How do artificial satellites work?


Artificial Satellites



Artificial satellites send signals. There are many different kinds of signals they send. Each carries a different type of information.



Some artificial satellites send their signals to radios, telephones, and television sets. These are called communications satellites. Ships, aircraft, and even some cars use navigation satellites to work out their location on Earth. Weather satellites take pictures of the movements of the clouds. Scientific research satellites send information about the universe. Scientists can use an earth observation satellite to look at Earth and find heavily polluted areas or damaged forests. Military satellites can send signals about the movement of missiles, ships, and soldiers.



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How do Telescopes work?


Telescopes make distant objects look bigger. Two main types of telescopes are refracting telescopes and reflecting telescopes.



A refracting telescope gathers light from a distant object and focuses it through two lenses. It has one big lens in front and a smaller lens you look through. The lens at the front usually has a bulge on both sides. It is thick in the middle and thin around the edges. This lens collects the light from a distant planet or star and forms an image of it in the telescope tube. The other lens, called the eyepiece, is like a very powerful magnifying glass. It makes things look much bigger.



A reflecting telescope uses a large mirror to collect the light, instead of a lens. The mirror is at the bottom end of the tube. The light from a star goes straight down the tube and strikes the mirror. Then the light is reflected up the tube. A smaller mirror reflects the collected light. The light comes out through a hole in the side of the tube, where the eyepiece is.



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Can you tell how computers work?



All computers work in basically the same way. They follow a set of instructions called a program that enables them to do calculations on information fed into them.



This process produces a result that is used in some way. The great advantage of computers over other machines is that the program can be changed, so that a computer can be given a wide variety of tasks to perform.



Computers consist of four main units – an input unit, a central processing unit is at the centre of operations and generally consists of a microchip located in the computer case. It controls the operations of all other units, which may be part of the computer or connected to it.



The input unit is used to feed information or data into the computer. It is usually a keyboard, but it may also be a light pen that interacts with a computer screen, or simpler devices such as a joystick, a mouse or a bar-code reader. The keyboard is also used to write programs.



The central processing unit first passes the information to the internal memory, where it is held temporarily. The program is also held in the memory, and the processing unit follows the program to produce the results. These go to the output unit, which is usually a video screen or printer, or they may be sent along telephone lines to other computers.



The computer also has an external memory unit such as disc drive that takes programs and data from the internal memory and records them for use at a later date.



 



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How computers are used in industry?



The electronic computer is used in many fields of activity and is extremely valuable in doing complicated work accurately and quickly. It has removed much of the drudgery from such routine tasks as telephone se wonderful machines work? We can see in the simple example of checking the stocks held by a warehouse.



In large scale industries it costs a great deal of money to keep a large number of goods in store. Nevertheless a company must always know how many goods it has at a given time in case it runs out of any item. So there must always be a reserve level below which stocks must not go. When that level is reached the company orders more goods to be delivered.



One way of keeping a check is to use a punched-card system. Each article which is delivered to the warehouse has its own card punched with required information which may relate to style, colour, price, size or other relevant details, and this is fed into computer.



When the article is sold and leaves the warehouse the computer is fed with this information too. At any time the computer can show exactly how many of those articles are in stock and if the stocks have to be replenished. The computer does this job with great speed and accuracy and can give an account of exactly how many articles of many different types are in stock.



The initial effect of computers is as an efficient means of performing complicated or routine tasks. In the long term, however, they will make new and different activities possible for instance, education and many occupations will be greatly affected as methods of storing and retrieving vast quantities of information are further developed.



 



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How radar works?



We have all at one time or another heard the echo of our own voice. An echo is caused by sound waves being bounced back from a solid obstacle, rather like a rubber ball bouncing off a wall. The same thing happens to radio waves which are sent out by a powerful transmitter. When the waves collide with a solid object they bounce back and can be picked up by a receiving set which is usually located at the same place as the transmitter. Since the speed of these waves is known we can tell how far away the obstacle is by calculating how long the waves take to cover the distance. This is how radar works.



The word ‘radar’ is an abbreviated form of the name ‘radio detection and ranging’. Radar is now used everywhere’ at airports, missile bases, space centers for following and tracking satellites and on ships and tracking satellites and on ships and aircraft for automatic navigation. A simple form of radar is used by police to detect speeding vehicles.



 



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