What is the physics of television?

Answer 1

Here's the short version. Grab a seat and buckle up. We see things with our eyes and hear things with our ears. If we could capture these things and broadcast them, we could capture them and could share them with one or many people at some distance from where we are. That's the idea behind television. It's what we see and hear here sent to a remote location - which 'tele' and 'vision' are. If we capture activities with a video camera (using charged coupled devices instead of the "old school" image orthicons), we can turn that action (or the light from it) into an electronic signal. A similar "conversion" is made with the sound, which is captured in a microphone - a device that converts the mechanical energy of sound to electrical energy (an electronic signal). Grab these and combine them, and then run them through a transmitter (modulate a carrier signal) and spit them out to an antenna. We're on air! In a remote location, put up an antenna and direct it toward the transmitter. Connect a television set to the antenna. Turn it on and tune in. The broadcast signal was sent out on a "channel" which has a specific frequency allocation. The receiver in the TV grabs that signal, and it amplifies it. The signals are then demodulated, and the video and audio signals are separated out and sent to other stages for processing. Audio goes to an audio amp and then to the speaker. The video signals are handled by color (red, green and blue), and then "set up" for presentation on a screen. In the "old school" TV with the cathode ray tube (CRT), the electron beams (the cathode rays) "paint" the picture on the screen a line at a time. Further, to avoid "fading" from the top of the picture to the bottom of the picture during one "frame" of that picture, the lines are painted in alternating "fields" of all the odd number lines and then all the even number lines. What's the result? A color picture with sound. Some links are provided for further information.