How do the pictures on computer screens get there?
Are you asking how the screens work? Most screens are "CRT", which
means "cathode-ray-tube", which is the same principle that a
TV uses (though usually with a different, higher, resolution).
There is an electron "gun" that turns rapidly on and off, scanning
the screen and exciting the "phosphors" on the surface that actually
give out the light. There are also liquid crystal and plasma
displays, both of which have many elements that are controlled
simultaneously, rather than a single scanning element.
Other than that, pictures get to computer screens because
people told the computers what to put there. Usually there is
a special area of computer memory (sometimes on a special graphics
card) that contains a map of the screen, with, say, a 1 for
a point on the screen that should be on, and a 0 for a point that
should be off. The hardware then converts this into the appropriate
signals for the type of display you have. The 1's and 0's get
into the video "frame buffer" through the graphics operations available
on your computer. There are lots of books on computer graphics
with much more information on all this!
Click here to return to the Physics Archives
Update: June 2012