why cathode-ray tube connected to a vacuum pump?

Question

anonymous · Answer

It is not connected to a vacuum pump necessarily but it does have a vacuum inside of it. The reason is the cathode send out a beam of electrons in order to activate the phosphorescent layer on the CRT (lets say the tv screen). The stream of electrons is relatively weak in term of what it is able to penetrate at the same time it has to be acurately deflected by the magnets so that it can Accenture hit a pixel on the tv screen. So if the CRT had air in it the air molecules would get in the way of the electron beams and cause them to be partially absorbed and mis-directed. Also if it had air in it it would expand and crack the actual tube because it would overheat due to the high energy of the electrons.

anonymous · Answer

and your question is?