How is soil formed?

          Soil is the upper most surface layer of the earth in which plants grow and on which directly or indirectly, all life depends. It is composed of rocks, minerals, organic matter, water and air. It did not take one or two days for the soil to form but millions of years. Do you know how soil is formed?

          Millions of years ago, soil existed in the form of rocks. Since then weather and other natural forces like wind, rain, snow, water, heat etc. had been interacting with the rocks to break them into smaller fragments. These forces further converted the rock-pieces into sand. Bacteria, carbonic acid and other micro-organisms converted this sand into soil. In course of time bacteria converted the bodies of dead plants and animals also into soil.



          Soil is classified according to its colour, texture, chemical properties and climate. Colours of soil range from yellow and red to black. Soils are also categorized as acidic, alkaline and neutral. Extremely acidic or alkaline soil does not support plants. 





          There are three main types of soil a) Pedalfers - associated with temperature, humid climate, contain iron and aluminium salts, b) pedocalo - associated with low rainfall regions, contain soluable substances such as calcium carbonate and other salts and c) Laterites - tropical red or yellow soils heavily leached and rich in iron and aluminium. Based upon soil classifications, modern farming and plantation are made to yield maximum returns.



          An organic matter called humus is constantly being added to the parent soil. Humus makes the soil more fertile.



          Deep, well developed soil is divided into four layers called horizons. The top layer, where most plants grow, is called the A-horizon or top soil. This layer is rich in organic material and contains some minerals. The next is called B-horizon or sub soil. It is rich in minerals, especially in clay, but with little or no organic matter. Farmers often mix the A-and B-horizons by ploughing. The third is called C-horizon and it is a layer of weathered and shattered rocks. It is called the fragmented rock. It is quite similar to parent soil. The last layer is D-horizon or bed rocks. 


Why do objects appear coloured?

          Do you know why an apple or tomato appears red, the grass green, and the milk white when they are all illuminated by the same sunlight? In fact, the colour of an object depends upon the colour it reflects.

          The sunlight which appears white comprises of seven colours: violet, indigo, blue, green, yellow, orange and red. In sunlight, an apple or tomato appears red because it reflects only the red colour and absorbs the rest.



Grass appears green because it reflects only the green colour and absorbs all other colours present in the sunlight. A white shirt or milk appears white because it reflects all the colours of the sunlight. And a blackboard appears black because it absorbs all the colours of white light and reflects none. To prove this, focus red light on a white shirt and you will see that it becomes red. White objects take the colour of light falling on it. Similarly if we see an apple in red or white light it will appear red but in green or blue light it would appear black. It cannot reflect any other colour but red and, therefore, looks black in any other colour except red or white. This is how the various objects get their colour. 


Which planets have satellites?

          The heavenly bodies that revolve round the sun are called planets. There are nine planets in our solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto. The bodies revolving round these planets are called their ‘satellites’ or ‘moons’.

          Scientific investigations made so far have revealed that all planets do not have satellites. For example, Mercury and Venus do not have any satellite. Earth has 1 satellite - the moon. Mars has 2 satellites and the Jupiter has 16. The number of the moons revolving round Saturn is 24. The Uranus and Neptune have 15 and 6 satellites respectively. Pluto has 1 satellite.



          The size of different satellites is different. There are some satellites which are bigger than moon. The diameter of two satellites of the Mars, Deimos and Phobos, and the outer satellites of the Jupiter, Ganymede and Callisto are as big as Mercury and Mars. The diameters of Titan and Triton - the satellites of Saturn and Neptune are 5150 kms and 2700 kms respectively and more than the diameter of our moon.



          Except Titan, all the satellites have small force of gravity. As such none of them has any atmosphere. Because of low temperature at Titan, it has an atmosphere consisting of methane and hydrogen. But there is no life on this satellite.



          As yet we have not come across any satisfactory theory regarding the origin of the satellites. However, it is believed that their origin is similar to that of our solar system.


How does a currency counting machine work?

          There are thousands of banks in the world where currency notes are counted and packed in the denominations of hundreds. Job of counting and packing is done by a large number of people. The job of counting the currency notes is quite boring. Scientists have developed a machine which automatically counts and packs the currency notes. This machine is a wonder of electronics.

