The TV has an airless glass tube with an electron gun on one side and a screen coated with fluorescent material on the other. Thousands of electrons from the electron gun hit the screen, causing the fluorescent atoms to become excited. Fluorescent atoms continue to emit light according to their religion , so we see pictures. Even if the television is switched off, the excitability of the atoms is maintained for a while and the light glows. This is why even after turning off the switch, a glimmer of light can be seen on the TV screen.