LAWS OF PHOTOELECTRIC EMISSION AND IT'S EXPLANATION IN SIMPLE WAY WITH HELP OF EINSTEIN'S EQUATION

LAWS OF PHOTOELECTRIC EMISSION

1. The photo current is directly proportional  to the intensity of light and is independent of frequency.
2. The kinetic energy of the photo electrons is directly proportional to frequency and is independent of intensity.
3. Photoelectric effect does not happens when the incident frequency is less than a minimum frequency ( threshold frequency )
4. There is no time lag between the incidence of photon and emission of electrons or photoelectric process is an instantaneous. 

Einstein's equation       

 EXPLANATION :

1. According to quantum theory each photon interacts only with  each electron. When the intensity is increases more photons will come and they will interacts with more electrons. This will increase the amount of photo current.
2. According to Einstein's equation  hvo  is constant  then kinetic energy is directly proportional to frequency.
3. We know Einstein's equation. If  v < vo , then kinetic energy becomes negative and it is impossible, in other words photoelectric effect does not happens.
4. According to quantum theory  each photon interact with each electron so different electrons will be interacted with different photons at same instant so there is no time lag between incidence and emission.

DATA COMMUNICATION DEVICES

We know that  inter networking  is the process of connecting two or more networks together so that data transmission between networks may take place. There is possibility that the networks, which are to be connected, are not compatible. In such cases of incompatibility of networks, it is required that a "black box" be inserted at the junction point so that necessary conversions are possible as data packet moves from one network to the other. Such a black box in general is called 'relay'. Relays may connect to or more networks. Bridges and gateways are examples of relays used for this purpose.



BRIDGE

A bridge is a device to link two networks. A bridge is used to link same type of networks (LANs). When a packet (data packet) reaches the bridge, it decides whether it is to be addressed to a node on the other side of the bridge or on the same side. A bridge filters out those packets which are addressed to the same side of the network and passes all other packets which are addressed to some  nodes on the other side of the network.


ROUTER

A router is similar in operation to a bridge, but it can connect two networks with different protocols.  A router may be connecting two networks A and B. A message originating from node 3 of network A may be directed to node 5 of network B. The router checks the node address and the network address and use algorithms to find the best path to reach the destination. Different networks may use different protocols for communication. Therefore some kind of mutual understanding is required for compatibility between the two protocols so that data can be transferred from one network to any other. A router is the device which establishes understanding between the protocols of different networks.


GATEWAY


A gateway is used to connect two networks of different types, it is like a router in the sense that it finds the optimal path for a message directed to a specific node in a different network. In addition, it can convert the message from one code to another. For example, it can convert an e-mail message received in one format into another.

VARIOUS NETWORK CONNECTORS

WHERE DO YOU CAN FIND THE REAL HAPPINESS.

I think all the people in this beautiful planet likes to lead a happy life. But due to different situations in life they couldn't find happy in their life. According to me the right place you can find the happiness is in jesus christ. He is the only one who can make you real happy. In the present world people search for happy and they find their answer in alcohol, drugs.  Doing bad things. Watching bad things etc. This is one of the big mistake that you makes in your life. You may think these things can make you happy but it's not the truth. It's not a joke because these items deliver only a temporary happy for few minutes, Few hours or for few days. After that you may be depressed or feel lonely by thinking that you have done this or that. You may loose your control and your total attitude may change. Another major problem of using drugs and alcohol is that people just start it for fun but later they get addicted to it. It causes lots and lots of problems so it's better to avoid such things. Just remember that these items can't give you the real happiness so as I told before the only place that you can find the real happiness is in jesus christ. So stay always close to him and I'm sure that he will let you to enjoy the real world of peace and happiness.

THE GOD IS GREAT. WE SHOULD LOVE HIM.

The God is great. He created such a beautiful planet earth for us. He provides us what we need. But the people are running to make money by forgetting the God almighty. In the journey of our life we have done many sins by knowing and unknowing but the god have forgiven our sins. He also remember us not to repeat the same mistakes. But what we do.? For our happiness we repeat the same mistakes . I think this  hurts God so we should try to avoid these kind of mistakes. We should love God has much as we could. It is the only way that we can enjoy the real happiness in our life.

PHOTOCELL, IT'S WORKING AND IT'S USES

A photocell is a technological application of the photoelectric effect. It is a device whose electrical properties are affected by light. It also some times called an electric eye. A photocell consists of a semi cylindrical photo sensitive metal plate c (emitter) and a wire loop A (collector) supported in an evacuated glass or quartz bulb. It is connected to the external circuit having a high tension battery B and micro ammeter as shown in the figure.

Sometime instead of the plate  C, a thin layer of photosensitive material is pasted on the inside of the bulb. A part of the bulb is left clean for the light to enter it. When light of suitable wavelength falls on the emitter C, photo electrons are emitted. These photo electrons are drawn to the collector A. Photo current of the order of a few micro ampere can be normally obtained from a photo cell.

A photocell converts a change in intensity of illumination into a change in photo current. This current can be used to operate control systems  and in light measuring devices. A photocell of lead  sulphide sensitive to infrared radiation is used in electric ignition circuits.

In scientific work, photo cells are used whenever it is necessary to measure the the intensity of light. Light meters in photographic cameras make use of photo cells to measure the intensity of incident light. The photocells, inserted in the door light electric circuit, are used as automatic door opener. A person approaching a doorway may interrupt a light beam which is incident on a photocell. The abrupt change id photo current may be used to start a motor which opens the door or rings an alarm. They are used in the control of a counting devices which records every interruption of the light beam caused by a person or object passing across the beam. So photocells help count the person entering an auditorium, provided they enter the hall one by one. They are used for detection of traffic law defaulters: an alarm may be surrounded whenever a beam of (invisible) radiation is intercepted.

In burglar alarm, (invisible) ultraviolet light is continuously  made to fall on a photocell installed at the door. A person entering the door interrupts the beam falling on the photocell. The abrupt change is photo current is used to start  an electric bell ringing. In fire alarm, a number of photocells are installed at suitable places in a building. In the event of breaking out of fire, light radiations fall upon the photocell. This completes the electric circuit through an electric bell or a siren which starts operating as a warning signal.

Photocells are used in the reproduction of sound in motion pictures and in television camera for scanning and telecasting scenes. They are used in industries for detecting minor flaws or holes in metal sheets. 

PARTICLE MODEL OF LIGHT

P a R T i C l E    M o d E l    o F     L i G H t 

Newton's fundamental contributions to mathematics, mechanics, and gravitation often blind us to his deep experimental and theoretical study of light. He made pioneering contributions in the field of optics. He further developed the corpuscular model of light proposed by Descartes. It presumes that light energy is concentrated in tiny particles called corpuscles. He further assumed that corpuscles of light were mass less elastic particles. With his understanding of mechanics, he could come up with a simple model of reflection and refraction. It is a common observation that a ball bouncing from a smooth plane surface obeys the laws of reflection. When this is an elastic  collision, the magnitude of the velocity  remains the same. As the surface is smooth, there is no force acting parallel to the surface, so the component of momentum in this direction also remains the same. Only the component perpendicular to the surface, i.e., the normal component of the momentum, gets reversed in reflection. Newton argued that smooth surfaces like mirrors reflect the corpuscles in a similar manner.

In order to explain the phenomena of refraction. newton postulated that the speed of the corpuscles was greater in water or glass than in air. How ever, later on it was discovered that the speed of light is less in water or glass than in air.

In the field of optics, Newton the experimenter, was greater than Newton the theorist. He himself observed many phenomena, which were difficult to understand in terms of particle nature of light. For example, the colours observed due to a thin film of oil on water. Properly of partial reflection of light is yet another such example. Everyone who looked into the water in a pond sees image of the face in it, but also sees the bottom of the pond. Newton argued that some of the corpuscles, which fall on the water, get reflected and some get transmitted. But the property could distinguish these two kinds of corpuscles ? Newton had to postulate some kind of unpredictable, chance phenomenon, which decided whether an individual corpuscle would be reflected or not. in explaining other phenomena, how ever, the corpuscles were presumed to behave as if they are identical, Such a dilemma does not occur in the wave picture of light. An incoming wave can be divided into two weaker waves at the boundary between air and water.

HISTORICAL NOTE OF DETERMINANTS

The Chinese method of representing the coefficients of the unknown of several linear equations by using rods on a calculating board naturally led to the discovery of simple method of elimination. the arrangement of rods was precisely that of the numbers is determinants. the Chinese, therefore early developed the idea of subtracting   columns and rows as in simplification of a determinant 'Mikami, China, pp 30, 93.

Seki Kowa, the greatest of the Japanese Mathematicians of seventeenth century in his work 'Kai Fukudai no Ho'  in 1683 showed that he had the idea of determinants and of their expansion. But he used this device only in eliminating a quantity from two equations and not  directly in the solution of a set of simultaneous linear equations. 'T. Hayashi, " The Fakudoi and Determinants in Japanese Mathematics," in the proc. of the Tokyo Math. Soc., V,

Vendermonde  was the first to recognize determinants as independent functions. He may be called the formal founder. Laplace (1772), gave general method of expanding a determinant in terms of its complementary minors. In 1773 Lagrange treated determinants of the second and third orders and used them for purpose other than the solution of equations. In 1801, Gauss used determinants in his theory of numbers.


The next contributor was Jacques-Philippe- Marie Binet (1812) who stated the theorem relating to the product of two matrices of m-columns and n-rows, which for the special case of m=n reduces to the multiplication theorem more satisfactory then Binet's 

The greatest contributor to the theory was Carl Gustav Jacob Jacobi, after this the word determinats received its final acceptance.

QUATERNARY PERIOD

THE QUATERNARY PERIOD (1.6 million years ago present) forms the second part of Cenozoic era (65 million years ago present): it has been characterized by altering cold (glacial) and warm (inter glacial) periods. During cold periods, ice sheets and glaciers have formed repeatedly on northern and southern continents. The cold environment in North America and Eurasia, and to a lesser extent in South America and parts of Australia, have caused the migration of many life forms towards the Equator. Only the specialized ice age mammals such as Mammuthus and Coelodonta, with their thick wool and fact insulation, were suited to life in very cold climates. Humans developed throughout the Pleistocene period (1.6 million-10,000 years ago) in Africa and migrated northward into Europe and Asia. Modern humans, Homo sapiens, lived on the cold European continent 30,000 years ago and hunted mammals. The end of the last ice age and the climatic changes that occurred about 10,000 years ago brought extinction to many Pleistocene mammals, but enabled humans to flourish.

TERTIARY PERIOD

Following the demise of the dinosaurs at the end of the cretaceous period, the tertiary period (65-1.6 million years ago), which formed the first part of the Cenozoic era (65 million years ago present), was characterized by a huge expansion of mammal life, Placental mammals nourish  and maintain the young in the mother's uterus; only three orders of placental mammals existed during cretaceous times, compared with 25 orders during the tertiary period. One of these 25 included the first hominid, Australopithecus, which appeared in Africa. By the beginning of the tertiary period, the continents had almost reached their present  position. The  Tethys sea, which had separated the northern continents from Africa and India, began to close up, forming the Mediterranean sea and allowing migration  of terrestrial animals between  Africa and Western Europe. India's collision with Asia led to the formation of the Himalayas. During the middle part of the tertiary period, the forest dwelling and browsing mammals were replaced by mammals such as the horse, better suited to grazing the open savannahs that began to dominate. Repeated cool periods throughout the tertiary period established the Antarctic as an icy island continent. 

GUITARS

G u I T a R s

The guitars is a plucked stringed instruments. There are two types of guitar acoustic and electric. Acoustic guitars have hollow bodies and six or twelve strings. Plucking the strings produces vibrations that are amplified by their hollow bodies. Electric guitars usually have solid bodies and six strings. Pick ups placed under the strings convert their vibration into electric signals that are magnified by an amplifier, and sent to a loud speaker where they are converted into sounds. Electric bass guitars are very similar in structure to electric guitars and produce sound in the same way, but have four strings and play bass notes.

CRETACEOUS PERIOD

The Mesozoic era ended with the cretaceous period, which lasted from 146 to 65 million years ago. During this period, Gondwanaland and Laurasia were breaking up into smaller land masses that more closely resembled those of the modern continents. the climate remained mild and moist but the seasons becomes more marked. Flowering plants, including deciduous trees, replaced many cycads, seed ferns and conifers. Animal species become more varied, with the evolution of new mammals, insects, fish, crustaceans and turtles. Dinosaurs  evolved into a wide variety of species during Cretaceous times; more than half of all known dinosaurs including Iguanodon, Deinonychus, Tyrannosaurus and Hypsilophodon lived during this period. At the end of the Cretaceous period, however dinosaurs become extinct. The reason for this mass extinction is unknown but it is thought to have been caused by claimatic changes due to either a catastropic meteor impact with the Earth or extensive volcanic eruptions.

TRIASSIC PERIOD

The Triassic period (245-208 million years ago)  marked the beginning of what is known as the age of the Dinosaurs ( the Mesozoic era). During this period, the present day continents were massed together, forming one huge continent known as Pangaea. This land mass experienced extremes of climate, with lush green areas around the coast or by lakes and rivers, and arid deserts in the  interior. The only forms of plant life were non flowering plants, such as conifers, ferns, cycads, and ginkgos; flowering plants had not yet evolved. The principle forms of  animal life included primitive amphibians, rhynchosaurs ("beaked lizards"), and primitive crocodilians. Dinosaurs first appeared about 230 million years ago, at the beginning of the  Late Triassic period. The earliest known dinosaurs were the carnivorous (flesh eating) herrerasaurids and staurikosaurids,  such as Herrerasaurus and  Stauriksaurus. Early herbivorous (plant eating) dinosaurs first appeared in Late Triassic times include Plateosaurus and Technosaurus. By the end of the Triassic period, dinosaurs dominated Pangaea, possibly contributing to the extinction of many other reptiles.

CARBONIFEROUS TO PERMIAN PERIODS

The carboniferous period (363-290 million years ago) takes its name from the thick, carbon rich layers now coal that were produced during this period as swampy tropical forests were repeatedly  drowned by shallow seas. The humid climate across northern and equatorial continents throughout Carboniferous times produced the first dense plant cover on Earth. During the early part of this period, the first reptiles appeared. Their development of a waterproof egg with a protective internal structure ended animal life's dependence on an aquatic environment. Towards the end of Carboniferous times, the Earth's continents Laurasia and Gondwanaland collided, resulting in the huge land mass of Pangaea. Glaciers smothered much of the southern hemisphere during the Permian period (290-245 million years ago), covering Antarctica, parts of Australia and much of South America, Africa and India. Ice locked up much of the world's water and large areas of the northern hemisphere experienced a drop in sea level. Away from the poles, deserts and a hot dry climate predominated. As a result of these conditions, the Permian period ended with the greatest mass extinction of life on Earth ever.

PRECAMBRIAN TO DEVONIAN PERIODS

When the Earth formed about 4,600 million years ago, its atmosphere consists of volcanic gases with little oxygen, making it hostile to most forms of life. One large  super continent, Gondwanaland, was situated over the southern polar region, While other smaller continents were spread over the rest of the World. Constant movement of the Earth's crustal plates carried continents across the Earth's surface. The first primitive life forms emerged around 3,400 million years ago in shallow, warm seas. The build up of oxygen began to form a shield of ozone around the Earth, protecting living organisms from the sun's harmful rays and helping to establish an atmosphere in which life could sustain itself. The first vertebrates appeared  about 470 million years ago, during the Ordovician period (510-439 million years ago), the first land plants appeared around 400 million years ago during the Devonian period (409-363 million years ago), and the first land animals about 30 million years later.

THE CHANGING EARTH

The Earth formed from a cloud of dust and gas drifting through space about 4,600 million years ago. Dense minerals sank to the center while lighter ones formed a thin rocky crust. How ever, the first  known life forms bacteria and blue green algae did not appear until about 3,400 million years ago, and it was only about 700 million years ago that more complex plants and animals began to develop. Since then, thousands of animal and plant species have evolved; some, such as the dinosaurs, survived for many million of years, while others died out quickly. The Earth itself is continually changing. Although continents neared their present locations about 50 million years ago, they are still drifting slowly over the planet's surface, and mountain ranges such as the Himalayas which began to form 40 million years ago are continually begin built up and worn away. Climate is also subject to change: the Earth has under gone a series of ice ages interspersed with warmer periods (the most recent glacial period was at its height about 20,000 years ago)

THE FIVE BASIC CONCEPTS OF OOP (OBJECT ORIENTED PROGRAMMING) WITH DEFINITION

The general concepts of OOP are given below.

1. Data abstraction
2. Data encapsulation
3. Modularity
4. Inheritance
5. Polymorphism

Data abstraction :  Abstraction refers to the act of representing essential features without including the background details or explanation.

Data encapsulation:  Placing data and functions together is central idea of object oriented programming. This is known as encapsulation

Modularity:  The act of partitioning a program into individual units is called modularity.

Inheritance: Inheritance is the capability of one class to inherit properties from another class.

Polymorphism: Polymorphism is the ability for a message or data to be processed in more than one form. The same operation differently depending upon the type of data it is working with.

LASER LIGHT

Imagine a crowded market place or a railway platform with people entering a gate and going towards all directions. Their footsteps are random and there is no phase correlation between them. On other hand, think of a large number of soldiers in a regulated march. Their footsteps are very well correlated. See figure here.

This is similar to the difference between light emitted by an ordinary source like a candle or a bulb and that emitted by a laser. The acronym LASER stands for light  Amplification by stimulated Emission of Radiation. Since its development in 1960, it has entered into all areas of science and technology. It has found applications in physics, chemistry, biology, medicine, surgery, engineering, etc. There are low power lasers, with a power of  0.5 mW, called pencil lasers, which serve as pointers. There are also lasers of different power, suitable for delicate surgery of eye or glands in the stomach. Finally, there are lasers which can cut or weld steel.

Light emitted from a source in the form of packets of waves. Light coming out from an ordinary source contains a mixture of many wavelengths. There is also no phase relation between the various waves. There fore, such light, even if it is passed through an aperture, spreads very fast and the beam size increases rapidly with distance. In the case of laser light, the wave length of each packet is almost the same. Also the average length of packet of waves is much larger. This means that there is better phase correlation over a longer duration of time. This results in reducing the divergence of laser beam substantially.

If there are N atoms in a source, each emitting light with intensity I, then the total intensity produced by an ordinary source is proportional to NI, where as in a laser source, it is proportional to NNI (NN means N square). Considering that N is very large, we see that the light from laser can be much stronger than that from an ordinary source.

When astronauts of the Apollo  missions visited the moon, they place a mirror on its surface, facing the Earth. Then scientists on the Earth sent a strong laser beam, which was reflected by the mirror on the moon and received back on the Earth. the size of the reflected laser beam and the time taken for round trip were measured. This allowed a very accurate determination of (a) the extremely small divergence of a laser beam and (b) the distance of the moon from the earth.