          Working principles of a currency counting machine is shown schematically in the figure. The bundle of notes to be counted is placed on platform P-1. These notes are pushed in the forward direction by a feeding roller R-1. These notes are counted by a sensor S-1. Thereafter the notes pass through the rollers R-2 and R-3 and channel C-1. Through the channel the notes reach the sensor S-2. In case of any error in counting, S-2 will shut the motor automatically and display the mistake. After sensor S-2, rollers R-4 and R-5 pick up the notes and throw them into the slots of the centrifuge roller. These notes are released as they reach the platform P-2 and start stacking upon it. This platform is equipped with another sensor S-3 which indicates whether P-2 is empty or loaded.



           It is a microprocessor based machine and hence its reliability is very high. These machines can not only count currency notes but also the coins. These are portable machines and can be installed anywhere. Nowadays these machines are being used by many banks.


What is a Silicon Chip?

          The microchip or silicon chip has completely changed the colour of the electronic world by providing a new direction to it. It has led to the invention of electronic calculators, personal computers, digital watches, microwave ovens etc.

          The silicon chips are tiny crystals of silicon which contain large number of electronic components. Silicon is the most abundant element on earth as the crust of the earth is largely made of silicon. But silicon is not found in a free state as it is always combined with one or more additional elements. In one sq. cm. chip, about one million electronic components can be squeezed. The size of a chip is smaller than our finger tips. They can be made to carry very small electrical circuits, called microcircuits. These are used in transistor radios, digital watches, calculators and computers. They can be used in small electronic devices as the chips are very small.



          But how is silicon chips made? Silicon chips are made from a single crystal of silicon. Thin wafers of about 0.5 mm thick are sliced from a single crystal. One side of each wafer is first polished and then oxidized in a furnace: The disc is covered with a layer of photo resist material and then exposed to ultraviolet light through the clear sections of a mask. A light sensitive coating is developed and the exposed areas are dissolved away by the solvent. Unexposed areas are not affected so a pattern remains identical to the mask. The exposed areas are etched in hydrofluoric acid. Another solvent removes the resist. In a furnace, the wafer is exposed to chemicals which penetrate the silicon through the oxide gap to make transistors. The process is repeated several times. The wafer is coated with aluminium and a final layer of metals connects the components together. After careful inspection, chips are selected and released for use.



          Nowadays microchips are being used in electronic sewing machines, washing machines, word processors, and so on. 


What is a space suit?


          We know that the atmosphere at the Earth’s surface produces a pressure equal to the weight of a large automobile on each square metre. We do not notice this since it is equal both inside and outside our bodies. But if the air inside a metal pot is, for instance, forced out by boiling water inside it, the pot collapses under this pressure.



          Similarly, an unprotected astronaut in a space flight would not only die by swelling up, but his blood would also start to boil. The temperature at which a liquid boils depends on the atmospheric pressure. At a height of 9 km, water boils at 74°C; and above 19 kms, blood boils below body temperature. At zero pressure, the astronaut’s blood would instantly turn to deadly foam.



          Therefore, keeping these aspects in view, a space suit is specially designed so as to protect an astronaut from the dangers of space during space flights. Space dangers include extreme temperature, hazardous radiations, fast moving particles, vacuum etc.



          Space suit clothing is made of several layers each of which has a specific purpose. One of the inner layers controls the temperature. With the help of this Manned Manoeuvring Unit (MMU), an astronaut can leave the space craft and fly independently. It has the provision for oxygen gas. Each suit has got a primary life support system. It holds enough water and oxygen to enable the astronaut to carry out space walks for several hours. The space suit has the liquid cooling and ventilation system. In fact each suit is made from a number of different pieces. Each piece is made by selecting the sizes. Individual astronaut is given a suit from these so as to fit him.



          One very surprising thing about MMU is its weight. On earth it weighs about 158 kgs but when used in space it makes the astronaut very mobile. This is because of the weightlessness conditions in the space.



          A space suit therefore is a life-saving device for an astronaut.



 


How is the distance of stars from the earth measured?

          The stars which we see shining at night look very attractive and bright. Some stars look brighter than others. This is so because their sizes and distances from the earth are different. These stars are billions of miles away from our earth and shine with their own light. Do you know how the distance of stars form of earth is measured?



