’re focused and steered en route to screen • Focusing is electric and magnetic • Steering is magnetic

  7. Image Creation • Electron beam intensity variations are synchronized with the beam scanning • Patterns of dark and light create images • TV station provides the intensity information

  8. Color Television • Three colors all that’s required for color TV • Red, Green, and Blue are primary colors of light • Combining these can make us see any color • Color television has three phosphors: RGB • 3 electron beams illuminate those 3 phosphors • Shadow mask aids in hitting correct phosphor

  9. Question: A television image is created by beams of moving electrons that collide with the inside front surface of the television picture tube and cause it to glow. Will a magnet held still near the picture tube affect the image that forms?

  10. Digital Television • Analog TV transmits every dot via radio wave • Digital television encodes the image • Digitize image into a pattern of colored pixels • Compress out redundant, non-essential information • Transmit digital, compressed info via radio wave • Digital offers noise-free, high resolution TV

  11. Near Future of TV • Dual Transmissions: Analog & Digital • Phase-out of Analog TV (set top converters) • Flat-panel TV sets (LCD and Plasma) • VCR replaced by DVD and Digital Recorders

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