Q.2. (a) Fission & Fusion
Nuclear Fission: A nuclear reaction in which an atomic nucleus, especially a heavy nucleus such as an isotope of uranium, splits into fragments, usually two fragments of comparable mass, releasing from 100 million to several hundred million electron volts of energy.
235U + 1 neutron 2 neutrons + 92Kr + 142Ba + ENERGY
Nuclear Fusion: Nuclear fusion is the process by which two light atomic nuclei combine to form one heavier atomic nucleus. As an example, a proton (the nucleus of a hydrogen atom) and a neutron will, under the proper circumstances, combine to form a deuteron (the nucleus of an atom of "heavy" hydrogen).


Q.2. (b)Star & Planet
Star: A self-luminous body that during its life generates (or will generate) energy and support by thermonuclear fusion.
Explanation: Any massive celestial body of gas that shines by radiant energy generated inside it. The Milky Way Galaxy contains hundreds of billions of stars; only a very small fraction are visible to the unaided eye. The closest star to Earth is the Sun. The closest star to the Sun is about 4.2 light-years away; the most distant are in galaxies billions of light-years away. Single stars such as the Sun are the minority; most stars occur in pairs and multiple systems (see binary star). Stars also associate by their mutual gravity in larger assemblages called clusters (see globular cluster; open cluster). Constellations consist not of such groupings but of stars in the same direction as seen from Earth. Stars vary greatly in brightness (magnitude), colour, temperature, mass, size, chemical composition, and age. In nearly all, hydrogen is the most abundant element. Stars are classified by their spectra (see spectrum), from blue-white to red, as O, B, A, F, G, K, or M; the Sun is a spectral type G star. Generalizations on the nature and evolution of stars can be made from correlations between certain properties and from statistical results (see Hertzsprung-Russell diagram). A star forms when a portion of a dense interstellar cloud of hydrogen and dust grains collapses from its own gravity. As the cloud condenses, its density and internal temperature increase until it is hot enough to trigger nuclear fusion in its core (if not, it becomes a brown dwarf). After hydrogen is exhausted in the core from nuclear burning, the core shrinks and heats up while the star's outer layers expand significantly and cool, and the star becomes a red giant.
Planet: A relatively small, solid celestial body moving in orbit around a star, in particular the Sun.
Explanation: According to the IAU's current definitions, there are eight planets in the Solar System. In increasing distance from the Sun, they are:
1. Mercury
2. Venus
3. Earth
4. Mars
5. Jupiter
6. Saturn
7. Uranus
8. Neptune
Jupiter is the largest, at 318 Earth masses, while Mercury is smallest, at 0.055 Earth masses.
The planets of the Solar System can be divided into categories based on their composition:
• Terrestrials: Planets that are similar to Earth, with bodies largely composed of rock: Mercury, Venus, Earth and Mars.
• Gas giants: Planets with a composition largely made up of gaseous material and are significantly more massive than terrestrials: Jupiter, Saturn, Uranus, Neptune. Ice giants, comprising Uranus and Neptune, are a sub-class of gas giants, distinguished from gas giants by their significantly lower mass, and by depletion in hydrogen and helium in their atmospheres together with a significantly higher proportion of rock and ice.

Q.2. (c) Pollination & Fertilization
Transfer of pollen from the male reproductive organ (stamen) to the female reproductive organ (pistil) of the same or of another flower or cone. Pollination is not to be confused with fertilization, which it may precede by some time—a full season in many conifers. The most common agents of pollination are flying insects (as in most flowering plants) and the wind (as in many trees and all grasses and conifers), but crawling and hopping insects, snails, bats, primates, rodents, and hummingbirds may also serve.
The union of male and female gametes to form a zygote is known as fertilization.


Q.2. (d) Telescope & Microscope

A telescope is a device that collects light from and magnifies images of distant objects, undoubtedly the most important investigative tool in astronomy. A telescope is an instrument designed for the observation of remote objects and the collection of electromagnetic radiation.