          Scientists have evolved a simple technique to measure the distance of the nearby stars. Suppose we want to measure the distance of a particular star ‘C’. We take its photograph from a place ‘A’ on the earth. After six months, the earth is at the position ‘B’, since it is revolving round the sun. We now take another photograph of the same star from the position ‘B’. A comparison of the two photographs will show that ‘AB’ is the diameter of the earth’s orbit round the sun and is equal to 186 million miles. Now the angle ‘ACB’ is measured. With the help of these two figures, the distance of the star ‘C’ is measured. This is known as the method of triangulation.



          Using this technique, the distance of many stars has been measured. The distance of Alpha Centauri from earth has been found to be about 4.35 light years. The distance of the Sirius has been determined to be 8.48 light years. However, this technique is not suitable for measuring the distance of very distant stars. The distance of such stars is determined on the basis of their brightness or colour. The most widely used system for measuring the distance of stars is the two-dimensional classification method developed by J.M.Johnson and W.W. Morgan. This system is based upon photoelectric measurement in three wavelength bands in ultra-violet, blue and yellow (or visual) regions of spectrum. This method is known as UBV system. Scientists have succeeded in measuring the distance of stars as far away as 8 million light years from the earth.





 

How can we test the purity of milk?

             The instrument used to assess the purity of milk is called a ‘lactometer’. It is a cylindrical vessel made by blowing a glass tube. One end of the glass tube is blown in the form of a bulb and filled with mercury. The other end is blown in the form of a thin tube and sealed. For calibration it is dipped in pure milk. The point up to which it sinks in the pure milk is marked ‘M’. After that it is put in water and is marked ‘W’ at the point up to which it sinks in water. It sinks less in milk than in water because milk is denser than water. The portion between ‘M’ and ‘W’ is divided into three parts and marked as 3, 2 and 1 to indicate the level of purity.

              Whenever we want to test the purity of milk, the instrument is put in milk. If it sinks up to the mark ‘M’, the milk is pure. If the milk is not pure, but mixed with water, it would sink to a mark higher than ‘M’. When the instrument stands at the mark 3, the milk is 75% pure. At the mark 2, the purity is only 50%. Mark 1 indicates a purity of 25%.



            Even though lactometer is commonly used to measure the purity of milk, yet, it is not a very reliable instrument. It has been observed that in the case of skimmed milk (denser than pure milk) that the lactometer fails to give the correct assessment of the purity, if the density of the skimmed milk is made equal to that of the pure milk by adding water in an appropriate proportion.


What is Paging Service?

            The 21st century would take people to a world of mechanical solidarity with courtesy from services like paging service, cellular telephone and Internet etc. Having acquainted ourselves with services like cellular telephone and Internet earlier, now let us discuss what paging service is all about.

            Paging is a one-way wireless communication providing instant access to the person being paged. One-way communication means that the subscriber only receives the message and can not communicate back instantly. The subscribers receive messages from anyone with access to a telephone. The modus operandi is as follow: The paging network of a particular region is co-ordinated by a ‘pagers exchange’ or network operator. Subscribers have a paging number assigned exclusively to them by the concerned network operator. The person who wants to send a message to a subscriber rings up the operator and leaves the message with him along with the subscriber’s paging number. Then the operator relays the message to the subscriber either directly or through any other regional operator. The message is then received by a small palm-size device called ‘pager’ kept by the subscriber with himself. An alarm sound from the device alerts the subscriber who then reads the message, flashed on the screen of the device. Some pagers also vibrate to alert the subscriber of an incoming message. The main advantage which a pager provides is that the subscriber receives the message wherever he may be since he carries the wireless device (pager) always with him.



            In India, as of now, the government has issued licenses to private operators to provide paging service to interested people and the number of subscribers is growing fast. As per current estimates, the running cost of a pager for monthly service would be around a couple of hundred rupees and a pager, at the moment, costs about a few thousand rupees. It is now the cheapest and most reliable one-way communication system available in the market today. Although its primary use is to get a message across fast, it has other potential uses such as getting across share market information by the business circles or to have latest cricket scores, for instance. The only demerit is that it provides only one-way communication as the receiver can not communicate back to the caller. 


What is Electronic Mail?

          Electronic mail is a modern method of instant delivery of letters without the involvement of a postman. In this system of mailing, messages are sent with the help of a computer.

