Everyday Science Notes
 

[B]Introduction [/B]

1-Nature of Science;
2-Brief History of Science with special reference to contribution of Muslims in the evolution and development of science:
3-Impact of science on society.

[B]2. The Physical Sciences [/B]

4.Universe,
5. Galaxy,
6. Solar system,
7. Sun,
8. Earth,
9.Minerals
10. Solar and Lunar Eclipses ;
11. Day and Night and their variation ;
12. Energy
13.sources and resources of Energy ;
14. Energy conservation ;
15. Ceramics ;
16. Plastics ;
17.Semiconductors ;
18. Radio ;
19.Television ;
20. Telephones ;
21. Camera ;
22.Laser,
23. Microscope.
24.Computers,
25. Satellites ;
26. Antibiotics,
27.Vaccines,
28.Fertilizers,
29.Pesticides.
30.Microoven

[B]1.NATURE OF SCIENCE:[/B]

Definition:
Science can be defined as study
"mainly concerned with the phenomenan of physical universe any or all of natural sciences or biological sciences."
or
Science as the "the field of study which attempts to describe and understand the nature of the universe in whole or part."

Science is the faculty to reason out the how and why of the things as they occur in the phenomenal world or the objective world..Basically science is the study of laws of nature and man has developed science by observing.Infact this subject has completely transformed our power over nature and the world outlook.Development of the modern technology is directly the outcome of the development of modern science.Without the scientific revolution the industrial revolution would not have been possible.

It has raised the human activity level by signifiacnt observations in the various fields of human existence.Whether its the exploration of human health,industrial progress,agrarian developments and modern communication technologies,the benefits gained from this major subject are enormous.Infact it would not be wrong to say that we are living in the age of science and is a dominant factor in our day to day existence.

[B]2.CONTRIBUTIONS OF MUSLIM SCIENTISTS:[/B]

[B]MUHAMMAD BIN MUSA AL KHWARZIMI:[/B]

Made lasting contributions in the fields of Mathematics,Astronomy,Music,Geography and History.He composed the oldest works on Arithmetic and on Algebra.The oldest Mathematic book composed by him is "Kitab ul jama wat tafriq"
He is the first person who used zero and wrote"Hisab ul jabr Wal Muqabla" which is conceived to be an outstanding work on the subject which included analytical solutions of linear and quadratic equations.
In the field of Astronomy he compiled his own tables which formed the basis of later astronomical pursuits in both East and West.
He also contributed in the field of geographical science by writing a noteworthy book KItab ul surat al ard. in Arabic.
His book " kitab al Tarik" is also a memorable work regarding history.

[B]AL BERUNI:[/B]

Born in Afghanistan Beruni made original an important contributions to science.He is conceived to be the most prominent scientists of the Islamic world who wrote around 150 books on various signifiacnt subjects concerning human existence.These subjects include Mathematics,History,Archeology,Biology,Geology,Chem istry ,Religion etc.
He discussed the behaviour of earth,moon,and planets in his book "Qanoon Almasudi" which is also considered as an outstanding astronimical encyclopedia.He also discovered seven differnt ways of finding the directions of north and south and discovered mathematical technques to determine exactly the beginnig of the seasons.
Another noteable discovery he made was that the speed of light is faster than sound .His wide range of scientific knowledge is also revealed through his books" kitab al saidana" and "kitab al jawahar" dealing with medicine and the types of gems their gravity respectively.
He was a prolific writer whose works showed his verstality as a scientist.


[B]AL RAZI:[/B]

The famous philosopher and a noteable surgeon of the Muslim world,Zakriya Al Razi was born in Ray near modern Theran Iran.His eagerness for knowledge lead him to the study of Alchemyand Chemistry,philosophy,logic ,Mathematics and Physics.He was a pioneer in many areas of medicine and treatment of health sciences in general,and in particular he worked alot in the fields of paeditrics,obsterics and opthalmology.
Al razi was the first person to introduce the use of Alcohal for medical purposes and opium for the objective of giving anaethseia to his patients.
In the field of opthalmology too Al razi gave an account of the operation for the extraction of the catract and also the first scientist to discover the effect of the intensity of light on the eye.The modern studies confirm his understanding on the subject thus making him a great physician of all the times.

[B]ABU ALI IBN E SINA:[/B]

Endowed with great powers of absorbing and retaning knowledge this Muslim scholar also made valuable contributions to the field of science.He is considered to be the founders of Medicine and also added his great efforts to the fields of Mathematics,Astronomy,Medicinial Chemistry,Philosophy,Palae ontology and Music.
His most famus book is "Al Qannun" which brings out the features of human physiology and medicine.
Sina is also considered as a father of the science of Geology on account of his invaluable book on mountains in which he discussed matters relating to earth's crust and gave scientific reasons for earthquakes.He is the author of 238 books which are fine instances of his thoughts regarding various subjects in diverse ways.

[B]JABIR BIN HAYAN:[/B]

Introduced experimental research in chemical science which immensly added its rapid development and made him the Father of Chemistry.He devised methods for preparation of important chemicals like hydrochloric acid,nitric acid,and white lead.
Jabir's work also deal with the refinement of metals ,preparation of steel,dyeing of cloth and leather,use of magnese dioxide in glass making,distillation of vinegar to concentrate acetic acid.
Jabir also explained scientifically two principle functions of chemistry,i.e., calcination,and reduction and registerd a marked improvement in teh methods of evaporation,sublimation,distillation and crystillization
He wrote more than 100 books which are one of the most outstanding contributions in the field of science especially the chemical science.

