Chemical laser and tunable laser.

In a chemical laser instead of atoms the molecules are brought in the metastable state by a chemical reaction. These lasers are very strong and efficient. In a chemical laser, hydrogen and fluorine gases combine to form the  hydrogen fluoride gas. It is used to obtain an infrared laser beam of nearly 2 MW power.

Another chemical laser is the carbon dioxide laser. It is used to obtain a laser beam of nearly 100w power. Its main application is in sergery to close he small blood vessels while cutting the tissues by the evaporation of water the through the infrared beam. In the industrial area carbon lasers of more power are used for cutting the metal sheets.

The other chemical lasers me the dye lasers in which organic dyes are used. The energy levels of molecules of these dyes close due to which are very Laser beam can be obtained from them in a continuous range of wavelength. The Wavelength range of these lasers is from the visible region to the infrared region. By changing the separation between the mirrors at the two ends of the resonant cavity, a dye laser can be tuned for the desired of wavelength range. This is why the dye lasers are also called the tunable lasers.

What is Dielectric ?

Dielectric- Material such as glass ceramics polymers and paper are non-conducting materials. They prevent flow of current through them. Therefore they can be used for insulative purposes when the main function of non-conducting materials is to provide electrical insulation they are called insulators. When non-conducting materials are placed in an electric field. they modify the electric field and themselves undergo appreciable changes as a result of which they act as stores of electrical chages. When charge storage is the main function the materials are called dielectrics. For a material to be a good dielectric, it must bw an insulator. Hence any insulator is a dielectric.

Physical process of depletion layer.

Physical Process of Depletion Layer- We know that a p-type materials has holes as majority carriers negatively charged impurity atoms called negative ions (or acceptor ions). The n-type material has free electrons as  majority carriers and positively charged impurity atoms called positive ions (or donor ions). When we combine these two materials, following process takes place-

(i)The holes from p-region diffuse to the n-region where they combine with the free electrons.
(ii) The free electrons from the n-region diffuse to the p-region where they combine with holes.
(iii) The diffusion of holes (from p-region to n-region) and free electrons (from n-region to p-region) takes place due to the reason that there is a difference of concentrations in the two regions. (iv) The diffusion of holes and electrons across the junction takes place for a short time. After a few recombination of holes and free electrons in the vicinity of the junction, a restraining force is automatically Setup This force is produced due to depletion région. which exists on either side of the junction. As result of this further diffusion of holes and free electrons from a one region to the other is stopped by this depletion layer.

Motion of charged particles in crossed electric and magnetic fields.

When Uniform electric and magnetic fields are perpendicular to ed oderand act over the same region they are said to be in crossed configuration. When electrons pass through the region, they are defected simultaneously both the fields. Let two charged plane parallel plates set up a uniform ele field E in the y-direction and a uniform magnetic induction B is also set up the same region between the plates in z-direction. The magnetic feld is sud to act into the page. The fields are so oriented that they are perpendicular to the direction of motion of electrons which is say, x-direction. Let a Step lectrons enter the crossed field configuration with a velocity v.
The electric field deflects the electrons upward where as the m field deflects them downward.
The force due to the electric field is and the force due to due to the electric field is -
FE=eE.

Limitetions of Geiger Muller.

One main disadvantages of G.M. counter is its dead time. Dead time refers to the time taken by the tube to recover between counts. it require about 200 IS for the tube to recover Ifa lot of particles enter the G.M. tube of rapid rate, the tube will not have time to recover and some particles may nd be counted.

History of Superconductivity.

Superconductivity is a state exhibited by many conductors when cooled below their superconducting transition temperatures. Superconductivity is one ofthe most fascinating physical phenomena having a vast potentiality in practical applications. A superconducting material exhibits zero electrical resistivity and complete diamagnetism. The superconducting state is influenced by temperature, magnetic field, and current. There exist critical values for these three parameters above which values the material passes into normal State.