          In the electronic mail system a letter or any other document is typed and edited on a computer. It is then sent to the addressee through a computer network in the form of electrical signals. The addressee may be anywhere in the world but he should also have an electronic mail system. The contents of the transmitted letters or documents get displayed on the screen of the computer of the addressee. If he desires, he can get the message printed. If the addressee is absent, the transmitted matters will be automatically stored in the computer’s memory. When he returns the computer will give an indication that some mail is waiting for him.



          With the help of electronic mail system both typed and handwritten matters can be transmitted. Electronic mail is very fast and saves time and paper work but at present it is very costly. It needs a satellite, telephone and cable links with television, voice and computer data telecommunications. The electronic mail system has so far not been feasible for individual households. This system is being used by developed countries on a large scale.



          Email is widely used in Internet Services. It is also connected to other systems in which exchange of Email are being made effectively.



 



 


How are submarines detected under the sea?

           The main device used to detect and locate objects like submarines and torpedoes under the sea water is called ‘sonar’. The word ‘sonar’ is an acronym for ‘sound navigation’ and ranging. This instrument is particularly useful in sea warfare. However, in peace time also, this is used in ships and submarines. It can locate objects at distances ranging from 100 metres up to 10 kms.



           Sonar mainly consists of two parts: the transmitter and the receiver. Both these parts are submerged in the sea water. The transmitter with the help of a transducer produces sound waves of high frequencies (5,000 to 300,000 hertz). These waves are called ultrasonic waves and cannot be heard by human ears. The transmitter transmits these waves in pulses in all the directions. Whenever these pulses strike some object inside the sea water, they get reflected. These reflected waves are received by the receiver. The time taken for the waves to reach the object and come back to the receiver is measured. Half of this time when multiplied by the speed of sound in sea water gives the distance of the object. This instrument contains a display device also, which accurately shows the distance and position of the object. 





           Sonar, however, is not a foolproof system. The sounds produced by some aquatic animals sometimes interfere with its transmissions and can be misleading about the position of the objects. The enemy submarines can be detected by this equipment and thus can be destroyed. These days there are various kinds of sonars being used for studying the objects inside water. Sonars also help in large scale fishing by locating those spots where large groups of fishes are present. Nowadays blue-green laser pulses are also being used for underwater detection of submarines and torpedoes. Laser based devices also work on the echo sounding principle just as a sonar works. 



 


Why can’t we fly like birds?

          An obvious answer to this question is, “We cannot fly like birds because we do not have natural wings”. However, this answer does not explain this question fully because even if we attach artificial wings to our arms we cannot fly. Then how do the birds fly?

          Birds, of course fly with the help of their wings. They have very light frames. Their bones are also light. Moreover, they have air sacs which make them even lighter.



          Their muscles are quite strong in comparison to their body weight. They have a streamlined body which enables them to fly swiftly because air offers less resistance to streamlined objects. With the help of these muscles, they can easily fly with their wings.



          When a bird flaps its wings, it pushes the air down with its wings and rises above. Our bodies are heavier than those of birds. As such we would need enormously big wings. Again we do not have any air sacs and our muscles are not comparatively that strong. Hence we cannot flap the artificial wings.



          The birds with lighter bodies can fly more easily while the heavy birds face difficulties while flying. For example, the cock and peacock cannot fly very high. There are also birds like ostrich and penguin which are even heavier. They cannot fly at all. They can simply run. Thus we too cannot fly like birds even if we attach artificial wings to our arms.



 


What is Internet?


          The rapid progress made in the field of Information Technology has revolutionized the world of communications. The world is gradually becoming a global village as interaction among people all over the world has become more frequent than ever before. The widespread and efficient use of computers in the field of telecommunications has made the world a smaller place to live in. ISD, FAX, Electronic Mail, Paging Service and now Internet - all are the gifts of this revolution. Internet has aroused much interest in recent days as it has become a very powerful medium of communication. But what is Internet and how does it operate?



          Internet is the world’s largest computer network. A computer network is basically a bunch of computers connected together in some way or other. It is just like a radio or TV network that links various radio or TV stations so that they can share a common programme. The major difference is that in TV networks the same information programme is sent to all stations whereas in computer network, each particular message is usually routed to a particular computer. Some computer networks consist of a central computer and a bunch of remote stations that report to it - for example, the centralized railway reservation system which links many terminal counters to a centralized computer. But other networks like the Internet permit any computer on the network to communicate with any other. Actually, the Internet is not really a network; it’s a network of networks - all freely exchanging information.