[B]ABDUL HASSAN IBN AL HAITHAM:[/B]

One of the most outstanding Mathematicians, Physiologists,and Opticians of Islam.He contributed to the relams of medicine and philosophy.He wrote more than 200 scientific works on diverse subjects.
Haitham examined the refraction of light rays through transparent objects including air and water.
Infact he was the first scientist to elaborate two laws of refelction of light
He made a number of monumental discoveries in the field of optics ,including one which locates retina as the seat of vision.His book on optics "Kitab Al Manazir" vividly shows his grip on the subject.
He constructed a pinhole camera and studied formation of images .Due to his noteworthy contributions he is regarded as one of the prolific Muslim scientists of all times.

[B]OMAR AL KHAYAM:[/B]

He was an outstanding Mathematician and Astronomer.He was also known as a poet,philosopher and a physician.He travelled to the great centres of learning of the era i.e. Samrakund,Bukhara,and Ispahan.He classified many algebric equations based on their complexity and recognized thirteen different forms of cubic equation.He also classified algebric theories of parallel lines.On the invitation of Sultan Jalal-ud- Din ,he introduced the Jilali calender which has an error of one day in 3770 years.He also developed accurtae methods for determination of gravity
As a poet too,he is known for his Rubaiyat.He made great contributions in the development of mathematics and analytical geomatry which benefitted Europe several years later.

[B]NASIR UD DIN TUSI:[/B]

Al tusi was one of the greatest scientists,Mathematicians,Astronomers,Philosophers ,Theologians and physicians of his time.He was a prolific writer and wrote many treatises on varied subjects like Algebra,Arithmetic,Trignometry,Geometery,Logic,Metaphy sics,medicine,ethics and Theology.
He served as a minister of Halaku Khan and persuaded him to establish an observatory and library after the destruction of baghdad.He worked at the observatory and prepared precise tables regarding the motion of teh planets.These are also known as "Tables of Khan"

[B]ZIA UD DIN IBN BAITAR:[/B]

Was a famous botanist and pharmacopist of middle ages.Because of his intensive travels,he was able to discover many plant species.He wrote many books regarding his field of speciality and is always considered as a prominent scientist among his Muslim counterparts.

[B]3. IMPACT OF SCIENCE ON SOCIETY:[/B]

Science is the organisation of knowledege in such a way that it commands the hidden potential in nature.This hidden potential is surfaced out by the subject of science through the process of understanding.Science has proved to be of enormous beneficial nature .It has made lasting impact on regarding each and every field of human existence.Whether it is concerned with our day to day lives or whether it is related with the various modern developments which have resulted in elevating the living standards of the individuals.
The significant contributions which the study of this subject has made are enumerated below.

[B]SCIENCE AND HUMAN ATTITUDE:[/B]

The various noteworthy scientific advances have helped the individuals in raising up of their self confidence .This subject has enabled the human beings to control and modify their needs and requriements.With greater understanding of teh scientific phenomena human beings have now become more confident about teh encironmental issues as compared to the people in the past.Infact science has promoted and paved teh way for teh independent and logical thinking.

[B]SCIENCE AND HUMAN HEALTH:[/B]

Before the development of modern medicinal factors,a large number of people used to loose their precious lives beacuse of the unavailibilty of the sources and medicines for a proper health care.With the advancements of scinece now the human life expectancy rate has increased as the various modern developments in the field of health care has helped in warding off the dangerous diseases..
The revolutions in surgery and medicine the infectious diseases like small pox, malaria, typhoid etc. have been eradicated.Thus science has improved the health standards of the people.

[B]SCIENCE AND TRAVEL:[/B]

People used to travel on foot before the inventions of automobiles,aeroplanes and steam engines.They also used animal carts and camels for the purpose of moving from one palce to another.However,the modern scientific inventions have proved to be of great signinficance as it has added speed to the area of travel.The quick means of transportation have decreased the distances and is a source of saving time.Infact it would not be wrong to regard that these inventions have added much peace to the lives of the modern men.

[B]SCIENCE AND COMMUNICATION:[/B]

Science has also played a significant part in the development of the modern communication technology.Earlier people were living in isolation because of the slow means of communication.Now the well developed,efficent media have made it possible to communicate with each other more rapidly and quickly.The impact of mass media is enormous.The use of computers and televisions have made the world a global village where an event in one part of the world leaves an influence on the other.

[B]DEMERITS OF SCIENCE:[/B]

Every invention of science has got its own merits and demerits.The most serious invention that science has contributed to is the development of the weapons of mass destruction like the atom and nuclear bombs.The recent wars have greatly showed that how much destruction can be brought about with the use of these lethal weapons.Infact these modern inventions of science have resulted in the elevation of the anxiety and unrest in the modern societites.

Another noteable demerit which the study of this subject has lead to the rise in the environmental deterioation.Day by day the pollution factor is increasing which has proved to be very toxic and harmful for the human health.Not only the human health it is also proving fatal for the animals as well as the existing plants.

The rapid developments of science and industrialization has also divided the world.The developed and the undeveloped.This divison has lead to a widening gap between the status and teh living standards of people.There is economic disparity which has also given rise to class distinction

--[B]4.UNIVERSE:[/B]

The BIG BANG THEORY about the universe is the most widely acceptable theories with regard to the origin of the universe. According to the big bang, the universe was created sometime between 10 billion and 20 billion years ago from a cosmic explosion that hurled matter and in all directions.All the glaxies were formed from this matter .
Observations of these glaxies show that they are still moving apart from each other .The universe is expanding Some scientists have suggested another theory as "steady theory:" to explain the process of the evolution of the universe.However the general notion on which all scientists agree is the theory of Big Bang.

Steady theory is the theory about the universe and the observations by the astronomers have shown that the glaxies are moving away from each other and the universe seems to be expanding.The theory shows that the new matter is always being created to fill the space left by this expansion.The new matter moves apart and forms glaxies which continues to move apart.This means that the universe always look exactly the same.It has no beginnig or end but in a steady state.However many observations have suggested that the universe has not always looked like the same.

[B]THE FUTURE OF UNIVERSE:[/B]
At present the universe is expanding but the astronomers have questioned that whether or not this expansion will continue .Certain observations which have been made in this regard is that one possible ending of the universe will be the "big crunch".The galaxies and other matter may be moving apart but their motion is restrained by their mutual gravitational attraction.If there is a sufficent matter in the universe gravity will eventually win and begin pulling teh galaxies together again causin gthe universe to experience a reverse of the big bang i.e., the BIG CRUNCH.
However there is a possibility that there is not enough matter in the universe for the big crunch to happen.This means that if it happens then the universe will continue to expand forever .

--[B]5.GALAXY:[/B]

Galaxy is a huge number of stars grouped together.The term galaxy can also be described as a collection of dust ,gas and stars measuring thousands of parsecs across.Galzxy contains 10000million stars and looks like a disc with a fat centre and spiral arms.From the front it looks like a convex lens.s

[B]Classes of galaxy:[/B]
Two broad classes of galaxy are there.
1.Ellipitical
2.Spiral
The spiral galaxies are further sub divided into normal which constitutes of majority of spirals and barred spirals.Barred spirals have their centre in the form of the bar .
The ellipitical galaxies range from E 0 to E 7 from an almost spherical shape to a flattened disc.

[B]Milky way:[/B]

Our galaxy is a spiral galaxy about 30,000 parsecs across.There are more than 200 billion stars in the galaxy.Its disc appears as a faint white band that is responsible for dividing the white sky at the night into two.The name of our galaxy is mily way.

The galaxy has three spiral arms called the Orion,Perseus,and sagittarius arms and the whole system is rotating in space.The sun revolves around teh nucleus of teh galaxy once in 225 million years.This duration is also called the cosmic year.

--[B]6.SOLAR SYSTEM:[/B]

The solar system includes nine planets and sun being at the centre.All the planets revlove around teh sun .The solar system also includes the asteroids,meteors and numerous comets.All of these travel around the sun in a particular orbit .The planets which are the significant part of the solar system namely,Mercury,venus,earth,mars,Jupiter,Saturn<ur anus,neptune and the pluto.

All the theories about teh formation of teh solar system agree on two facts.One is that the age of solar system is 4.5billion years and secondly the planets were formed from the gas and dust within the vicinity of the sun.The gas and dust condensed into tiny bodies which eventually built up the present day planetary system.

[B]MOTION OF THE PLANETS[/B]

The planets perform two types of motions.
1,rotation at tehir axisis
2.revolution or the orbital motion along their orbits around the sun.

[B]THE AGE OF THE SOLAR SYSTEM:[/B]

Meteoric evidence suggests that the solar system is 4530+20 million years old.and that was formed in less than 25 million years.
The solar system is believd to be formed from a globe of gas and dust that consisted mainly of hydrogen

--[B]7.THE SUN[/B]

The sun is the most significant star for the existence and life of living beings on earth.The whole life on earth depends on this brightest object in the sky.The living things get their energy from sun and the appropriate distance of earth from sun maintains an appropriate temeprature which is ideal for the survival of all the life present on earth.
The sun is the principle source of energy for all the planets of the solar systems .Through a constant stream of particles that flow outward from the sun ,heat,radiation,light and UV rays are emitted.the UV rays that reach the earth from sun are considered to be the most harmful ones.Most of the UV and other high energy radiation are absorbed by the Ozone layer and the atmosphere of the earth.This stream of particles is called solar wind.

[B]STRUCTURE OF THE SUN:[/B]

The visible surface of the sun is called photosphere which is a turbulent region and is 570 kilometere deep.
The layer outside the photosphere is chromosphere which is a broad layer and is several miles thick.
The outside layer of the sun is corona.Energy released by the sun passes from chromospher to the corona and then to the outer space.

--[B]8.EARTH:[/B]

The third farthest planet from the sun is earth.The earth rotates on its axis in about 24 hours.The diametre of earth is 12756 km.The earth completes its rotation along its axis in 23.9 hour and one tip along its orbit in 365 days,6 hours and 9 minutes and 9.4 seconds.The orbit of the earth is not a circle but a ellipse .

[B]STRUCTURE OF THE EARTH:[/B]

The earth has four major structural components.
1.The Crust
2.The Mantle
3.The Outer core
4.The Inner Core.

[B]THE CRUST:[/B]The upper most layer of the earth is called the crust.A solid and a complex layer of the lithosphere in both physical and chemical nature.The crust is composed of wide variety of rocks which are known as sedementry rocks .The crust is further divided into ocean crust and continental crust.

[B]THE MANTLE:[/B]According to the various kinds of scientific evidneces the upper mantle of teh earth is made up of silicate minerals.The temperature increases rapidly with depth in outer of the earth.Due to high temperatures the rocks start melting .These molten rocks form the basis of lava which erupt from ocanic volcanoes.

[B]THE CORE:[/B]The core starts where marked physical and chemical changes occur across the vore mantle boundries.The outer core is thought to be made of mixture of melted iron and nickle.In the inner core the mixture is thought to be nickle and iron alloy.
[B]
ATMOSPHERE OF THE EARTH:[/B]

The chief gases in the atmosphere of the earth are,
Nitrogen 78.09%
Oxygen 20.95%
Argon 0.93%

The remaining 0.03% is made of carbon dioxide,small quantities of neon,helium,ozone and hydrogen and minute traces of krypton,methane,xenon and other gases.
Another important constituent of the atmosphere is water vapour which makes up 4 percent by volume and 3 percent by weight.
Life is not possible without the atmosphere of the earth Oxygen present in the atmosphere is necessary for both animals and plants for respiration.Carbon dioxide is needed by teh plants which use this gas in the process of photosynthesis.Water vapours present in the earth are necessary for the process of rain and otehr percipitation.
The atmosphere is a valuable natural source of many gases that are widely needed in industry,argon for the purpose of welding and oxygen is required for hospitals and other metal industries.
the earth's atmosphere alo posseses the protective role against the dangerous UV rays and other high radiative energy from space.The atmosphere of the earth absorbs these rdiations which are a cause of various health hazards.

--[B]9.MINERALS[/B]

A mineral is an inorganic substance formed naturally.They are infact building blocks from which rocks are made and they may form crystals.
Minerals are produced by the physical force of the earth.They are the basic units of rocks .Every rock can be considered as the accumulation of minerals.geologists classify rock principally according to the way which they are formed ,not according to their composition as most rocks consists of two or more than two different minerals.

As rocks are formed by minerals,therefore there are three kinds of rocks igneous,sedimentary and metamorphic.

The igneous rocks are formed when the molten magma cools and solidifies .
The sedimentary rocks originate from the deposits of material worn away from the plants and animals and also by the pre existing rocks.
Metamorphic rocks are formed by the alteration of pre existing rocks by great heat or pressure.

The abundent element in these rocks is oxygen and silicon.because of this the mineral silica is very often found in the rocks.In the rocks the silica is combined with other elements such as aluminium,calcium,iron,magnesium,pottasium,or sodium.

--10.[B]SOLAR AND LUNAR ECLIPSES:[/B]

[B]ECLIPSE:[/B]
An eclipse is a New or Full Moon that occurs near the Moon's Nodes. Because the Moon and Sun are so close to the Nodes, they are aligned perfectly enough with the Earth to cast a shadow.

[B]SOLAR ECLIPSE:[/B]

The solar eclipse takes place when the light of the sun is partially or totally cut off from the earth by the moon which comes in between both these celestial bodies.i.e., sun and the earth.

However the solar eclipse occurs only at new moon.As moon is of the similar size to that of the sun,therefore when it passes directly between the earth and the sun it obscures it completely.

There are three types of eclipse.
1.Total
2.Partial
3.annular

The total eclipse is possibel when the apparent sizes of both sun and moon are equl to each other as the moon can completely obscure the bright disc of sun called photosphere.

The Partial eclipse occurs when the sun,moon and earth are not exactly in line.Therefore the moon covers the small part of the sun.

The annular eclipse takes place when the moon's size is too small to completely cover the sun's photosphere which therefore appears as a bright ring around the sun.

[B]
LUNAR ECLIPSE:[/B]

The passing of earth directly between the moon and the sun results in a lunar eclipse.
Like the solar eclipse the lunar eclipse also has three different types.
A total lunar eclipse occurs when when the whole moon passes through the umbra.In case of partial eclipse the entire moon passes through the penumbra and only part of it passes through the umbra. and in a penumbral eclipse the moon passes through only the penumbra.


[B]11.DAY AND NIGHT AND THEIR VARIATION:[/B]

The rotation of the earth is responsible for the day and night varaitions.While rotating the half of the earth faces the sunlight while the other half faces away from the sun.The hemisphere of the earth that faces the sun has day time while the hemisphere that faces away from the sun has night time.
Earth completes its rotation in 24 hours and during this 24 hour duration the variation between day and night occurs.

[B]12. ENERGY 13.SOURCES AND RESOURCES OF ENERGY:[/B]

The ability to do work is energy.The significant sources of energy are coal,gas,wood and oil.These sources area slo called the rpimary sources of energy.Electricity which is reagrded as a scondary source of energy is produced by thses primary sources.For the poduction of electricity the sources of nuclear fiision ,sunlight and water are also employed as the primary sources.

[B]CONVENTIONAL AND NON CONVENTIONAL SOURCES OF ENERGY:[/B]

The sources of energy that are used for the objective of power generation are called conventional sources of energy.whereas the sources that are not utilized for the factor of electricity generation are included in the category of non conventional sources.However these categories change with time like once the nuclear energy was considered under a non conventional source of energy but with the modern discoveries now it is considered to be an important source of energy.

[B]FORMS OF ENERGY:[/B]
COAL: Coal is considered to be an important source of energy .Almost 30 % of worlds power production is dependent on this form.It is a fosil fuel .The organic matter of plants is buried in rocks and soils.The pressure and heat changed this organic material to peat,lignite and then coal.

[B]PETROLEUM:[/B]
Another essential form of enrgy is the use of petroleum.It is also a fosil fuel and a crude oil.Through the process of fractional distillation,the constituients of petroleum are seperated .Major oil producin countries are USA,SAUDI ARABIA,ALGERIA and IRAN ,KUWAIT.

[B]NATURAL GAS:[/B]
Gas is a cheap source of energy and is an organic matter .It is also used for power generation and its major constituent elements are methane,ethane,propane and other hydrocarbons.
the natural gas is abundntly used in Pakistan especailly.

[B]HYDROELECTRIC POWER GENERATION:[/B]
Falling water in the mountanious areas is used as a source of mecahnical energy to rotate turbines and generate electricity.The process of electromagnetic induction is used for this purpose.

[B]SOLAR ENERGY:[/B]
The solar energy is used in photoelectric cells.When light strike certain heavy metals electricity is produced.Saudi Arabia,France and other european countries are utilizing this significant source of energy to heat buildings,power cars and other communication systems.

[B]NUCLEAR ENERGY:[/B]
This form of energy is now being used by the countries like USA<UK<CANADA.In this source of energy is usually released in the form of heat which is first used to heat water and get steam.This steam is used to run a turbine which in eturn generates heat.

--[B]14.ENERGY CONSERVATION:[/B]

By energy conservation it is meant that energy can neither be created nor destroyed but only converted into other forms. This principle infact, is also known as the "law of conservation of energy".

For instance a pendulum that moves to and fro with the bob changing its speed from maximum to teh lowest.In this process the kinetic energy is greatest at the lowest point of teh swing and zero at teh highet.howver the potential energy is maximum at the highest point and is zero at teh lowest.This shows that kinetic energy changes to another form of energy .i.,e potential energy.

Similarly in every production of work all forms of energy generate in this manner.Heat energy is converted to light energy in some cases whereas in some the chemical energy is changed to the potential energy

--[B]15.CERAMICS:[/B]

Ceramics include a vast variety of inorganic ,non mettalic materials which require high temperature heating for preparation.The most famous forms of ceramic are pottery,bricks,tiles and sanitary ware.Infact the ceramics have a wide variety of usage in most sectors especailly in the industrial sector.

[B]RAW MATERIAL:[/B]

The raw material available for ceramic preparation is usually the clay which is is found benetah the top soil .This material is formed through the break down process of rocks affected from the chemical procees and the weather conditions.This raw material is very cheap and can be found in huge quatity.
This raw material when mixed with water can be shaped and moulded in any form according to the requirements or usage.It becomes hard at heating thus making it more durable and strong.

[B]KINDS:[/B]

Three kinds of pottery are in use at the present times.
1.EARTHENWARE
2.STONEWARE
3PORCELAIN

[B]EARTHENWARE:[/B]One of the cheapest and common style of pottery is earthenware.It is easy to prepare and is heated at low temperature.However it is not durable and is dull,porous and absorbent.

[B]STONEWARE:[/B]This kind of pottery is ectremely hard and strong as is emplyed in the making of heavy dishes or jugs ,sanitary wares etc.Howver it can hold liquids and is semi vertious and glass like unlike earthenware.

[B]PORCELAIN:[/B]This is the finest and the most refined form of pottery.It is translucent and strong light can shine through it.Porcealin is also called chinaware as the original technique originated from China.

[B]
--17.SEMI CONDUCTORS:[/B]
Semi-conductors are materials with an electrical conductivity that increases with increasing temperature, a trend that is opposite to that of metals. Semi-conductors characteristically have a band gap between the valence and conduction bands that is smaller than that found in the insulators. The reason the conductivity increases is because as the temperature increases more electrons become thermally excited and are able to jump the band gap between the valence and conduction band. An example of this is silicon.
[B]
n-Type Conductivity[/B]

When a foreign atom with an excess of electrons is added to a pure semi-conductor, the result is a n-type semi-conductor, so named because the charge carriers are negative. This increases the conductivity because a donor band, which is filled with electrons, is introduced near to the conduction band in the band gap. This greatly decreases the band gap which the electrons must jump. Therefore, more electrons are able to get to the conduction band and hence a greater conductivity is the result. An example of an n-type semi-conductor is germanium doped with phosphorous.

[B]p-Type Conductivity[/B]

When foreign atoms with less than 2N electrons are added, the result is a p-type semi-conductor, so called because the charge carrier is a positive hole. The foreign atoms create an acceptor band very close to the valence band that is empty. The result is that the band gap is deceased between a full and empty band. Electrons are then able to easily jumpfromthe valence band into the acceptor bands where they are trapped creating positive holes in the valence band. These positive create a means for the electrons to move within the valence band, thus increasing the conductivity.

--[B]18.RADIO:[/B]

Radio is based on the principle that electrical signals have the capacity of travelling without the wire.Radio signals are carried by electromagnetic waves which travel through space at a speed of light.

The sound waves enter through a microphone in which a coil ,a metal ribbon vibrates to change spund in an electric current.This signal of sound combines with a carrier signal which is at higher radio frequncy.The carrier is modulated by audio frequency signal.This modulated carrier signal get transfers to transmitting aerial where radio waves are emitted in all directions.

The received waves are fed into a radio frequency amplifier to stengthen,They pass to a detector which seperates the audio frequency signal from the carrier wave.The currents that are obtained ae identical to those that left the microphone at the broadcasting station.They are amplified and fed to the loudspeaker.The loudspeaker acts like a microphone,similar to the process that produces sounds like the original sound.
--[B]
19.TELEVISION[/B]

The tv works through the electromagnetic signals that are transmitted,received and converted back to original patterns.The sound transmission is very much similar to radio.In picture transmission the fundamental component is the camera which is responsible for changing the image into electrical impulses..The cathode ray tube at teh other end converts the apttern of electrical impulses into visible images.

Inside the TV camera an illuminated plate emits electrons.The electrons travel to a plate which is called a target plate.The electrical pattern that produces afterwards is transmitted to to the transmitter where the synchronizing pulses are added.Before the final output is fed to the transmitting aerials the sound signal is added.

For transmission VHF and UHF frequencies are used .The receiver is based on the superheterodyne principle,the sound,the vision are received at the seperate intermediate frequency amplifiers,detectors and output stages.the electron beam is made to scan the screen of teh cathode,ray tube and in step with the beam in the tv camers.A picture is then received on the screen.

[B]20.TELEPHONES[/B] :phone

The telephone consists of coils of fine insulated wire that is wound around a permanent horse shoe magnet.A soft iron disc diaphragm is held near the end of the magnet.The magnet lines of force gather in this disc.When the disc is thrown into vibration by a human voice,the number of lines of force passing through the coil changes and a flutuating current is induced.At the receiving end the terminals over the coil wound over the oles of another horse shoe magnet produces the similar vibrations that are produced at the transmitting end and thus helps in producing the sound.

--[B]21.CAMERA[/B] :lier
Equipment for taking photographs which usually consists of a lightproof box with a lens at one end and light-sensitive film at the other.

Photography is undoubtedly one of the most important inventions in history -- it has truly transformed how people conceive of the world. Now we can "see" all sorts of things that are actually many miles -- and years -- away from us. Photography lets us capture moments in time and preserve them for years to come.

