Television Screen

The blue-emitting component of most television screens and computer terminals is another sulfide, ZnS Ag,Al. Although rare-earth activated blue-emitting phosphors ZnS Tm " and Sr (P0 2d-Eu (30) have also been evaluated for this appHcation, the search for a good blue phosphor that does not saturate at high current densities and maintains weU continues. 

Phosphorescent pigments are used in military appHcations, plastics, and paints. Zinc sulfide doped with Ag" (blue) cations, or with Cu" (green) cations are important pigments for the production of color television screens. Phosphorescent sulfide pigments are produced in the United States by Radium Corp. and by Conrad Precision Ind., Inc. 

X-ray fluoroscopy is used for direct on-line examination. A fluorescent screen is used to convert x-ray photons into visible light photons. A television camera receives the visible image and displays it on a television screen (see Fig. 19). This type of system is used for security screening of carry-on luggage at airports. 

Figure 1,8, for example, plots the probability that a cell has value 1 at time t4-l - labeled Pt+i - versus the probability that a cell had value 1 at time t -labeled Pt - for a particular four dimensional cellular automaton rule. The rule itself is unimportant, as there are many rules that display essentially the same kind of behavior. The point is that while the behavior of this rule is locally featureless - its space-time diagram would look like noise on a television screen - the global density of cells with value 1 jumps around in quasi-periodic fashion. We emphasize that this quasi-periodicity is a global property of the system, and that no evidence for this kind of behavior is apparent in the local dynamics. 

Thomsons picture of the atom emerged from his work with cathode ray tubes. It was a milestone on the road to understanding atomic structure. But it was not the only major advance to come out of cathode ray experiments. Almost every television set in existence today is a cathode ray tube. The electrons stream from the cathode and are deflected by electromagnetic coils guided by signals from the television station. When an electron hits the televisions screen, which is coated with a phosphorescent material, it produces a dot of color. The dots form the picture you see on the screen. 

Marketers are finding a positive role for anti-microbial compounds in areas which have not been seen before. Recent product introductions accompanied by major promotions by Savlon for First Aid-Hand Hygiene Liquid Gel with claims such as kills 99.99% of germs in 15 seconds . The main actives are ethanol, Triclosan and propylene glycol. Another major promotion from Dettol on Anti-septic properties is currently on our television screens, creating a positive image for use of these ingredients, which could only help this industry. 

The entire CRT industry is based on the quality and reproducibility of the phosphors used. As stated earlier the phosphors used for the different kinds of CRT displays are constantly being researched and improved. For high-definition television screens the phosphors must be prepared with great control over powder morphology and particle size (see Section 9.15.4.2.1). 

The properties of modern electronic, optoelectronic, photonic, and magnetic devices provide another story of great science that has affected most of humankind. Electronic devices require special materials materials that emit light when struck by a beam of electrons for use in television screens and computer monitors, materials to make the semiconductors that are the heart of electronic and microelectronic circuits, and materials that are used in magnetic memory storage devices for computers. 

Some oxide-type minerals have been found to luminesce when irradiated. A simple example is ruby (aluminium oxide with chromium activator), which emits bright-red light. The phosphors are incorporated into colour television screens to emit the colours blue (silver-activated zinc sulphide), green (manganese-activated zinc orthosilicate), and red (europium-activated yttrium vanadate). 

While experimenting with cathode ray tubes (similar to television screens of the 1950s), Wilhelm Konrad Roentgen (1845-1923) discovered an unfamiliar type of radiation. He named these X-rays , using X to signify the unknown. ... 

Zinc sulfide (ZnS) is used as a pigment and to make white glass, rubber, and plastics. It is an ingredient in pesticides, luminous paints, and X-ray and television screens. 

Every day of our lives we run across LCs. They are commonly found in computer monitors, digital clocks, television screens, and other read-out devices. 

A phosphor commonly used on television screens is ZnS doped with Cu. This is much more efficient at transferring energy to the impurity sites for emission than are the phosphors based on phosphates as host. ZnS is a semiconductor. Suggest a reason for the efficiency of transfer in this solid. 

Both types of europium ion are incorporated into the phosphors used in colour television screens and computer monitors. Phosphors are substances that emit light when struck by a beam of electrons. The electron beam stimulates electrons in the atomic constituents of the phosphor into states of greater energy, from which they decay back to their initial state by radiating away the excess energy as visible light. 

The photocurrent can be measured with a galvanometer or recorded on the television screen. 

Phosphors for cathode-ray tubes, television screens, monitor screens, radar screens, and oscilloscopes are tested under electron excitation. Electron energy and density should be similar to the conditions of the tube in which the screen will be used. The phosphors are sedimented or brushed onto light-permeable screens and coated with an evaporated aluminum coating to dissipate charge. The luminescence brightness and color of the emitted light are measured with optical instruments such as photomultipliers or spectrophotometers. 

In what sense is a color computer monitor or television screen similar to our view of matter Place a drop (and only a drop) of water on your computer monitor or television screen for a closer look. 

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