That was a real problem with colour TV CRT's. They had a mask with tightly spaced holes just behind the phosphorous. You had to adjust it as best you could, involving lots of compromises...sawer said:
sawer said:
sawer said:
Svein said:
sawer said:
That wasn't a problem of QM. The dimensions of an electron gun (and the whole CRT) take matters way out of the region of diffraction. Any beam spreading and also the resulting lack of colour purity is down to the very tight margins for a shadow mask (and the subsequent improvements) and the fields which deflect the electron beam. Electrons can be treated as 'simple' charged particles when you're designing electron optics in this context, I'm sure.Svein said:
Possibly not, but wave interference was a real problem. TV presenters were not allowed to wear clothes with fine patterns...Drakkith said:
It was due to limitations of PAL and NTSC as well as interlacing jitterSvein said:
OMG. That's a bit of a wild guess; the orders of magnitude are all wrong for diffraction.Svein said:
It's to do with the colour coding on the signal and it's there on the drive to the tube. In PAL and NTSC, there is a 'subcarrier' at 4.43MHz (PAL), which carries the colour (chrominance) information. This subcarrier forms beats with high frequency video components. These beats are whet you see when the picture content is stripy. A 4.2 MHz grille will produce 230kHz fringes - very visible. The effect is not as visible on single sharp edges so the picture is ok if you avoid regular hf patterns.A detail that the diagram does not show is that the three beams have to come from the same virtual point in space, despite the electron guns and grids are fairly wide, so the shadow mask works onver the whole screen. (Also, the beams go through more than just one hole at a time to make the picture bright enough). The beams from the three guns have to be bent by magnetic fields to achieve this. No wonder those shadow mask tubes had to be set up every day for high quality stdio use. TGF LCDs.Svein said:
Svein said:
Vanadium 50 said:
The shirt problem was intermodulation, whatever he means. It happened on flat screen PAL receivers.Drakkith said:
The holes were close enough to create an optical grid...Drakkith said:
What wavelength would you assign to the electrons, though?Svein said:
A cathode ray tube is a vacuum tube that produces images by manipulating a beam of electrons. The tube is made up of an electron gun, which emits electrons, and a fluorescent screen, which displays the image. The gun shoots electrons towards the screen, creating a bright spot of light wherever it hits. By controlling the direction and intensity of the electron beam, the CRT can create images.
Quantum mechanics is a branch of physics that studies the behavior of particles at the atomic and subatomic level. It explains the strange behavior of particles, such as being in multiple places at once, and is essential in understanding the functioning of cathode ray tubes. The electron beam in a CRT behaves according to the principles of quantum mechanics, which allow for precise control and manipulation of the electrons.
Cathode ray tubes have been used in a variety of devices, such as televisions, computer monitors, oscilloscopes, and radar displays. They also played a crucial role in the development of early computers. Today, CRTs are still used in some specialized applications, but they have largely been replaced by newer technologies, such as LCD and LED displays.
The cathode ray tube played a key role in the discovery of the electron by J.J. Thomson in 1897. Thomson observed that the electrons in the CRT were negatively charged particles, which were later named electrons. This discovery revolutionized our understanding of the structure of atoms and led to further advancements in quantum mechanics.
Cathode ray tubes emit low levels of radiation, which can be harmful if someone is exposed to it for extended periods. The screens of CRTs are also coated with phosphors, which contain toxic substances such as lead and mercury. However, modern CRTs are designed to minimize these risks and, with proper handling and disposal, pose little risk to human health.