In 1908, the Dutch Physicist Kammerlingh Onnes succeeded in his efforts to liquefy helium, Gaseous helium turned into liquid helium at 4.2K at atmospheric pressure. Using liquid helium as the coolant the variation of  electrical resistance of metals at low temperatures was studied by Chines In one theory, the electrical resistance of pure metals should decrease continuously and vanish at absolute zero temperature. In another theory it was expected to increase exponentially as temperature approaches 0K. However, in the year 1911, onnes discovered that the electrical resistance of highly purified mercury dropped abruptly to zero at 4.15 K. Sudden drop in resistivity was not in accordance with the expectations and was recognized by Onnes to be an emirelynew phenomenon. He called it superconductivity Subsequently super conductivity was discovered in lead. tin, zinc, aluminium and other metals as well as in a number of alloys.

What is Soler cell?

solar cell is a device which is used for converting radiation energy into electrical energy. These cells generate a voltage proportional to electromagnetic radiation intensity and are called the photovoltaic cells because of their voltage generating capability.
selenium and silicon are the most widely used materials for solar cells though gallium, arsenide, indium, arsenide, and cadmium sulphide are also used. The construction and cross-section of a typical power solar cell for use as an energy converter. The surface layer of p-type material is extremely thin so that light can penetrate to the junction. The nickel-plated ring around the p-type material is the positive output terminal and the plating at the bottom of the n-type material is the negative output terminal, Power solar cells are also available in flat strip for efficient coverage of available surface area.

Band theory of solids in solid state physics

On the basis of the classical free electron theory, electrical conduction Can occur in solid available. On the other hand, according a if free electrons are o band theory electrical conduction can take place in solid only if(i) a good number of free electrons are present and (ii) vacant levels are available immediately above the occupied energy levels Free electrons can absorb energy from the current source only inhere are unoccupied energy levels nearby gaining energy they jump into the empty levels giving rise to an electric current It describes that a partially filled band is required for causing electrica conduction.

Comparison between shell model and liquid drop model.

A comparative study between the single particles shell model and the liquid drop model according to Niels Bohr is that both are in conflict it each other In the shell model, it has been assumed that each nucleon moves in its orbit within the nucleus, independently of all other nucleons. The orbit determined by a potential energy function V(r). Each nucleon is regarded as an independent particle and the interaction between nucleons is considered to be a small perturbation on their action between the orbital nucleon and the rest is very weak in the liquid drop model,on the otherhand the nucleons are considered to interact strongly with each other so that the collective motions are possible. The following three examples speak infavour ofsuch collective motions-
(1) The phenomenon of nuclear fission which can be easily descr in terms of free vibrations of a liquid drop.
(2) The large values of electric quadruple moment in some nude cannot be accounted for on the single particle shell model. The discrepancy between the theoretical be explained only on de and experimental values can assumption that collective distortions nuclear core involving many of the nucleons also contribute to the quadruple moment.
(3) The third example is observed mean lines for ramna radiation of the electric quadruple type.
The observed lines are approximately 100 times shorter than estimated on the assumption that moves during the transition. This only one proton suggests that changes in the deformation of the core are involved.

What are salient features of liquid drop model of nucleus?

There are two important models proposed to explain the behavior and properties of the nucleus. They are liquid drop model and the shell model.
The liquid drop model was proposed by Niels Bohr in 1936, based on e external analogy between the nucleus and a liquid drop. Short range intermolecular forces operate in a liquid drop. The surface molecules at attracted to the inner molecules and the result is surface tension because of which the liquid drop takes spherical shape. The molecules in the liquid drop are in random motion and frequently collide with each other. The nudes possesses similar properties. The nucleons in a nucleus are in rapid motion and undergo frequent collisions. Each collision between nucleons involves an exchange of energy and momentum between them. If a certain amount of energy is imparted to the nucleus it gets excited me energy gets redistributed rapidly between the nucleons due to their mutual collisions. Some ofthe energy may be transferred to a surface nucleon. If energy of the nucleon is greater than its binding energy in the nucleus, the nucleon overcomes the nuclear forces and leaves the nucleus. The expulsion of a nuclear particle from the nucleus is similar to the evaporation of a molecule from a liquid drop.