The basic technology that makes all of this possible is fairly simple. A still film camera is made of three basic elements: an optical element (the lens), a chemical element (the film) and a mechanical element (the camera body itself). As we'll see, the only trick to photography is calibrating and combining these elements in such a way that they record a crisp, recognizable image.

EVERY camera has these basic parts.
This first and main part is called the body.

The second part is the shutter which might be located in the lens (leaf shutter) or it might be located right in front of the film (focal plane shutter).

The shutter controls WHEN the light enters the camera and for how long it enters. The shutter in the lens is often faster and quieter, but makes changing the lens difficult. The shutter in front of the film allows for easy lens removal, but is often loud and slow. A good camera will have some way of adjusting the time the shutter is open plus there has to be some type of release for the shutter.

The lens lets in light. The larger the lens the more light. The lens also effects how large the image appears based on the focal length of the lens. The aperture is located in the lens and is a set of leaf like piece of metal that can change the size of the hole that lets in light. We consider the lens to be part of the shutter as we do not actually need a lens to focus an image if we have a small enough hole to let in the light.

Finally, the third part is film holder inside the camera. This must have some attachment that allows for the film to be moved which can either be a lever or a motor.

--[B]22.LASER:[/B]

Laser light has several features that are significantly different from white light. To begin with, light from most sources spreads out as it travels, so that much less light hits a given area as the distance from the light source increases. Laser light travels as a parallel beam and spreads very little.

Furthermore, laser light is monochromatic and coherent. White light is a jumble of colored light waves. Each color has a different wavelength. If all the wavelengths but one are filtered out, the remaining light is monochromatic. If these waves are all parallel to one another, they are also coherent: the waves travel in a definite phase relationship with one another. In the case of laser light, the wave crests coincide and the troughs coincide. The waves all reinforce one another. It is the monochromaticity and coherency of laser light that makes it ideal for recording data on optical media such as a CD as well as use as a light source for long haul fiber-optic communications.

The laser uses a process called stimulated emission to amplify light waves. (One method of amplification of an electromagnetic beam is to produce additional waves that travel in step with that beam.) A substance normally gives off light by spontaneous emission. One of the electrons of an atom absorbs energy. While it possesses this energy, the atom is in an excited state. If the electron gives off this excess energy (in the form of electromagnetic radiation such as light) with no outside impetus, spontaneous emission has occurred.

If a wave emitted by one excited atom strikes another, it stimulates the second atom to emit energy in the form of a second wave that travels parallel to and in step with the first wave. This stimulated emission results in amplification of the first wave. If the two waves strike other excited atoms, a large coherent beam builds up. But if they strike unexcited atoms, they are simply absorbed, and the amplification is then lost. In the case of normal matter on Earth, the great majority of atoms are not excited. As more than the usual number of atoms become excited, the probability increases that stimulated emission rather than absorption will take place.

Physicist Gordon Gould invented the laser in 1958. The first working model was built in 1960 by T.H. Maiman. It contained a synthetic, cylindrical ruby with a completely reflecting silver layer on one end and a partially reflecting silver layer on the other. Ruby is composed of aluminum oxide with chromium impurities. The chromium atoms absorb blue light and become excited; they then drop first to a metastable level and finally to the ground (unexcited) state, giving off red light. Light from a flash lamp enters the ruby and excites most of the chromium atoms, many of which fall quickly to the metastable level. Some atoms then emit red light and return to the ground state. The light waves strike other excited chromium atoms, stimulating them to emit more red light. The beam bounces back and forth between the silvered ends until it gains enough energy to burst through the partially silvered end as laser light. When most of the chromium atoms are back in the ground state, they absorb light, and the lasing action stops. In continuous-wave lasers, such as the helium-neon laser, electrons emit light by jumping to a lower excited state, forming a new atomic population that does not absorb laser light, rather than to the ground state.

--[B]23.MICROSCOPE [/B]

Microscopes give us a large image of a tiny object. The microscopes we use in school and at home trace their history back almost 400 years.

The first useful microscope was developed in the Netherlands between 1590 and 1608. There is almost as much confusion about the inventor as about the dates. Three different eyeglass makers have been given credit for the invention. The possible inventors are Hans Lippershey (who also developed the first real telescope), Hans Janssen, and his son, Zacharias.
Lens quality in early microscopes was often poor so the images were not very clear. But even these rather crude microscopes were a great help in learning more about animals and plants.

The microscope works a lot like a refracting telescope except that the object is very close to the objective lens.The clips on the microscope's flat stage hold the slide in place.A mirror at the bottom of the microscope reflects light rays up to the daphnia through a hole in the stage. Objective lenses magnify the image which is made even larger when we see it through the eyepiece lenses.

The objective lens is usually a compound lens, a combination of two lenses made from different kinds of glass. When only one lens is used, we often get distortion. This distortion (chromatic aberration) is caused because the colours making up light are not refracted (bent) the same amount when passing through a glass lens. When we use a compound lens, any distortion from the first lens is corrected by the second lens.

Different types of microscopes have been used to look at human cells, identify minerals, solve crimes.
Microscopes are an essential tool in medicine too. They have been used to identify the causes of many deadly diseases like malaria and tuberculosis. Microscopes can also help to find out why a person or animal died.

Scientists can even use a microscope to figure out where illegal drugs come from. For example, looking at opium crystals through a microscope reveals different shapes depending on where the poppies they came from were grown. This information can help pinpoint the source of illegal drugs.

--[B]24.COMPUTERS:[/B]

Computer is an electronic device that can accept data,aaply a series of logical processess to it and supply the results of tehse processes as information.Computers are also used to perform a complex series of mathematical calculations at very great speed which makes them great for the numerous purposes.

[B]KINDS:[/B]

The two main kinds of computers are

1.Analog computer
2.Digital computer.

in analog computer the numbers are represented by magnitudes of physical quantities as voltage,magnitudes etc.

