1 The Medium of Television
From physics we can learn what makes it possible for a set to present a visual image. We can learn how an electron beam, directed toward the surface of a screen on which a luminescent substance has been spread, is made to scan the screen long enough to produce the illusion of a photographic reproduction. Beyond these facts, there are others that need to be learned if one is to understand from first principles the electromagnetic phenomena involved from the moment a camera is directed towards an object to the appearance of its image on a screen in a home. All this we shall either assume is known by the readers or, because it is altogether unnecessary to understand what follows, irrelevant and not called for. The images on the screen are watched by eyes, and one could equally well say that it is necessary to know as much of the phenomena involved in sight as of the phenomena that enable
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