![]() ![]() Normal glass isn't particularly luminescent so tubes designed to produce light (like a CRT) are coated with phosphors. Basically, the electrons striking the glass excite components of the glass to an elevated electronic state which releases light upon returning to the ground state. The glow of the glass envelope is luminescence-either fluorescence or phosphorescence (or both). A potential placed between the cathode and the anode accelerates these electrons through the tube, at the front face of which they strike a phosphor screen. A filament near the cathode heats it, boiling electrons off it. 1855 German inventor Heinrich Geissler develops mercury pump - produces first good vacuum tubes, these tubes, as modified by Sir. In cold cathodes, electrons are released by field emission, where a large applied electric field allows electrons to tunnel away from a metal electrode. A cathode ray tube is an evacuated glass envelope having a cathode at the back, and an anode some distance in front of it. The electron beam is produced by thermionic emission in hot cathodes-electrons are liberated from a hot filament when the thermal energy is enough for electrons to exceed the filament's work function. The cathode ray tube or 'Braun tube' is a vacuum tube that contains electron guns pointed at a fluorescent screen. ![]() The image on CRT display is created by firing. If there's enough gas, you get a plasma rather than a beam of electrons. CRT is a technology used in traditional computer monitors and televisions. The vacuum doesn't have much to do with the production of electrons, per se, but without high vacuum, the electrons collide with gas particles before they travel very far. The sharp shadows produced by Crookes tubes meant that something was travelling in a straight line from the cathode down the tube, so they were named cathode rays. 3: The cathode ray tube was first invented by Sir. ![]() Crookes concluded that the cathode ray was made of particles which must have mass. Notice that the cathode and anode are positioned so that the rays will strike the top of the paddle wheel. The name exists because cathode ray devices predate the discovery of the electron. Upon starting up the cathode ray tube, the wheel rotated from the cathode towards the anode. "Cathode rays" are simply beams of electrons. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |