• Question: how in the world are the pickters on the tv come up on the tv through a wire

    Asked by olliep to Adam, Catherine, Karen, Leila, Nazim on 19 Mar 2012.
    • Photo: Karen Masters

      Karen Masters answered on 19 Mar 2012:

      The pictures on TV are put into a code which your TV can turn into picture. A picture on a TV is just a series of information about how bright the different coloured pixels on the TV should be. This might not be true of modern plasma screens, but if you have an old TV and look really closely you’ll see that it’s made up of lots of tiny different coloured dots (red/green/blue all close together). The signal coming down the wire tells each dot how bright it should be, and your eye puts all of those dots together into a picture.

    • Photo: Adam Stevens

      Adam Stevens answered on 19 Mar 2012:

      Like Karen says, modern tvs are just a digital code that tells each pixel what colour to be at a given time.

      Old school TVs were a bit more complex they had a cathode ray tube at the back that shot electrons at the screen, which made small bits called phosphors light up, giving colour. So the signal into the TV had to tell it how to move the electron beam around. Again this just would have been a particular code.

    • Photo: Leila Battison

      Leila Battison answered on 19 Mar 2012:

      Lots of the pictures on your TV don’t even come through a wire any more – they are sent as little digital bits of information from satellites down to the receiver in your TV set.

      The information that comes in is just packed in really tightly and tells your TV what colour to make each pixel on your screen. HD TVs have more pixels crammed into the space, and HD channels give out loads more information.

    • Photo: Nazim Bharmal

      Nazim Bharmal answered on 19 Mar 2012:

      In the same way that sounds come in through a radio aerial: the signals in the air cause the electrons in the aerial to vibrate, and this can be detected inside a radio (or TV). The electronics then can choose the different channels they want to be sensitive to by tuning (so you can watch one channel at a time) and then they chop up the signal into various bits: how bright the picture should be; what colour the picture should be; and what sound should be played.

      The TV then puts it all together, sends the sound to the speaker, and the picture to the electronics that show the image (which might be using LEDs, or a LCD, or a plasma technology, or if you have an old TV like mine, to a electron gun that fires electrons at the screen which then glows in the places you want a picture to appear).

      Old TVs, until recently used analogue signals like radio. Now modern TVs use digital signals, and you need an extra step to turn the digital signal into an analogue one before you can show it. But it does mean you get a clearer picture.

      One tiny extra fact: if a TV can’t pick up a signal, you see something called ‘snow’, which looks like fast moving black and white dots. About 1% of this signal is the echo left over from the big bang, so it is the signal from the beginning of the universe! Amazing, as Brian Cox might say 🙂