History of television

The invention of the cathode ray tube in 1897 by Ferdinand Braun quickly made possible the technology that we call television. Indeed, by 1907, the cathode ray tube was supplying television images. Within 50 years, television had become a dominant form of entertainment and an important way to acquire information. This remains true today, as an average individual usually spends between two and five hours each day watching television. The name television means distance seeing. Television, or TV, is the technology used to transmit pictures with sound using radio frequency and microwave signals or closed-circuit connections. Television operates on two principles that underlie how the human brain perceives the visual world.

First, if an image is divided into a group of very small colored dots (called pixels) the brain is able to reassemble the individual dots to produce a meaningful image. Second, if a moving image is divided into a series of pictures, with each picture displaying a successive part of the overall sequence, the brain can put all the images together to form a single flowing image. The technology of the television (as well as computers) utilizes these two features of the brain to present images. The dominant basis of the technology is still the cathode ray tube. The cathode ray tube (CRT) is a vacuum tube containing one or more electron guns (a source of electrons or electron emitter) and a fluorescent screen used to view images.

It has a means to accelerate and deflect the electron beam(s) onto the screen to create the images. The images may represent electrical waveforms (oscilloscope), pictures (television, computer monitor), radar targets or others. CRTs have also been used as memory devices, in which case the visible light emitted from the fluorescent material (if any) is not intended to have significant meaning to a visual observer (though the visible pattern on the tube face may cryptically represent the stored data). The CRT uses an evacuated glass envelope which is large, deep (i.e. long from front screen face to rear end), fairly heavy, and relatively fragile. As a matter of safety, the face is typically made of thick lead glass so as to be highly shatter resistant and to block most X-ray emissions, particularly if the CRT is used in a consumer product.

The vacuum level inside the tube is high vacuum on the order of 0.01 Pa to133 nPa. In television sets and computer monitors, the entire front area of the tube is scanned repetitively and systematically in a fixed pattern called a raster. An image is produced by controlling the intensity of each of the three electron beams, one for each additive primary color (red, green, and blue) with a video signal as a reference. In all modern CRT monitors and televisions, the beams are bent by magnetic deflection, a varying magnetic field generated by coils and driven by electronic circuits around the neck of the tube, although electrostatic deflection is commonly used in oscilloscopes, a type of diagnostic instrument.

Plasma televisions do not have a cathode ray tube. Thus, the screen can be very thin. Typically television screens are about 6 in (15 cm) thick. This allows the screen to be hung from a wall. In a plasma television, fluorescent lights are present instead of phosphors. Red, green, and blue fluorescent lights enable a spectrum of colors to be produced, in much the same way as with conventional television. Each fluorescent light contains a gas called plasma. Plasma consists of electrically charged atoms (ions) and electrons (negative in charge). When an electrical signal encounters plasma, the added energy starts a process where the particles bump into one another. This bump releases a form of energy called a photon. The release of ultraviolet photons causes a reaction with phosphor material, which then glows.

II. Spell and transcribe the following words:

cathode, ray, emission, image, circuit, fluorescent, oscilloscope, generated.

III. Find in Text Eleven equivalents for the following words and word combinations:

сделать возможным, электроннолучевая трубка, передавать картинки и звук, цель для радара, работать по принципу, лежать в основе, составить отдельное изображение, экран, светиться, сохраняемые данные, тоновые точки, особенности, электронный прожектор, излучатель, катушка, ускорять электронный луч, растр, ударяться друг о друга, небъющийся, экран (кинескопа),горловина трубки, удалённый конец, свинцовое стекло, управлять интенсивностью, очень тонкий, последующая часть общей последовательности.