Why does a cathode ray tube have low pressure inside?
pressure inside the tube! In a cathode ray tube, the “cathode ray” is an electron beam that is used to paint a “picture” on the phosphor coating on the inside of the tube. (We look at the “picture” from the other side of the glass on which the coating is laid down – the outside.) An electron is a lightweight little dude. It weighs about 1/1836th as much as a single proton, so anything, any gas atoms that are in the flight path of an electron will cause it to scatter. That means we need to pump all the air out of the inside of the tube. After we remove all we can, we fire a “getter” (a chemical coated onto a small area inside the tube) which will bind any remaining gas molecules left inside the tube to complete the evacuation process. No more pesky atoms to get in the path of the electron beam and scatter it all over the place.