Junction Breakdown

In case of reverse bias, a point is reached where application of too much negative case voltage will result in a sharp in the characteristic.
     At this point junction breakdown and current increases at a very rapid rate in a direction opposite to voltage region The reverse bias voltage that results in this dramatic change in character is called "Breakdown Potential" or " Zener Potential" and this sharp change in characteristics at any level is called zener region. It is found that once breakdown has occurred, very little further increase in voltage is required to increase the current to relatively high value. The junction itself offers almost zero resistance at this point.
The breakdown voltage depends on the width of the depletion region which, in turn, depend on doping level. There are two Dypes of breakdown:
(1) Zener Breakdown
(2) Avalanche Breakdown.

Why Si and Ge are used in semiconductors ?

Si and Ge are the two materials that have received the broadest range of interest in the development of semiconductor devices. The reasons for this are as follows:
(1) They can be manufactured to a very high purity level. In fact recent advances have reduced impurity levels in pure material to one part in 10 billion (1:10 000,000,000)
(2) The addition of one part of impurity (of the proper types) per million in a wafer of silicon material can change that material from a relativity poor conductor to a good conductor of electricity.
(3) Their characteristics can be altered significantly through the application of heat and light an important consideration in the development of heat and light sensitive devices.

Structure of ATOM

As you are aware, the atom is composed of three basic particles:
(a) Electrons
(b) Protons
(c) Neutrons 
Protons and Neutrons form the central portion ofthe atom which is called Nucleus while electrons move in approximately elliptic orbit about the nucleus. The mass of the protons and neutron is approximately same The difference between the two is that the proton is a positively charged particle and neutron is an electrically neutral particle.
          The electrons which revolve around the nucleus are very light in weight. An electrons is 1850 times lighter than a proton orneutron, this is because almost total mass of an is concentrated in its nucleus. Also electrons are negatively charged particles atom. The number of orbiting electrons are always equal to number of protons for any atom thus making atom electrically neutral.

What is fermi level ?

Fermi level is defined as the energy state or level which has a 50% probabilis of being filled by an electron.
For pure semiconductor, the Fermi Level lies midway between conduction band and valence band asshown in fig. At an absolute temperatureT=0 K, all energy states above the fermi level are empty and all energy states below fermi level are occupied. As the temperature increases some covalent band breaks up and such electrons go to the conduction band. Due to this, the fermi level shifts upward as the temperature increases.

Applications of Zener diode.

Applications of Zener Diode-
(i) It is used as a voltage regulator which gives a constant voltage from a source whose voltage may vary over suficient range.
(ii) It is used as a fixed reference voltage in transistor biasing circuits.
(iii) In waveshaping circuit, zener diode is used as limiter.
(iv) A Zener diode protect a meter movement or circuit against damage from an accidental application of excessive voltage.
(v) zener diode can produce a sudden change from low current to high current, so it is useful for switching operation.

What is optic axis ?

Optic Axis- Uni-axial crystals have a direction along which ordman and extra-ordinary rays propagate with the same velocity and without Separation. This direction is called the optic axis of the crystal. Any direction parallel to the optic axis is also an optic axis. Thus, an optic axis is direction a in the crystal and not a unique straight line passing through specific a set of points in the crystal. The optic axis is actually the axis of symmetry of the crystal. A ray of light propagating along the optic axis does not suffer double refraction, because the structure of the crystal is symmetrical about that direction.

What is Anisotropic material ?

Anisotropic Material- Material which exhibits double refraction phenomenon is known as anisotropic material. If the light is incident on a transparent anisotropic costal itis divided into two rays refracted with different velocities and in different directions.

What is Storege pool in data structure.

The storage pool contains all nodes that are not currently being used. This pool cannot be accessed by the programmer except through the getnode and feenode operations getnode removes a node from the pool whereas féénode returns a node to the pool. The most natural form for this pool to take is that of a linked list acting as a stack. The list is linked together by the new field in each node, The Remode operation removes the first node from this list and makes it available for use. The Renode operation adds a node to the front of the list, making it available for reallocation by the next getnode. The list of available nodes is called the available list.