The digital comouter is in which numbers are expressed directly as digits usually in the binary notion.The digital computers are howver more useful and versatile.

[B]COMPUTER BASICS:[/B]

Computer is mainly based on
1.Hardware
2.Software
3.Input

Hardware consists of devices, like the computer itself, the monitor, keyboard, printer, mouse and speakers. Inside your computer there are more bits of hardware, including the motherboard, where you would find the main processing chips that make up the central processing unit (CPU). The hardware processes the commands it receives from the software, and performs tasks or calculations.

Software is the name given to the programs that you install on the computer to perform certain types of activities

Input is when we type a command or click on an icon, we tell the computer what to do. That is called input.

[B]WORKING:[/B]

A computer is based on various components which when combined together perform useful functions.There is a CPU,the central processing unt which performs all the computations.It is supported by by memory which holds the current programme and data and logic arrays which helps in the provision and moment of information around the system.
The program and data ,text,figures and images or sounds are into in the computer which then processes the data and the outputs the results.
[B]
TYPES:[/B]

There are four main types of computers.
1.MICRO COMPUTERS
2.MINI COMPUTERS
3.MAIN FRAMES
4.SUPER COMPUTERS

Micro computers are the smallest and the most common an are used in small bussinesses,homes,schools.They are also reffered as home computers.
The mini computers are also known as personal computers and ar genrally larger and used in medium sized bussinesses and university departments.
The mainframes are found in alrge organizations companies and government departments in advanced countries mostly.

The super computers are the most powerful of all as they are especially used for highly complex scientific tasks as analyzing results of nuclear physics experiments and weather forecasting.


--[B]25 SATELLITES:[/B]

Satellite technology has emerged tremendously over the last 50 years since Arthur C. Clarke first invented it. Today, satellite technology is all around us and has become a very useful, everyday application of modern telecommunications. Satellite systems can provide a variety of services including broadband communication systems, satellite-based video, audio, internet and data distribution networks, as well as worldwide customer service and support.

[B]What is a satellite ?[/B]

An artificial satellite is a man made object placed into orbit around the Earth for the purpose of scientific research, weather reports, or military reconnaissance. Scientific satellites are set into orbit to observe the space environment, the Earth, the Sun, stars and extra galactic objects. These satellites have retrieved a huge amount of information helpful to scientific research. Weather satellites are used every day for meteorological forecasts and in shipping. Also military satellites play a important role in today's modern military. Satellites are extremely important today. All artificial satellites have certain features in common. They all include radar systems, sensors like optical devices in observation satellites and receivers and transmitters in communication satellites. Solar cells are used to generate power for the satellites and in some cases ,nuclear power is used. All satellites need altitude-control equipment to keep the satellite in the desired orbit.

[B]Orbit of a Satellite[/B]

The orbit of the satellite is achieved when it is given a horizontal velocity of 17,500 mph at sea level causing the Earth's surface to curve away and as fast as it curves away gravity pulls the object downward and at this point the satellite achieved orbit. As the altitude of the satellite increases, its velocity decreases and its period increases. The period of satellite is the time the satellite takes to make on revolution around the Earth. Satellites in later orbit are called synchronous satellites. If the satellite orbits in a equatorial plane, it is called geostationary which means it is always over the same place on earth at all times. This form of orbit is used in weather for reports of a certain area at all times. The orbit of a satellite is very scientific but not hard to understand.

[B]26.ANTIBIOTICS:[/B]

A chemical substance derivable from a mold or bacterium that kills microorganisms and cures infections.

Antibiotics are drugs used to kill or harm specific bacteria. Since their discovery in the 1930s, antibiotics have made it possible to cure diseases caused by bacteria such as pneumonia, tuberculosis, and meningitis - saving the lives of millions of people around the world.

But antibiotics must be used wisely. Because bacteria are living organisms, they are always changing in an effort to resist the drugs that can kill them. When antibiotics are used incorrectly, bacteria can adapt and become resistant. Antibiotics are then no longer useful in fighting them. Antibiotic resistance is now a major public health issue. The correct use of these drugs is the best way to ensure that antibiotics remain useful in treating infections.

[B]27.VACCINES:[/B]

Immunogen consisting of a suspension of weakened or dead pathogenic cells injected in order to stimulate the production of antibodies can be defined as vaccines.

[B]How Vaccines Work[/B]

Disease causing organisms have at least two distinct effects on the body The first effect is exhibiting symptoms such as fever, nausea, vomiting, diarrhea, rash, and many others.the second effect generally leads to eventual recovery from the infection: the disease causing organism induces an immune response in the infected host. As the response increases in strength over time, the infectious agents are slowly reduced in number until symptoms disappear and recovery is complete.

The disease causing organisms contain proteins called "antigens" which stimulate the immune response. The resulting immune response is multi-fold and includes the synthesis of proteins called "antibodies." These proteins bind to the disease causing organisms and lead to their eventual destruction. In addition, "memory cells" are produced in an immune response. These are cells which remain in the blood stream, sometimes for the life span of the host, ready to mount a quick protective immune response against subsequent infections with the particular disease causing agent which induced their production. If such an infection were to occur, the memory cells would respond so quickly that the resulting immune response could inactivate the disease causing agents, and symptoms would be prevented. This response is often so rapid that infection doesn't develop - and we get immune from infection.

Vaccines are effective in preventing disease not only in individuals, but also in communities. This type of protection is called "herd immunity." When a disease spreads from one human to another, it requires both an infected individual to spread it and a susceptible individual to catch it. Herd immunity works by decreasing the numbers of susceptible people. When the number of susceptible people drops low enough, the disease will disappear from the community because there are not enough people to carry on the catch-and-infect cycle. The greater the proportion of vaccinated members of the community, the more rapidly the disease will disappear.


