Is electromagnetism present in the cathode ray tube of a television?

Answer 1

Yes, electromagnetism is a central factor in the Cathode Ray Tube. An electron emitter at the back of the Cathode Ray Tube (CRT) fires electrons toward the front of the tube. These electrons pass through two sets of parallel metal plates - one set is oriented horizontally and the other vertically. The CRT creates a variable strength electromagnetic field across each pair of plates, and as the electron passes between the plates, the trajectory of the electron is deflected up, down, left, and/or right - depending upon the polarity and magnitude of the magnetic field between the plates. By deflecting the trajectory of the electrons so, the CRT can selectively and accurately aim electrons at specific points, or dots, on the front of the CRT. The inside front surface of the CRT is coated with a photo luminescent material that emits a photon (light) of a specific frequency (color) when struck by the electron. By selectively coating materials that emit red, blue, and green light for each dot, or pixel, the CRT can create a broad range of colors. The deflector plates cause the electrons to scan left to right (when looking at the picture) starting at the top line, then left to right on the second line, and so on, until it scans left to right on the very bottom line. The CRT resets the deflector plates again to start at the top left dot, and repeats the cycle for the next frame. This process is called a progressive raster scan. Most television signals use an interleave scan, where the CRT scans left-to-right on all the odd numbered lines first, then resets to the top-left corner, and next scans left-to-right all the even numbered lines last to scan a frame. Thus, in an interleaved raster scan, it actually takes two successive scans to display a complete frame. On a North American television, that uses NTSC format, the television scans 525 lines per frame (486 visible lines), 30 frames per second. A link to the Wikipedia article on the CRT is provided.

Answer 2

Cathode Ray Tubes, or CRTs, are vacuum tubes usually containing 3 red green and blue electron guns and a fluorescent screen. This is what allowed old TVs to show pictures, though have also been used as memory devices. The beams within these CRTs are often bent by magnetic deflection, which allows the beams to be changed, and why magnets mess severely with these TVs.