A refracting telescope forms an image by focusing light from a distant objects.
Types of Telescopes:
(1) Optical Telescope: An optical telescope gathers and focuses light mainly from the visible part of the electromagnetic spectrum.
(2) Radio Telescope: Radio telescopes are directional radio antennas that often have a parabolic shape. Radio telescopes are also used to collect microwave radiation.
(3) X-ray and gamma-ray telescopes: X-ray and gamma-ray radiation go through most metals and glasses. Gamma-ray telescopes refrain from focusing completely and use coded aperture masks: the patterns of the shadow the mask creates can be reconstructed to form an image. These types of telescopes are usually on Earth-orbiting satellites or high-flying balloons since the Earth's atmosphere is opaque to this part of the electromagnetic spectrum.

Microscope: An instrument used to obtain an enlarged image of a small object. The image may be seen, photographed, or sensed by photocells or other receivers, depending upon the nature of the image and the use to be made of the information of the image.
(1) Simple Microscope: A simple microscope, hand lens, or magnifier usually is a round piece of transparent material, ground thinner at the edge than at the center, which can form an enlarged image of a small object. Commonly, simple microscopes are double convex or planoconvex lenses, or systems of lenses acting together to form the image.
(2) Compound Microscope: The compound microscope utilizes two lenses or lens systems. One lens system forms an enlarged image of the object and the second magnifies the image formed by the first. The total magnification is then the product of the magnifications of both lens systems (see illustration).

Compound microscope diagram. (After F. A. Jenkins and H. E. White, Fundamentals of Optics, 4th ed., McGraw-Hill, 1976)
The typical compound microscope consists of a stand, a stage to hold the specimen, a movable body-tube containing the two lens systems, and mechanical controls for easy movement of the body and the specimen. The lens system nearest the specimen is called the objective; the one nearest the eye is called the eyepiece or ocular. A mirror is placed under the stage to reflect light into the instrument when the illumination is not built into the stand. For objectives of higher numerical aperture than 0.4, a condenser is provided under the stage to increase the illumination of the specimen. Various optical and mechanical attachments may be added to facilitate the analysis of the information in the doubly enlarged image.




Q.2. (e) Antibiotics & Vaccines
Antibiotics: Substances produced by living organisms which inhibit the growth of other organisms. The first antibiotic to be discovered was penicillin, which is produced by the mould Penicillium notatum and inhibits the growth of sensitive bacteria. Many antibiotics are used to treat bacterial infections in human beings and animals; different compounds affect different bacteria.
Explanation: Antibiotics represent a class of drugs used in the treatment of infections and infectious diseases caused by bacteria. These bacteria possess unique features (e.g., a cell wall, proteins, enzymes) that differentiate them from animal cells. Antibiotics interfere with the production of these bacterial characteristics, resulting in selective killing or growth inhibition of susceptible microorganisms. For example, prior to 1990, infections caused by Streptococcus pneumoniae (e.g., pneumonia, bronchitis, ear infections), were usually treated with penicillin or amoxicillin. Streptococcus pneumoniae possess a cell wall that acts as a protective barrier— a unique feature not found on animal or human cells. Penicillin or amoxicillin, two common antibiotics, bind to that cell wall as it is produced, causing it to weaken and "leak," eventually killing the bacteria without harming the animal host cells.
Vaccines: A vaccine is a medical preparation given to a person to provide immunity from a disease.
Explanation: Vaccines use a variety of different substances ranging from dead microorganisms to genetically engineered antigens to defend the body against potentially harmful antigens. Effective vaccines change the immune system by promoting the development of antibodies that can quickly and effectively attack disease causing microorganisms or viruses when they enter the body, preventing disease development.
In 1961, an oral polio vaccine developed by Albert B. Sabin (1906–1993) was licensed in the United States.