[B]28.FERTILIZERS:[/B]

Any substance such as manure or a mixture of nitrates used to make soil more fertile are fertilizers.

Fertilizers are plant nutrients. Nutrients exist naturally in the earth's soil and atmosphere, and in animal manure. However, naturally occurring nutrients are not always available in the forms that plants can use. Therefore, man-made fertilizer is vital to food production. Man-made and natural fertilizers contain the same ingredients, but man-made fertilizers act more quickly and are less susceptible to weather changes. Farmers, ranchers and gardeners add these fertilizers directly to the soil, where they can be absorbed by plants for healthy growth. Incorporated into a program of best management practices, which includes soil testing, man-made fertilizer use leads to higher
crop yields and greater environmental protection.


--[B]29.PESTICIDES:[/B]

[B]Types of Pesticides[/B]

A pesticide is any chemical which is used by man to control pests. The pests may be insects, plant diseases, fungi, weeds, nematodes, snails, slugs, etc. Therefore, insecticides, fungicides, herbicides, etc., are all types of pesticides. Some pesticides must only contact (touch) the pest to be deadly. Others must be swallowed to be effective. The way that each pesticide attacks a pest suggests the best way to apply it; to reach and expose all the pests. For example, a pesticide may be more effective and less costly as a bait, rather than as a surface spray.

[B]Insecticides[/B]

Insecticides are chemicals used to control insects. Often the word "insecticide" is confused with the word "pesticide." It is, however, just one of many types of pesticides. An insecticide may kill the insect by touching it or it may have to be swallowed to be effective. Some insecticides kill both by touch and by swallowing. Insecticides called Systemics may be absorbed, injected, or fed into the plant or animal to be protected. When the insect feeds on this plant or animal, it ingests the systemic chemical and is killed.

[B]Miticides and Acaricides[/B]

Miticides (or Acaricides) are chemicals used to control mites (tiny Insecticides spider-like animals) and ticks. The chemicals usually must contact the mites or ticks to be effective. These animals are so numerous and small, that great care must be used to completely cover the area on which the mites live. Miticides are very similar in action to insecticides and often the same pesticide kills both insects and mites. The terms "broad spectrum," "short term," and "residual" are also used


[B]Fungicides[/B]

Fungicides are chemicals used to control the fungi which cause molds, rots, and plant diseases. All fungicides work by coming in contact with the fungus, because fungi do not "swallow" in the normal sense. Therefore, most fungicides are applied over a large surface area to try to directly hit every fungus. Some fungicides may be systemic in that the plant to be protected may be fed or injected with the chemical. The chemical then moves throughout the plant, killing the fungi. to describe miticides.

[B]Herbicides[/B]

Herbicides are chemicals used to control unwanted plants. These chemicals are a bit different from other pesticides because they are used to kill or slow the growth of some plants, rather than to protect them. Some herbicides kill every plant they contact, while others kill only certain plants.

[B]Rodenticides[/B]

Rodenticides are chemicals used to control rats, mice, bats and other rodents. Chemicals which control other mammals, birds, and fish are also grouped in this category by regulatory agencies. Most rodenticides are stomach poisons and are often applied as baits. Even rodenticides which act by contacting the pest are usually not applied over large surfaces because of the hazard to domestic animals or desirable wildlife. They are usually applied in limited areas such as runways, known feeding places, or as baits.

[B]Nematicides [/B]

Nematicides are chemicals used to control nematodes. Nematodes are tiny hir-like worms, many of which live in the soil and feed on plant roots. Very few of these worms live above ground. Usually, soil fumigants are used to control nematodes in the soil.

--[B]30.MICROWAVE OVENS:[/B] :snor

The microwave oven is one of the great inventions of the 20th century .microwave ovens cook food in an amazingly short amount of time.A microwave oven uses microwaves to heat food. Microwaves are radio waves. In the case of microwave ovens, the commonly used radio wave frequency is roughly 2,500 megahertz (2.5 gigahertz). Radio waves in this frequency range have an interesting property: they are absorbed by water, fats and sugars. When they are absorbed they are converted directly into atomic motion -- heat. Microwaves in this frequency range have another interesting property: they are not absorbed by most plastics, glass or ceramics. Metal reflects microwaves, which is why metal pans do not work well in a microwave oven.

[B]HAZARDS:[/B]

No doubt that microwave ovens have added many advatages to the daily lives but their frequent used has been negated by the doctors and physicians because of various serious health hazrads.Among the most serious of them is the cause of cancer.Infact some people have termed the microwaves as the "recipie of cancer."

Micro wave cooking is not natural and therefore it cannont be regarded as healthy.The wave radiations that are generated by a microwave oven during the process of cooking or heating any food item are considered extremely harmful and is conceived as one of teh biggest resources of spreading the stomach and intestinials cancers.

The microwave exposure also reduces the nutritive value of the foods .loss of memory,emotional insatbility and a decrease of intelligence.

Did You Know?
 

Eyes :::::::: Are the most complex organs you possess except for your brain.
Are composed of more than two million working parts.
Can process 36,000 bits of information every hour.
Under the right conditions, can discern the light of a candle at a distance of 14 miles.
Contribute towards 85% of your total knowledge.
Utilize 65% of all the pathways to the brain.
Can instantaneously set in motion hundreds of muscles and organs in your body.
In a normal life-span, will bring you almost 24 million images of the world around you.
The external muscles that move the eyes are the strongest muscles in the human body for the job that they have to do. They are 100 times more powerful than they need to be.
The adult eyeball measures about 1 inch (2.5 cm) in diameter. Of its total surface area only one-sixth is exposed -- the front portion.
The eye is the only part of the human body that can function at 100% ability at any moment, day or night, without rest. Your eyelids need rest, the external muscles of your eyes need rest, the lubrication of your eyes requires replenishment, but your eyes themselves "never" need rest. But please rest them!