FASTER AND SMALLER: THE FUTURE OF COMPUTER TECHNOLOGY

The integrated chip (IC) is at the heart of all computer system. In fact ICs are found in almost  all electrical devices like cars, televisions, CD players, cell phones etc. The miniaturisation that made the modern personal computer possible could never have happened without the IC. ICs are electronic devices that contain many transistors, resistors, capacitors, connecting wires - all in one package. You must have heard of the microprocessor.  The microprocessor is an IC that processes all information in a computer, like keeping track of what keys are pressed, running programmes, games etc. The IC was first invented by Jack Kilky at Texas instruments in 1958 and he was awarded Nobel Prize for this in 2000. ICs are produced on a piece of  semiconductors  crystal (or chip) by a process called photolithography. Thus the entire information technology (IT) industry hinges on semiconductors. Over the years, the complexity of ICs has increased while the size of its features continued to shrink. In the past five decades, a dramatic miniaturisation in computer technology had made modern day computers faster and smaller. In the 1970s, Gordon Moore, co-founder of INTEL, pointed out that the memory capacity of a chip (IC) approximately doubled every one and half years. This is popularly known as Moore's law. The number of transistors per chip has risen exponentially and each year computers are becoming more powerful, yet cheaper than the year before. It is intimated from current trends  that the computers available in 2020 will operate at 40 GHz (40,000 MHz) and would be smaller, more efficient and less expensive than present day computers. The explosive growth in the semiconductors industry and computer technology is best expressed by a famous quote from Gordon Moore: "if the auto industry advanced as rapidly as the semiconductors industry, a Rolls Royce would get half million miles per gallon, and it would be cheaper to throw it away than to park it."

ALBERT EINSTEIN ( 1879 - 1955 )

ALBERT EINSTEIN ( 1879 - 1955 ) Einstein, one of the greatest physicists of all time, was born in Ulm, Germany. In 1905, he  published three path breaking papers. In the first paper, he  introduced the notation of light quanta ( now called photons) and used it to explain the features of photoelectric effect. In second paper, he developed a theory of Brownian motion, confirmed experimentally a few years later and provided a convincing evidence of the atomic picture of matter. The third paper gave birth to the special theory of relativity. In 1916, he  published the general theory of relativity. Some of Einstein,s most significant later contribution's are: the notion of stimulated emission introduced in an alternative derivation of Planck's black body radiation law, static model of the universe which started modern cosmology, quantum statistics of a gas of massive bosons, and a critical analysis of the foundations of quantum mechanics. In 1921, he was awarded the Nobel Prize in physics for his contribution to theoretical physics and the photoelectric effect. 

THOMAS YOUNG ( 1773 - 1829 )

THOMAS YOUNG ( 1773 - 1829 ) English physicist, physician and Egyptologist. Young worked on a wide variety of scientific problems, ranging from the structure of the eye and mechanism of vision to the decipherment of the Rosetta stone. He revived the wave theory of light and recognised that interference phenomena provide proof of the wave properties of light.

CHRISTIAAN HUYGENS ( 1629-1695 )

CHRISTIAAN HUYGENS ( 1629-1695 ) Dutch physicist, astronomer, mathematician and the founder of the wave theory of light. His book, Treatise on light, makes fascinating reading even today. He brilliantly explained the double refraction shown by the mineral calcite in this work in addition to reflection and refraction. He was the first to analyse circular and simple harmonic motion and designed and built improved clocks and telescopes. He discovered the true geometry of Saturn's rings.

EARTH'S MAGNETISM AND DYNAMIC EFFECT

     


 A freely suspended magnetic needle comes to rest pointing approximate north - south direction. This is because of an external magnetic field - the magnetic field of earth. Earth behaves as a magnet whose field is similar to that of a huge bar magnet and is of the order of  10 raised to -5 T.

The source of geomagnetism is not an exact single one. A reasonable guess is that due to the electrical current produced by convective motion of metallic fluids ( consisting mostly of molten iron and nickel) in the outer core of the earth. This is known as the dynamic effect.

TCP/IP ( Transmission Control Protocol/ Internet Protocol)

Computer with the same network communicate with each other using their physical addresses, which are hard coded on the Network Interface Card (NIC) of a computer ( The NIC is a device that is attached to each of the workstations and the server, and helps the workstation establish the all important connection with the network). But these physical addresses can not be used across multiple networks. Different networks have different addresses lengths as well addressing formats. As we know, Internet is a network of many heterogeneous computer networks. This means that physical addressing would not work on the internet. Therefore, the concept of logical addresses is used in the internet to make it a virtual network. This logical address is the 32 bit IP address. However, at the lowest level, computers must still use physical addresses to communicate with computers on the same networks. Therefore we need a mechanism to convert a logical IP address to a physical address before the actual transmission can take place over a local network.

The TCP/IP  suite of communication protocols makes the internet a worldwide network of computers networks. Since TCP/IP  software is always the same across all computers connected to the internet, we can connect different computers running different operating systems, or better yet, different networks themselves.

TCP/IP  is a layered set of protocols. In order to understand what this means, it is useful to took at an example. A typical situation is sending mail, first, there is a protocol for mail. This defines a set of commands which one machine sends to another,  e.g., commands to specify who the sender of message is, whom iti s being sent to, and then the text of the message. However, this protocol assumes that there is a way to communicate reliably between the two computers. Mail, like other application protocols, simply defines a set of commands and messages to be sent. It is designed to be used together with TCP and IP . TCP is responsible for making sure that the commands get through to the other end. It keeps track of what sent, and retransmits anything that did not get through. Generally, TCP/IP applications use 4 layers :

1. An application protocol such as mail.
2. A protocol such as TCP that provides services needed by many applications
3. IP, which provides the basic service of getting datagrams (a datagram is a collection of the data that is sent as a single message) to their destination.
4. The protocols needed to manage a specific physical medium.

