Television Facts



  • Television relies on the photoelectric effect – the emission of electrons by a substance when struck by photons of light. Light-sensitive photocells in cameras work like this.
  • TV cameras have three sets of tubes with photocells (reacting to red, green and blue light) to convert the picture into electrical signals.
  • The sound signal from microphones is added, and a ‘sync pulse’ is put in to keep both kinds of signal in time.
  • The combined signal is turned into radio waves and broadcast.
  • An aerial picks up the signal and feeds it to your television set.
  • Most TV sets arc based on glass tubes shaped like giant light bulbs, called cathode-ray tubes. The narrow end contains a cathode, which is a negative electrical terminal. The wide end is the TV screen.
  • The cathode fires a nonstop stream of electrons at the inside of the TV screen. TV cameras convert a scene into electrical signals that can be transmitted via radio waves.
  • Wherever electrons hit the screen, the screen glows as its coating of phosphors heats up.
  • To build up the picture the electron beam scans quickly back and forth across the screen, making it glow in certain places. This happens so quickly that it looks as if the whole screen is glowing.
  • Color TVs have three electron guns: one to make red phosphors glow, another for green and a third for blue.