Q.3. (a) Solar System

Definition: The Sun, its eight major planets, the dwarf planets and small bodies, and interplanetary dust and gas under the Sun's gravitational control. Or, the Sun and the bodies moving in orbit around it.
Another component of the solar system is the solar wind. The Sun contains more than 99% of the mass of the solar system; most of the rest is distributed among the planets, with Jupiter containing about 70%.
Explanation: The most massive body in the solar system is the Sun, a typical single star that is itself in orbit about the center of the Milky Way Galaxy. Nearly all of the other bodies in the solar system—the terrestrial planets, outer planets, asteroids, and comets—revolve on orbits about the Sun. Various types of satellites revolve around the planets; in addition, the giant planets all have orbiting rings. The orbits for the planets appear to be fairly stable over long time periods and hence have undergone little change since the formation of the solar system. It is thought that some 4.56 × 109 years ago a rotating cloud of gas and dust collapsed to form a flattened disk (the solar nebula) in which the Sun and other bodies formed. The bulk of the gas in the solar nebula moved inward to form the Sun, while the remaining gas and dust are thought to have formed all the other solar system bodies by accumulation proceeding through collisions of intermediate-sized bodies called planetesimals. Planetary systems are believed to exist around many other stars in the Milky Way Galaxy. Solid evidence for the existence of Jupiter-mass planets around nearby solarlike stars now exists.

Q.3. (b) Causes of Earthquakes
The short answer is that earthquakes are caused by faulting, a sudden lateral or vertical movement of rock along a rupture (break) surface.
However, the two main causes of eartquakes are as follows:
1- Explosive volcanic eruptions: they are in fact very common in areas of volcanic activity where they either proceed or accompany eruptions.
2- Tectonic activity: This activity is associated with plate margins and faults. The majority of earthquakes world wide are of this type.
Explanation: The earth is divided into three main layers - a hard outer crust, a soft middle layer and a center core. The outer crust is broken into massive, irregular pieces called "plates." These plates move very slowly, driven by energy forces deep within the earth. Earthquakes occur when these moving plates grind and scrape against each other.
Geologists and Geographers call the origin of the earthquake the focus. Since this is often deep below the surface and difficult to map, the location of the earthquake is often referred to as the point on the Earth surface directly above the focus. This point is called the epicentre.
Earthquake shockwaves and Types:
Earthquakes are three dimensional events, the waves move outwards from the focus, but can travel in both the horizontal and vertical plains. This produces three different types of waves which have their own distinct characteristics and can only move through certain layers within the Earth. Lets take a look at these three forms of shock waves.
Types of shockwaves:
1- P-Waves
Primary Waves (P-Waves) are identical in character to sound waves. They are high frequency, short-wavelength, longitudinal waves which can pass through both solids and liquids. The ground is forced to move forwards and backwards as it is compressed and decompressed. This produces relatively small displacements of the ground.
P Waves can be reflected and refracted, and under certain circumstances can change into S-Waves.

Particles are compressed and expanded in the wave's direction.
2- S-Waves
Secondary Waves (S-Waves) travel more slowly than P-Waves and arrive at any given point after the P-Waves. Like P-Waves they are high frequency, short-wavelength waves, but instead of being longitudinal they are transverse. They move in all directions away from their source, at speeds which depend upon the density of the rocks through which they are moving. They cannot move through liquids. On the surface of the Earth, S-Waves are responsible for the sideways displacement of walls and fences, leaving them 'S' shaped.

S-waves move particles at 90° to the wave's direction.
3- L-Waves
Surface Waves (L-Waves) are low frequency transverse vibrations with a long wavelength. They are created close to the epicentre and can only travel through the outer part of the crust. They are responsible for the majority of the building damage caused by earthquakes. This is because L Waves have a motion similar to that of waves in the sea. The ground is made to move in a circular motion, causing it to rise and fall as visible waves move across the ground. Together with secondary effects such as landslides, fires and tsunami these waves account for the loss of approximately 10,000 lives and over $100 million per year.

L-waves move particles in a circular path.
Types of Earthquakes:
1- Tectonic Earthquakes:
Tectonic earthquakes are triggered when the crust becomes subjected to strain, and eventually moves. The theory of plate tectonics explains how the crust of the Earth is made of several plates, large areas of crust which float on the Mantle. Since these plates are free to slowly move, they can either drift towards each other, away from each other or slide past each other. Many of the earthquakes which we feel are located in the areas where plates collide or try to slide past each other.
The process which explains these earthquakes, known as Elastic Rebound Theory can be demonstrated with a green twig or branch. Holding both ends, the twig can be slowly bent. As it is bent, energy is built up within it. A point will be reached where the twig suddenly snaps. At this moment the energy within the twig has exceeded the Elastic Limit of the twig. As it snaps the energy is released, causing the twig to vibrate and to produce sound waves.
Perhaps the most famous example of plates sliding past each other is the San Andreas Fault in California. Here, two plates, the Pacific Plate and the North American Plate, are both moving in a roughly northwesterly direction, but one is moving faster than the other. The San Francisco area is subjected to hundreds of small earthquakes every year as the two plates grind against each other. Occasionally, as in 1989, a much larger movement occurs, triggering a far more violent 'quake'.
Major earthquakes are sometimes preceded by a period of changed activity. This might take the form of more frequent minor shocks as the rocks begin to move,called foreshocks , or a period of less frequent shocks as the two rock masses temporarily 'stick' and become locked together. Detailed surveys in San Francisco have shown that railway lines, fences and other longitudinal features very slowly become deformed as the pressure builds up in the rocks, they become noticeably offset when a movement occurs along the fault. Following the main shock, there may be further movements, called aftershocks, which occur as the rock masses 'settle down' in their new positions. Such aftershocks cause problems for rescue services, bringing down buildings already weakened by the main earthquake.
2- Volcanic Earthquakes:
Volcanic earthquakes are far less common than Tectonic ones. They are triggered by the explosive eruption of a volcano. Given that not all volcanoes are prone to violent eruption, and that most are 'quiet' for the majority of the time, it is not surprising to find that they are comparatively rare.
When a volcano explodes, it is likely that the associated earthquake effects will be confined to an area 10 to 20 miles around its base, where as a tectonic earthquake may be felt around the globe.
The volcanoes which are most likely to explode violently are those which produce acidic lava. Acidic lava cools and sets very quickly upon contact with the air. This tends to chock the volcanic vent and block the further escape of pressure. For example, in the case of Mt Pelee, the lava solidified before it could flow down the sides of the volcano. Instead it formed a spine of solid rock within the volcano vent. The only way in which such a blockage can be removed is by the build up of pressure to the point at which the blockage is literally exploded out of the way. In reality, the weakest part of the volcano will be the part which gives way, sometimes leading to a sideways explosion as in the Mt St. Helens eruption.
When extraordinary levels of pressure develop, the resultant explosion can be devastating, producing an earthquake of considerable magnitude. When Krakatoa ( Indonesia, between Java and Sumatra ) exploded in 1883, the explosion was heard over 5000 km away in Australia. The shockwaves produced a series of tsunami ( large sea waves ), one of which was over 36m high; that's the same as four, two story houses stacked on top of each other. These swept over the coastal areas of Java and Sumatra killing over 36,000 people.
By contrast, volcanoes producing free flowing basic lava rarely cause earthquakes. The lava flows freely out of the vent and down the sides of the volcano, releasing pressure evenly and constantly. Since pressure doesn't build up, violent explosions do not occur.











Q.4. (a) Supernova
Definition: A large star in its death throes that suddenly explodes, increasing many thousands of times in brightness.
Explanation: Like novas, supernovas undergo a tremendous, rapid brightening lasting a few weeks, followed by a slow dimming, and show blue-shifted emission lines on spectroscopy, which implies that hot gases are blown outward. Unlike a nova, a supernova explosion is a catastrophic event for a star, leading to its collapse into a neutron star or black hole. Amounts of its matter equal to the mass of several Suns may be blasted into space with such energy that the exploding star outshines its entire home galaxy. Only seven supernovas are known to have been recorded before the 17th century, the most famous in AD 1054; its remnants are visible today as the Crab Nebula. The closest and most studied supernova in modern times is SN 1987A, which appeared in 1987 in the Large Magellanic Cloud. Supernova explosions release not only tremendous amounts of radio energy and X-rays but also cosmic rays; in addition, they create and fling into interstellar space many of the heavier elements found in the universe, including those forming Earth's solar system.
(b) Radioactivity
Definitions:
The spontaneous breaking apart, or decay, of unstable nuclei in isotopes. The unstable radioactive isotope is called the parent, and the products of the decay of the parent are called the daughter isotopes.
Or,
Radioactivity is a property exhibited by certain types of matter that emit radiation spontaneously.
Explanations:
The phenomenon was first reported in 1896 by Henri Becquerel for a uranium salt, and it was soon found that all uranium compounds are radioactive due to the uranium's radioactivity. In 1898 Marie Curie and her husband discovered two other naturally occurring, strongly radioactive elements, radium and polonium. The radiation is emitted by unstable atomic nuclei as they attempt to become more stable. The main processes of radioactivity are alpha decay, beta decay, and gamma decay. In 1934 it was discovered that radioactivity could be induced in ordinary matter by artificial transmutation.


