thanks
2006-09-23 22:29:40 · 7 answers · asked by R.C 1 in Science & Mathematics ➔ Physics
vacuum means evacuation of the atmosphere. in engineering it is measured in millibar-10power -3 bar is equivalent to 1 torr.
in other words negative pressure ,lesser presence of atmospheric gases.
the number of gas molecules will be less.
in a crt tube the electrons with negative charge are attracted towards the screen and they form the pattern based on the receptive electrical /electromagnetic signal on the screen. if there is atmospheric pressure or gases present the electrons emitted from the cathode will end up ionising the gas present because of its relevant negative charge and it will be leading to the distortion of the image pattern. so to avoid this ionisation we are creating the vacuum. our television sets at home are also one king of crt only.if vacuum is not there to a high degree, then imagine there will be no reception in our tv sets.
2006-09-24 02:09:51 · answer #1 · answered by kailash s 2 · 0⤊ 0⤋
A cathode ray is a beam of electrons. A cathode ray is stopped after in trouble-free terms some inches in air. Electrons in air could collide with the air molecules and the beam does no longer be waiting to holiday very far. The electrons in air are scattered in distinctive guidelines inflicting the beam to become worse, and a few electrons are stopped completely. The vacuum ensures the beam travels accurately and to date because it needs to.
2016-12-12 13:59:19 · answer #2 · answered by Anonymous · 0⤊ 0⤋
Electrons travel from one end to the other inside the cathode ray tube. A steady flow of these electrons give you a steady luminacence. If there is air in CRT, the particles of air will collide with electron, and it might even result in explosion.
2006-09-23 22:40:02 · answer #3 · answered by pranesh81 3 · 0⤊ 0⤋
A vacuum is needed to prevent the electrons from 'scattering' by colliding with gas atoms or molecules. This allows the beam to be focused to a small point to form a tiny dot on the phosphor coating of the CRT.
Doug
2006-09-23 22:32:46 · answer #4 · answered by doug_donaghue 7 · 2⤊ 0⤋
The basic answer is because the electrons produced by the electron gun will be scattered by the molecules of air in the tube if it is not evacuated.
2006-09-23 23:59:14 · answer #5 · answered by JamesD 3 · 0⤊ 0⤋
if there is air (oxygen) in the tube, when it starts to get hot, the element would burn (there is no oxygen in a vacuum) and the tube would cease to function.
2006-09-23 22:39:09 · answer #6 · answered by Anonymous · 0⤊ 0⤋
Because if you don't put one in and it doesn't work, all your technician friends will make fun of you.
2006-09-23 22:31:50 · answer #7 · answered by The Lobe 5 · 0⤊ 1⤋