          Through Internet people from all countries can now share information, ideas, stories, data and opinions - the functions that are now generally carried out by letters, telephones and other modes of communications. It has become the fastest and most reliable way to move or exchange information. For example, during the 1991 Soviet coup, a tiny Internet network provided all the information to the rest of the world when all other communication systems were shut off. Medical researchers all over the world use the Internet to maintain data bases of rapidly changing data.



          The Internet facilities are provided through a large set of different services. Though to mention all the services would make the list exhaustive, some examples can be given. Electronic mail is the most widely used Internet service. Electronic mailing lists enable one to join in group discussions and meet people over the Net. Online conversation, Information retrieval, Bulletin boards and Games and gossip (challenging other players who can be anywhere in the world) are some other kind of Internet services.



          India’s access to the Internet has ushered in a new phase of computer communications in the country. Originally a small electronic community in the American Defence Department as a way for military researchers to contact with each other, Internet is now the world’s largest electronic network.



 


What is a Hydrogen Bomb?

          Soon after the development of the atom bomb in 1945 scientists started developing a more powerful bomb. As a result, they managed to develop another highly destructive bomb called the ‘hydrogen bomb’. The first hydrogen bomb was tested in 1952 by the American scientist Edward Teller and his team. It was a 10 megaton bomb, about 700 times more powerful than the atom bomb dropped in Hiroshima.

          The hydrogen bomb makes use of the phenomenon of ‘nuclear fusion’. In the fusion process, four hydrogen nuclei combine at extremely high temperature to form one helium nucleus. In the fusion reaction tremendous amount of heat energy is liberated. Similar reactions take place in the sun and other stars due to which, they have been producing continuously enormous amounts of heat and light energy. 



  



       The shell of the hydrogen bomb is made of a strong alloy. Two isotopes of hydrogen (deuterium and tritium) are kept inside this cover. One atom bomb is also enclosed in the same shell to initiate the fusion reaction. When the hydrogen bomb is to be exploded, the atom bomb is made to explode first. It produces a temperature of millions of degrees. At this temperature, deuterium and tritium combine together to form a helium nucleus and produce huge quantity of heat. This reaction is completed in one millionth of a second. In fusion, not only the helium nuclei are formed but neutrons are also produced. These neutrons carry out the fission reaction in uranium by which heat is continuously produced to carry out fusion reaction. That is why this bomb is more powerful. For peaceful uses, they can be modified so that the radio activity produced is minimal.



          So far hydrogen bombs have been developed by USA, Russia (former USSR), UK, France and China. Erstwhile USSR tested a hydrogen bomb in 1962 whose power was equivalent to 62 megaton TNT. 


How are valleys formed?


          The wide, broad plains or uneven tracts with gradual slopes between the mountains are called valleys. They are found in the mountains all over the world. Srinagar is one of the beautiful valleys in our country. Do you know how valleys are formed?



          Most of the valleys were formed by rivers. When streams originate on hill top, their water flows down the side of the hill. Because of the steepness of the slope, the river flows very fast and the force of water eats into the hillsides, forming a narrow V-shaped bed. With the passage of time, it becomes U-shaped when the water from other sides joins it and its breadth goes on increasing. Eventually the banks of the river become flat and the floor of the river widens. The area almost becomes like a plain. This is how a valley is formed. It takes thousands of years for its formation.



          Some valleys have been formed by glaciers. Glaciers are slow moving rivers of ice. The ice grinds deeply into the ground and at the same time smoothens out any ridges in its path. The glacier picks up all the rocks and other projections that come in its path, breaks them up and redeposits them smoothly over the ground. This makes the ground smooth and a U-shaped valley comes into existence.



          Sometimes the river changes its direction and thus the river bed becomes dry. The valley formed in this manner is called a dry valley.



          Sometimes when land sinks between two fractures in the earth’s crust, a valley is formed. These valleys are called ‘rift valleys’. The most famous valley of this type is the Great Rift Valley, which extends to more than 5000 km from Syria to East Africa. Narmada, a famous river of India, also flows through a rift valley.



          All the ancient civilizations started in the valleys only.