(c) Laser
Definition: A laser is a device that emits light (electromagnetic radiation) through a process called stimulated emission.
Explanation: The term "laser" is an acronym for Light Amplification by Stimulated Emission of Radiation. Laser light is usually spatially coherent, which means that the light either is emitted in a narrow, low-divergence beam, or can be converted into one with the help of optical components such as lenses. The coherence of typical laser emission is distinctive. Most other light sources emit incoherent light, which has a phase that varies randomly with time and position.
Characteristics of Lasers:
The physical size of a laser depends on the materials used for light emission, on its power output, and on whether the light is emitted in pulses or as a steady beam. Lasers have been developed that are not much larger than a common flashlight. Various materials have been used as the active media in lasers. The first laser, built in 1960, used a ruby rod with polished ends; the chromium atoms embedded in the ruby's aluminum oxide crystal lattice were pumped to an excited state by a flash tube that, wrapped around the rod, saturated the rod with light of a frequency higher than that of the laser frequency (this method is called optical pumping). This first ruby laser produced intense pulses of red light. In many other optically pumped lasers, the basic element is a transparent, non-conducting crystal such as yttrium aluminum garnet (YAG). Another type of crystal laser uses a semiconductor diode as the element; pumping is done by passing a current through the crystal.
In some lasers, a gas or liquid is used as the emitting medium. In one kind of gas laser the inverted population is achieved through collisional pumping, the gas molecules gaining energy from collisions with other molecules or with electrons released through current discharge. Some gas lasers make use of molecular dissociation to create the inverted population. In a free-electron laser a beam of electrons is “wiggled” by a magnetic field; the oscillatory behavior of the electrons induces them to emit laser radiation. Another device under development is the X-ray laser, which presents special difficulties; most materials, for instance, are poor reflectors of X rays.
Applications of Lasers:
Lasers have been used in industry for cutting and boring metals and other materials, and for inspecting optical equipment. In medicine, they have been used in surgical operations. Lasers have been used in several kinds of scientific research. The field of holography is based on the fact that actual wave-front patterns, captured in a photographic image of an object illuminated with laser light, can be reconstructed to produce a three-dimensional image of the object. One important result of laser research is the development of lasers that can be tuned to emit light over a range of frequencies, instead of producing light of only a single frequency. Work is being done to develop lasers for communication; in a manner similar to radio transmission, the transmitted light beam is modulated with a signal and is received and demodulated some distance away. Lasers have also been used in plasma physics and chemistry.
Uses
When lasers were invented in 1960, they were called "a solution looking for a problem".[23] Since then, they have become ubiquitous, finding utility in thousands of highly varied applications in every section of modern society, including consumer electronics, information technology, science, medicine, industry, law enforcement, entertainment, and the military.
The first application of lasers visible in the daily lives of the general population was the supermarket barcode scanner, introduced in 1974. The laserdisc player, introduced in 1978, was the first successful consumer product to include a laser, but the compact disc player was the first laser-equipped device to become truly common in consumers' homes, beginning in 1982, followed shortly by laser printers.
Some of the other applications include:
• Medicine: Bloodless surgery, laser healing, surgical treatment, kidney stone treatment, eye treatment, dentistry
• Industry: Cutting, welding, material heat treatment, marking parts
• Defense: Marking targets, guiding munitions, missile defence, electro-optical countermeasures (EOCM), alternative to radar
• Research: Spectroscopy, laser ablation, Laser annealing, laser scattering, laser interferometry, LIDAR, Laser capture microdissection
• Product development/commercial: laser printers, CDs, barcode scanners, thermometers, laser pointers, holograms, bubblegrams.
• Laser lighting displays: Laser light shows
• Laser skin procedures such as acne treatment, cellulite reduction, and hair removal.
Q.4. (d) Semiconductors
Definition: A semiconductor is a solid material that has electrical conductivity in between a conductor and an insulator; it can vary over that wide range either permanently or dynamically.
Working: When electricity or light is applied to semiconductors, they change their state between conductive and non-conductive or reflective and non-reflective. The most significant semiconductor is the transistor, which in digital circuits works like an on/off switch. For analog applications, it may be an on/off switch as well, but is more likely used as an amplifier, taking in a low-voltage signal and outputting a higher voltage.
Doping: The property of semiconductors that makes them most useful for constructing electronic devices is that their conductivity may easily be modified by introducing impurities into their crystal lattice. The process of adding controlled impurities to a semiconductor is known as doping. The amount of impurity, or dopant, added to an intrinsic (pure) semiconductor varies its level of conductivity. Doped semiconductors are often referred to as extrinsic. An intrinsic semiconductor has equal concentrations of electrons and holes.
Uses: Semiconductors are important in electronic technology. Semiconductor devices, electronic components made of semiconductor materials, are essential in modern consumer electronics, including computers, mobile phones, and digital audio players. Silicon is used to create most semiconductors commercially, but dozens of other materials are used.
Extra: A semiconductor (a.k.a. a chip) is a material such as silicon, which conducts electrical charges but not as well as metals such as copper and aluminum.
To recap: Chip = semiconductor = integrated circuit. Semiconductors are used in computers, DVD players, cell phones, household appliances, and video games, along with many other products.

