Jessica Robinson, of St Mary's School, asks :-

How does television work?

Bob Hodgson, an electrical engineer and technologist in the Department of Information Engineering at Massey University, responded.

Television enables us to see and hear beyond the normal natural limits.

For example, you may have been watching TV news showing people in other countries. A television camera works like an ordinary camera except that in place of photographic film it has an electronic sensor. The electronic sensor generates an electronic signal that depends on what the camera is pointed at. Most television cameras also have a built-in microphone to capture the sounds that go with the pictures. The signal that comes out of the camera can than be sent long distances on a radio wave.

The aerial on your television catches some of these radio waves and then your television set rebuilds a copy of the original electronic signal from the television camera. Your television set then uses the copied signal to produce the picture that you view. It does this in a rather neat way, a point of light is moved in a zigzag pattern on the television screen, and made brighter and darker as it goes. It does this so quickly that your eyes are fooled into thinking that you are seeing a real moving picture. So what does all this say? Well, television is really a rather clever electronic conjuring trick! If you close one eye and wave your hand in front of it while looking at the TV screen you will see dark regions.