CITIZENS OF THE SEA

From Norway to New Zealand, from the frigid waters of the polar areas to the warm waters of the tropic, and everywhere in between, our seas and oceans teem with marine citizens that  prey, play, fight, survive, give birth in the water and continue the fascinating cycle of marine life.

Many fascinating creatures call the marine kingdom their home. One such creature is the Seahorse- the only animal species in which the male bears the unborn young! Some other interesting inhabitants of the sea are the Mimic octopus that changes its colour and shape in the blink of an eye and the leafy sea dragon that look like a plant! Whales and Dolphins are among the ocean's most intelligent citizens, while Loggerhead turtles, which travel 6000 km across the world's largest ocean braving hungry hammerhead sharks and other troubles to give birth to their young ones, are among its most persevering dwellers.

Some inhabitants of the aqua world have few interesting tricks up their sleeves to lure their prey. One such is the angler fish that lives in the dark, murky depths of the Atlantic and the Antarctic ocean. This angry looking fish swims around with its natural bait-a fleshy lobe tipped with luminous flesh protruding above its mouth! When any curious creatures comes to investigate this strange light glowing in the dark depths of the ocean, the angler fish quickly swallows it! other fascinating creatures include those that pump up and some that glow! When frightened the Puffer fish puffs up to a large ball several times ins normal size! A wonderful glow in the dark creature is the tiny Sea firefly that inhabits the coastal waters of Japan. These amazing creatures were harvested by the Japanese during the World War 2 to aid soldiers in reading maps and messages at night. Another interesting creature called the Flashlight fish has cheeks that glow! Marine creatures vary in size from tiny microscopic organisms to the Blue whale the largest animal on the planet.

The planet's first life form was born in the oceans. Not surprisingly, Oceans are home to about 80% of all life on Earth. Oceans are a treasure trove of life, and what makes them a world worth exploring and preserving is the astonishing diversity and the beauty of the citizens that call it home.

CHARLES AUGUSTIN de COULOMB

French  physicist, best known as for the formulation of Coulomb's law, Which states  that the force between two electrical charges is proportional to the product of the charges and inversely proportional to the square of the distance between them. Coulombic force is one of the principle forces involved in atomic interactions.

Coulomb developed his law as an outgrowth of his attempt to investigate the law of electrical repulsions  as stated by Joseph Priestly of England. To this end he invented sensitive apparatus to measure the electrical forces involved in Priestly's law and published his findings in 1785-89. He also established the inverse square law of attraction and repulsion of unlike and like magnetic poles, which become the basis for the mathematical theory of magnetic forces developed by Simeon- Denis Poission. The coulomb, a unit of electric charge, was named after Coulomb in his honour.

SURFACE ENERGY OF LIQUID

The molecules of a liquid are in a state of random motion inside the liquid. A molecule is attracted by other molecules lying within a range of  molecular force. A sphere of radius equal to the range of molecular force is called Sphere of molecular influence. The molecule at the centre of molecular influence is attracted equally in all the directions by all other molecules in the sphere.


For a molecule A, well inside the liquid, the forces of attraction on the molecule are equal in all directions. Hence net force on it is zero. consider a molecule B near the surface. In this case the sphere of molecular influence is partially outside the liquid. But the molecules within the liquid lying in the molecular influence attract the molecule B. So there is a net downward force.

Consider another molecule C on the surface of liquid. Half of the sphere of influence is outside the liquid. Hence the downward force on molecule is maximum. Thus when a molecule comes to the surface , it is doing work to over come this downward pull. The work done resides as potential energy in the molecule on the surface.

Thus  molecules on the surface of liquid have  potential energy. This energy is called the surface energy. To increase the area of a liquid, work has to be done. Thus energy is required to increase the surface area. The energy required to increase unit area of the surface is called the surface energy.

KEPLER'S LAWS OF PLANETARY MOTION

In 1543 Nicolaus Copernicus stated that all planets move around the sun in circular orbits with the sun at the center. But Johannes Kepler (1571-1630) discarded this theory and proposed the elliptical orbits for the planetary motion. he formulated three laws known as Kepler's law of planetary motion.




1)  KEPLER'S FIRST LAW (LAW OF ELLIPTICAL ORBIT)

       Every planet revolves round the sun in elliptical orbits, with the sun at one of the foci.     




2)   KEPLER'S SECOND  LAW ( LAW OD EQUAL AREA)

       The line joining the sun and the planet sweeps out equal areas in equal intervals of time.  i.e., the areal velocity swept by the radius vector of ellipse is a constant.




3)   KEPLER'S THIRD LAW ( HARMONIC LAW)

      The square of the time period of the revolution of planet around the sun is directly proportional to the cube of the mean distance between the sun and planet.