Figure:
When electricity or light is applied to semiconductors, they change their state between conductive and non-conductive or reflective and non-reflective. The most significant semiconductor is the transistor, which in digital circuits works like an on/off switch. For analog applications, it may be an on/off switch as well, but is more likely used as an amplifier, taking in a low-voltage signal and outputting a higher voltage. See n-type silicon, doping and chip.


Conceptual View of a Transistor
In a certain type of transistor, the semiconductor material normally acts as an insulator. When it is pulsed with electricity, it becomes electrically conductive for that moment and acts like an electrical bridge.





Q.4. (e) Geothermal Energy
Definition: Energy obtained by tapping the earth’s underground reservoirs of heat, usually near volcanoes or other hot spots on the surface of the Earth.
Applications: Most geothermal resources are in regions of active volcanism. Hot springs, geysers, pools of boiling mud, and fumaroles are the most easily exploited sources. The ancient Romans used hot springs to heat baths and homes, and similar uses are still found in Iceland, Turkey, and Japan. Geothermal energy's greatest potential lies in the generation of electricity. It was first used to produce electric power in Italy in 1904. Today geothermal power plants are in operation in New Zealand, Japan, Iceland, Mexico, the U.S., and elsewhere.
Electricity generation: Three different types of power plants - dry steam, flash, and binary - are used to generate electricity from geothermal energy, depending on temperature, depth, and quality of the water and steam in the area.[4] In all cases the condensed steam and remaining geothermal fluid is injected back into the ground to pick up more heat. In some locations, the natural supply of water producing steam from the hot underground magma deposits has been exhausted and processed waste water is injected to replenish the supply. Most geothermal fields have more fluid recharge than heat, so re-injection can cool the resource, unless it is carefully managed.
Advantages: Geothermal energy offers a number of advantages over traditional fossil fuel based sources.
 From an environmental standpoint, the energy harnessed is clean and safe for the surrounding environment.
 It is also sustainable because the hot water used in the geothermal process can be re-injected into the ground to produce more steam.
 In addition, geothermal power plants are unaffected by changing weather conditions.
 Geothermal power works continually, day and night, providing baseload power.
 From an economic view, geothermal energy is extremely price competitive in some areas and reduces reliance on fossil fuels and their inherent price unpredictability.
 Given enough excess capacity, geothermal energy can also be sold to outside sources such as neighboring countries or private businesses that require energy.
 It also offers a degree of scalability: a large geothermal plant can power entire cities while smaller power plants can supply more remote sites such as rural villages.
Disadvantages: There are several environmental concerns behind geothermal energy.
 Construction of the power plants can adversely affect land stability in the surrounding region. This is mainly a concern with hot dry rock geothermal energy Enhanced Geothermal water into hot dry rock where no water was before.
 Dry steam and flash steam power plants also emit low levels of carbon dioxide, nitric oxide, and sulfur, although at roughly 5% of the levels emitted by fossil fuel power plants.
 Although geothermal sites are capable of providing heat for many decades, eventually specific locations may cool down.

