What is a cathode ray tube's phosphor screen?

Answer 1

It works on the following principles : (i)thermionic emission (ii)deflection of the electron beam by the electric and magnetic field (iii)fluorescence produced by the electron beam on a fluorescent screen

Answer 2

A cathode ray tube is a specialized vacuum tube in which some kind of visual presentation is created when an electron beam strikes a phosphorescent surface.

The beam is generated starting at an element called a cathode. It is heated by a heating element, and this causes thermionic emission, which is a phenomenon where electrons are "driven out of" the metal into an area just around it because of the thermal energy. The electrons form what is called a space charge right there. If we apply a high positive voltage to the front of the tube (which is coated with phosphors), it will attract the negatively charged electrons. They will be accelerated across the space (and through the vacuum) between the cathode and the screen, which is the anode. The electrons are the "cathode rays" we name the tube for. Another term we sometimes use is beam current (after electron beam).

Between the two elements we've identified are other elements. One is close to the cathode, and it's the control grid. It's a kind of pinhole in a metal disk, and we always apply a negative voltage there, the electrons, which want to fly to the big positive charge, will be partially blocked. The control grid "controls" the electron flow. If we apply a bit of negative voltage on the control grid, some beam current will flow. The more we drive the control grid negative, the less beam current flows. The electrons are flying to the anode in the front of the tube and striking the phosphor coating. This cause them to be excited and emit light. The phosphor coating is on the inside of the heavy glass "front" of the tube.

We'll have things ahead of the control grid that will focus the beam, and then we'll use one of two basic methods to "direct" or "aim" or "sweep" the beam (magnetic or electrostatic deflection). Think of the beam as a pencil of electrons writing on the front of the tube. It writes very quickly by scanning across in a line, turning off and "retracing" to get back to the other side, and then scanning another line below the last one. The beam is turned on and off (modulated) a little, a lot, or something in between as it sweeps. It paints an image of some kind by scanning all the lines. Then it repeats. This is the basic operation of the cathode ray tube. You'll want a link to do some follow up, and you can find one below.

Answer 3

A type of vacuum tube that forms an electron beam (aka cathode ray) instead of just a diffuse cloud of electrons. There are literally millions of kinds of cathode ray tubes designed for various purposes:

• x-ray tube
• picture tube
• vidicon tube
• iconoscope tube
• image orthicon tube
• image dissector tube
• williams tube (a type of DRAM used in early computers)
• oscilloscope tube
• graphechon tube (a dual CRT used for video scan conversion, e.g. 50Hz frames to 60Hz frames, circular radar scan to rectangular scan)
• etc.

Answer 4

A cathode ray tube is in the monitor. A hot filament at the rear end of the tube releases electrons. They are negatively charged particles. They are drawn toward a plate which has a positive charge. As they fly toward the plate, electro magnets turn on and off real fast and alter their paths. When they hit the screen, they land on a little dot of a particular color. You see a number of these dots lit up. They combine inside your eye to produce the picture. After the electron hits the screen, it falls down to the positively charged plate.

Answer 5

Cathode-ray tubes were first made with a single electron gun .The stream of electrons were accelerated towards the phosphor coated screen producing a monochrome image. Later developments introduced 3 electron guns aiming their electrons on to 3 different colour phosphors to produce a full colour image. CRT stands for Cathode-ray tube and is a type of thermionic valve and are used in either a TV or a computer screen. If these devices did not have any cathode-ray tubes you would not see an image. New LCD/TFT screens do not need the very high voltages required for CRT's.

Answer 6

When air inside a glass tube was removed, and a high voltage was applied to two electrodes inside the tube, an electric current would pass through the remaining gas, proving that gas was not only an insulator, but also a conductor. This current produces a ray from the cathode (negative electrode) that goes to the anode (positive electron). The beam would cause the fluorescent screen at the end of the tube to glow.

Answer 7

No equations or diagrams here. Simply the heated cathode gives off negative electrons are attracted to the positively charged screen. Plates and coils focus and steer the beam of electrons. When the electrons strike the screen the phosphorus coating lights up.

Answer 8

A cathode ray is a beam of electrons :

You could use it to amplify a signal (vacuum tubes)

you could bombard a metal plate and produce X-rays,

You could modulate it and have it hit phospher dots - and make a television picture.

Answer 9

The cathode ray is a beam of electrons. They go from the cathode to the positively charged screen. They are guided electrically and magnetically.

Answer 10

The phosphor screen itself consisted of a layer of phosphor dots that coated the inner surface of the CRT's faceplate