Wikijunior:How Things Work/Television
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Most televisions and other displays around today use cathode ray tubes, which have three important parts. First is the cathode, which sends out a spray of electrons. Second are the focusing and deflecting coils, which shape that spray into a stream and then aim it at the third part, the screen, which has a phosphorus coating. The phosphorus lights up when it gets hit by electrons, and by lighting up different parts of the screen and leaving others dark, the CRT makes an image.
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[edit] Who invented it?
Several people contributed to the invention of television. Each person did a little at a time.
These three people seem to have been the major inventors:
Vladimir Kosma Zworykin developed a primitive television camera.
Philo Taylor Farnsworth was the first to successfully demonstrate the transmission of television signals.
John L Baird achieved the first transmissions of images of face shapes by means of television.
[edit] How does it work?
By plugging to an electric outlet.
[edit] How dangerous is it?
A very high voltage is needed to produce the energy needed to start and run a Cathode Ray Tube (CRT) and there is a risk of this high voltage causing severe electric shocks.
Televisions have many dangerous parts secured in a cabinet to prevent people from hurting themselves.
[edit] What does it do?
A televison is essentially a radio receiver with pictures. Signals similar to a radio's are received by the television antenna and sent to the receiver where they are sorted out.
Part of the signal is used to provide the sound you hear. The other part is used to create an image.
To get the image to appear like it is moving, thousands of still pictures are sent and displayed one right after another to give the impression that the image is actually moving.
The first black and white televisons used a series of lines which were thick in some places and thin in others. If you looked very closely at a black and white television screen which was showing the letter "A". It would appear like the image below.
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Today, all color televisions display a series of dots which change color depending on the image being displayed. If you look very closely at this screen you will see what I mean.
[edit] How does it vary?
[edit] How has it changed the world?
The television has changed the world in good and bad ways. The good ways are such as cooking shows, educational TV, V-Chips, etc.. adult swim, cost of satellite and cable TV, etc..