Q.4. (f) Computer Virus
Definition: Computer program designed to copy itself into other programs, with the intention of causing mischief or damage.
Explanation: A virus will usually execute when it is loaded into a computer's memory. On execution, it instructs its host program to copy the viral code into any number of other programs and files stored in the computer. The corrupted programs may continue to perform their intended functions while also executing the virus's instructions, thus further propagating it. The infection may transfer itself to other computers through storage devices, computer networks, and on-line systems. A harmless virus may simply cause a cryptic message to appear when the computer is turned on; a more damaging virus can destroy valuable data. Antivirus software may be used to detect and remove viruses from a computer, but the software must be updated frequently for protection against new viruses.
Worms & Trojan Horses: Viruses are sometimes confused with computer worms and Trojan horses. A worm can spread itself to other computers without needing to be transferred as part of a host, and a Trojan horse is a file that appears harmless. Worms and Trojans may cause harm to either a computer system's hosted data, functional performance, or networking throughput, when executed. In general, a worm does not actually harm either the system's hardware or software, while at least in theory, a Trojan's payload may be capable of almost any type of harm if executed. Some can't be seen when the program is not running, but as soon as the infected code is run, the Trojan horse kicks in. That is why it is so hard for people to find viruses and other malware themselves and why they have to use spyware programs and registry processors.
Most personal computers are now connected to the Internet and to local area networks, facilitating the spread of malicious code. Today's viruses may also take advantage of network services such as the World Wide Web, e-mail, Instant Messaging and file sharing systems to spread, blurring the line between viruses and worms. Furthermore, some sources use an alternative terminology in which a virus is any form of self-replicating malware.

Q.4. (g) Pasteurization
Definition: Partial sterilization of a substance, especially milk or other beverages, by using heat to destroy microorganisms while leaving its chemical makeup unaltered. The process is named for Louis Pasteur, its originator.
Explanation: Pasteurization of milk requires temperatures of about 145 °F (63 °C) for about 30 minutes, or higher temperatures for shorter periods. The treatment destroys any disease-causing organisms (principally Mycobacterium tuberculosis) as well as organisms that cause spoilage. Pasteurization of milk destroys all pathogens, and although it will sour within a day or two, this is not a source of disease. It is achieved either by heating to 63-66 °C for 30 minutes (holder method), followed by immediate cooling, or (the high-temperature short-time process) heating to 71 °C for 15 seconds.














Q.7. (a) Energy
Definition: Capacity for doing work.
Forms of Energy: Energy exists in various forms — including kinetic, potential, thermal, chemical, electrical, and nuclear — and can be converted from one form to another.
Energy Converters: For example, fuel-burning heat engines convert chemical energy to thermal energy; batteries convert chemical energy to electrical energy.
Characteristics of Energy: Though energy may be converted from one form to another, it may not be created or destroyed; that is, total energy in a closed system remains constant. All forms of energy are associated with motion. A rolling ball has kinetic energy, for instance, whereas a ball lifted above the ground has potential energy, as it has the potential to move if released. Heat and work involve the transfer of energy; heat transferred may become thermal energy. See also activation energy, binding energy, ionization energy, mechanical energy, solar energy, zero-point energy.
Renewable Sources of Energy: The main five renewable sources of energy include:
1. Solar energy.
2. Wind energy.
3. Tidal or wave energy.
4. Hydroelectricity.
5. Biomass
How can our country come out of the present energy crisis? …