FORCE AND MOTION

Forces are pushes or pulls that change the motion of objects. To make a stationary object move, or a moving object stop, a force is needed. A force is also required to change the speed or direction of an object. This change in speed or direction is known as acceleration. Acceleration depends on the size (magnitude) of the force and on the mass of the object. The effects of forces were first summarized by Isaac Newton in his three laws of motion. the international unit of force, named after him, is known as newton (N), which is approximately equal to the weight of one apple. Gravity-the force attraction between any two masses can be measured using newton meter (spring balance). Forces are put to useful effect in machines. A simple machine, such as a wheel and axle, is a device that changes the size or direction of an applied force. It allows an applied force (the effort) to produce another force (the load). A lever uses a bar that turns on a fulcrum to exert force. In all simple machines, there is a relationship between force and distance. A small force (in a compound pulley, for instance) moves through a large distance to lift a heavy object a small distance. This is called the Law of simple Machines.

VAN DE GRAAFF GENERATOR, ITS PRINCIPLE,CONSTRUCTION AND WORKING.

V a N      d E     G r A a F f     G E n E r a T O r

A Van de Graaff  generator is a device designed to create static electricity and make it available for experimentation.
  
                      The American physicist Dr. Robert Jemison Van de Graaff invented the Van de Graaff generator in 1931. The device
has the ability produce extremely high voltages as high as 20 million volts. Van de Graaff invented the generator to supply the high energy needed  for early particle accelerators. these accelerators are known as atom smashers because they accelerate the sub-atomic particles to very high speeds and then "smashed" them into the target atoms. The resulting collisions created other subatomic particles and high energy radiation such as X-rays. The ability to create these high-energy collisions in the foundation of particle and nuclear physics.


PRINCIPLE:

The Van de Graaff generator works on the following two principles.

1. Discharging action of sharp points i.e., electric discharge takes place in air or gases readily at pointed conductors.
2. If the charged conductor is brought into internal contact with a hollow conductor , all of its charge transfers to the surface of the hollow conductor  no matter how high the potential of the latter may be.

CONSTRUCTION:

M- a large spherical conducting shell is supported at a height several meters from the ground on an insulator column.

B- an insulating belt wound around two pulleys P1 and P2, this belt is moving continuously by a driven motor at constant speed.

C1,C2- sharply pointed combs close to the belt near its bottom and top, C1 has given 10kV by a high-tension battery (HT) and termed as spray comb and C2 is connected to spherical shell and termed as collector comb.

WORKING:

The high electric field at the pointed end comb C1 ionises the air near them. The +ve charges in air are repelled and got deposited on the belt through a corona discharge. The charges are carried upto C2. A similar corona discharge takes place at C2 and the charges are finally transferred to the shell M. The charge spread over uniformly on the outer surface of M raising its potential to few million volts.

FTP (File Transfer Protocol) AND IT'S ADVANTAGES

FTP is a convention or set of rules used for transferring files from one computer (or network) to another computer (or network). Thus FTP allows copying of files from a remote server to our own computer and transferring files from our computer to some remote computer. Using FTP a user can log on to a remote computer by giving the address of the host computer.

Besides managing the access control and file transfers, FTP also deals with protection given to a file. Protection may not be given to a file if it is assumed that all the clients are trustworthy. Whenever the clients make requests, the server provides the requested files as they are.

A second alternative is to assign a password to each authorized user. The server, before giving access to any file, will check the password of the client and process his/her request only if the password is valid. A third alternative is assign a password to the files. The passwords assigned for files provide different access rights such as read only, modification and full control.


ADVANTAGES OF FTP :

• Useful for transferring files from one network in an organization to another.
• Geographically separated groups working on a common project may co-operate and co-ordinate with each other.
• Most useful way of sharing information and resources over WANs like internet.

 

URL (Universal Resource Locator)

The function of the web server hardware and software is to store the web pages and locate and transmit them to a client computer as and when requests for the web pages come in. When we want to download a website, its address is to be specified at the concerned prompt in the browser program. the web site address is called Universal Resource Locator (URL), which is the address of the home page of the website installed on the web server. There is standard format for the web sited address. It has generally  three parts (eg  www.abcd.com) where www is based on the HTTP, the recent addition to the TCP/IP protocol suite; abcd represents the name of the site; and com is the domain name that describes organizational or geographical realities like com, org,  in, au, etc

RADIO WAVES

R a D I o    W a V E s


Radio waves belongs to the unguided media and they are of different frequencies ranging from 3 KHz to 300 KHz. The picture below shows the spectrum of the radio communication band.

• Very Low Frequency (VLF) waves propagate s surface waves, usually through air, but sometimes through water also. They are usually used for long rang radio navigation and submarine communication.

• Low Frequency (LF) waves also propagate as surface waves and these are used for long range radio navigation or navigation locators.

• Middle Frequency (MF) waves reply on line of sight antennas to increase and control absorption problems. These waves are used for  Am radio, radio direction finding and emergency frequencies.

•  High Frequency (HF) waves are used for amateur radio, international broadcasting, military communication, telephone, telegraph and facsimile communication.
• Very High Frequency (VHF) waves use line of sight propagation and are used for VHF television, FM radio, aircraft AM radio and aircraft navigation.

• Ultra High Frequency (UHF) waves use fine of sight propagation and they are used for television, mobile phone, cellular radio, paging and micro wave links.

• Super High Frequency (SHF) waves are transmitted as either line of sight or into space. They are used foe terrestrial and satellite microwave and radar communication.