Q.7. (b) Ceramics
Definition: Ceramics are objects created from such naturally occurring raw materials as clay minerals and quartz sand, by shaping the material and then hardening it by firing at high temperatures to make the object stronger, harder, and less permeable to fluids. The principal ceramic products are containers, tableware, bricks, and tiles.
Types of Ceramic Materials: Ceramic materials can be subdivided into traditional and advanced ceramics.
(1) Traditional ceramics include clay-base materials such as brick, tile, sanitary ware, dinnerware, clay pipe, and electrical porcelain. Common-usage glass, cement, abrasives, and refractories are also important classes of traditional ceramics.
(2) Advanced materials technology is often cited as an enabling technology, enabling engineers to design and build advanced systems for applications in fields such as aerospace, automotive, and electronics. Advanced ceramics are tailored to have premium properties through application of advanced materials science and technology to control composition and internal structure. Examples of advanced ceramic materials are silicon nitride, silicon carbide, toughened zirconia, zirconia-toughened alumina, aluminum nitride, lead magnesium niobate, lead lanthanum zirconate titanate, silicon-carbide-whisker-reinforced alumina, carbon-fiber-reinforced glass ceramic, silicon-carbide-fiber-reinforced silicon carbide, and high-temperature superconductors. Advanced ceramics can be viewed as a class of the broader field of advanced materials, which can be divided into ceramics, metals, polymers, composites, and electronic materials.













Q.8. (a) Camera
Definition: A camera is a device that takes photos of images, either as a photograph or moving images known as videos or movies.
History: The term comes from the camera obscura (Latin for "dark chamber"), an early mechanism of projecting images where an entire room functioned as a real-time imaging system; the modern camera evolved from the camera obscura.
Components & Working: A camera generally consists of an enclosed hollow with an opening (aperture) at one end for light to enter, and a recording or viewing surface for capturing the light at the other end. A majority of cameras have a lens positioned in front of the camera's opening to gather the incoming light and focus all or part of the image on the recording surface. The diameter of the aperture is often controlled by a diaphragm mechanism, but some cameras have a fixed-size aperture. Cameras may work with the light of the visible spectrum or with other portions of the electromagnetic spectrum.
Camera’s Focus: Due to the optical properties of photographic lenses, only objects within a limited range of distances from the camera will be reproduced clearly. The process of adjusting this range is known as changing the camera's focus.
A Camera’s Resemblance in its Function with the Human Eye:












Q.8. (b) Plastics
Definition: Plastics are organic substances made up of huge molecules called polymers.
Constituents: Chemicals found in plastics include carbon, hydrogen, oxygen, and nitrogen. Chlorine, fluorine, sulfur, or silicon may also be present. To make the polymers more flexible or tougher, a plasticizer is added.
Types of plastics:
(1) Thermoplastics: Thermoplastics are formed from long linear chains of molecules (polymers). These polymers can be softened and when cooled regain a solid state. These plastics can be first formed as sheets, pellets, films, tubes, rods, or fibers. These forms can then be reheated and molded into other shapes. For example, nylon thread can be made into fabric. The various chemical and molecular properties of thermoplastics determine whether they are called nylon, polyester, polypropylene, polystyrene, polyethylene, polyvinyl chloride (PVC), or other names.
(2) Thermo-set plastics: Thermo-set plastics are different. These polymers are formed from two directions and produce three-dimensional networks of molecules, not linear chains. Such substances cannot be re-melted. They are formed through compression molding or casting. Thermo-set plastics include phenolic laminates (the original Bakelite), urethane, melamine, epoxy, acrylic, silicone, fluorocarbons, and others.
Uses of Plastics
Plastics are prolific and have many advantages over other heavier, easily corroded, breakable, or more expensive materials.
(1) Uses of thermoplastics:
The five most prevalent plastics are all thermoplastics and account for 90 percent of the plastics of the early twenty-first century. These include
polyethylene, used in all types of bags, diaper liners, agricultural covers, and milk and juice jugs;
polyethylene terephthalate (PET), used principally for soda bottles and videotapes;
polystyrene, used as clear packaging, as a foam (Styrofoam), or for furniture, toys, utensils, and dishes;
polypropylene, used for battery cases, crates, film, molded car parts, appliances, fish nets, and wire coating; and
polyvinyl chloride, used as a flexible substance in film, hoses, rainwear, and wall coverings, or as a rigid substance in pipes, buildings, and credit cards.
(2) Uses of Thermoset Plastics:
The most prevalent thermoset plastics are phenolics, used with formaldehyde and fillers in plywood, fiberglass, and circuit boards; and urea resins, used in polyurethane foam fillers.










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