• Extremely High Frequency (EHF) waves are transmitted into space, and are used for scientific applications such as radar, satellite and experimental communication.

WEB PAGE

W e B    P a g E



A web page is a simple text file that contains not only text but also a set of HTML (Hyper Text Markup Language ) tags that describe how the text should be  formatted when a browser displays it on the screen. The tags are simple instructions that tell the web browser how the page should look when it is displayed. The tags tell the browser to do things like  change the font size or colour or arrange things in columns. A web page can contain, text, graphics images or even animated graphics. the web pages are created with the HTML language and stored in a computer file having .html or .htm extension in the file name. The extension identifies the file as an HTML file.

MOUNTAIN BUILDING

M o U N t A i N     B u i L D i n G

The process involved n mountain building-termed orogenesis  occur as a result of the movement of the Earth's crustal plates. There are three main types of mountains: volcanic mountains, fold mountains and block mountains. most volcanic mountains have been formed along plate boundaries where plates have come together or  moved apart and lava and other debris have been ejected onto the Earth's surface. The lava and debris may have built up to form a dome around the vent of a volcano. Fold mountains are formed where plates push together and cause the rock to buckle upwards. Where oceanic crust meets meets less dense continental crust, the oceanic crust id forced under the continental crust. The continental crust is buckled by the impact. This is how folded mountain ranges, such as the Appalachian mountains in North America, were formed. Fold mountains are also formed where two areas of continental crust meet. The Himalayas, for example, began to form when India collided with Asia, buckling the sediments and parts of the oceanic crust between them. block mountains are formed when a block of land is up lifted between two faults as a result of compression or tension in the Earth's crust. Often, the movement along faults has taken place gradually over millions of years. How ever, two plates may cause an earthquake by suddenly sliding past each other along a fault line.

WHO INVENTED THE SAFETY PIN...............?

S a F E t y     P i N

The  safety pin was the invention of  WALTER HUNT.  HUNT  was a mechanic from New York, whose other inventions include a forerunner of the Winchester repeating rifle, a successful flax spinner, knife sharpener, streetcar bell, hard coal burning stove, artificial stone, road sweeping machinery, velocipedes, ice ploughs and mail making machinery.

In 1834, Walter Hunt built American's first sewing machine, which was also the first eye pointed needle sewing machine. He later lost interest in patenting his sewing machine, because he believed the invention would cause unemployment.

The safety pin was invented while Walter Hunt was twisting a piece of wire, trying to think of something that would help him pay off a fifteen dollar debt. On April 10, 1849, the safety pin was patented. Walter Hunt also thought little of his safety pin as an invention and soon sold the patent for four hundred dollars.

HOT AIR BALLOONS AND ITS PRINCIPLE

 H o T   A i R   B A L L o O n S

Hot air balloons are the oldest and most successful human carrying flight technology. The first balloons worked on the principle that when air is heated, it rises. A hot air balloon consists of a bag called the envelope that is capable of containing heated air. Suspended beneath is a basket which carries passengers and usually, a source of heat (mostly an open flame). Most balloons today use hot air made by burning propane gas. Soon after the first hot air flights, people realized that the gas hydrogen, which is almost fifteen times lighter than air, can be used instead . Filled with hot air or gas that is lighter than the surrounding atmosphere, a balloon travels by moving wind. Since the  wind direction changes with the altitude, the pilot navigates the balloon's direction by controlling the altitude, either by heating the air or by releasing ballasts. 

FLYING MACHINE

F L y I N g     M a C H i n E

On 17 December 1903 in an  American town called Kitty Hawk, two bicycle mechanics changed the World forever- they flew an airplane! On that historic day, the two mechanics, Orville and Wilbur Wright  made the World's first sustained, powered and controlled  flights in an airplane. The two were brothers who with their first flight marked the birth of modern aviation.

The term  'aviation' relates to the activities involved in the design , development, production, operation and use of aircraft. An aircraft is a vehicle capable of flying by being supported by air. It include fixed wing and rotary wing types (eg; helicopter), parachutes, as well as lighter than aircraft such as hot air balloons and air ships.

The 'Flyer" flown by the wright brothers on 17 December 1903 was 6.4 meters in length and flew at nearly 11 kilometers per hour (kph). In just over hundred years, mankind has bettered the record. For example, a Boeing 747, one of the World's most recognizable aircraft, in 100 feet longer than the Flyer's  first flight! Another  example is the Euro fighter typhoon. It is one of the World's most advanced new generation aircraft. It can travel at the speed of 2125 kph and takes just 2.5 minutes to reach a height of 35,000 feet. Similarly, aeroplanes have developed from rickety biplanes to the Airbus A380, the largest jetliner ever built. This giant plane has 22 wheels and its wingspan is as wide as the length of a football pitch!

An aircraft is an amazing invention through which mankind has overcome the pull of gravity that keeps most of the creatures tied to the ground. It has made possible for us to girdle the globe like birds, fly high and low, at great speed and even perform aerobatics and air shows with extraordinary precision and control. This is why an aircraft is not just a machine capable of flight, but also a source of joy and inspiration.