Difference between an abstract data type specification and implementation

The abstract specification illustrates the role of an ADT as a purely logical definition of a new data type.
An ADT consist of two parts- a value defination and an operator defination. The value defination defines the collection of the value for the ADT and consist of two parts- a definition clause and a condition clause. Immediately following the value definition comes the operator definition. Each operator is defined as an abstract function with three parts - a header, the optional preconditions and the post conditions. The header specify any restrictions that must be setisfied before the operation can be applied. The post cordition specifies what the operation does.

Implementation-  an ADT means providing the procedure or production for each abstrct operation. The ADT instance are represented bt some concrete data struction that is manipulated by those procedure, according to the ADT's specification.

What is single processor implementation in data structure ?

Single Processor Implementation (Storage Areas)- When a subprogram is called in one processor, it must have a storage area; it must save the registers or whatevers else it will change, using the storage area also for its return address calling parameters, and local variables. As it returns, it will restore the registers and the other storage that it was expected to restore After the return it no longer needs anything in its local storage area.
In this way we implement subprogram calls by changing storage areas an action that takes the place of changing processors In these considerations it really makes no difference whether the subprogram is called recursively or not, providing that. in the recursive case, we are careful to regard two recursive calls as being different so that we do not mix the storage areas for me call with those ofanother, any more than we would mix storage areas for different subprograms one called from within the other.

What is digital circuit and system ?

A digital circuit is one in which the voltage levels assume a finite number of distinct values.
Digital circuits are often called switching circuits, because the voltage levels in a digital circuit are assumed to be switched from one value to another instantaneously, that is the transition time is assumed to be zero.
Digital circuits are also called logic circuits, because each type of digital circuit obeys a certain set of logic rules. The manner in which a logic circuit responds to an input is referred to the circuit's logic.
All of us are familiar with the impact of modern digital computers, communication systems, digital display systems, internet, e-mail, etc on society. One ofthe main of this revolution is the advent of integrated circuits (ICs ) which became possible because of the tremendous progress in emiconductor technology in recent years. Most of us may not be familiar ith the principles ofworking ofcomputers, communication systems, internet e-mail, etc. even though these have become an important part ofour daily life The operaton isbased m the ofthese sysems an many otersysems principles of digital techniques and these are referred to as digital systems.

Different source of water

we know that water is a main essential compound for living organism. The water which is used by living beings occurs from different sources of Water, basically there are two main sources of water which are follows-
1) Surface water--Water which is available from the earth surface is called surface water. It is generally clear and colourless and acidic in nature due to dissolved CO2 and organic matter. Surface water includes following types of water-

(a) Rain Water- Rainwater is obtained of evaporation from surface water, it is the purest form of natural water, during its downward Journey through the atmosphere it dissolved a considerable amount of industrial gases (like CO2 So2, No2 etc.) Rainwater is expensive to collect and irregular in supply.

(b) River Water- River water contain dissolved minerals like chlorides, sulphates bicarbonates of sodium magnesium, calcium and iron water from these sources now over the surface of land. The composition ofriver water not constant. In river water the greater is the amount of dissolved impurities. The amount of dissolved impurities depends on its contact of the soil.

(c) Lake Water-Lake water has more constant chemical composition. It has high quantity of organic matter but lesser amount of dissolved minerals. The chemical composition of lake water is constant.

(d) Sea Water- It is the most impure form of the natural water, because sea water contains various types of impurities. we know that all rivers join sea and throw in the impurities carried by them. There are many salts present in sea water. Bicarbonates of potassium magnesium and calcium and other harmful compounds  present in sea water.

2) Underground Water- Some part of rainwater which is reaches the inner surface of earth is called underground water mainly spring water and well water.
Generally spring and well water is clear in appearance due to the mering action of the soil, but this type of water contain moreover dissolved salts. Thus, water available from these sources contains high more hardness and organic impurities.

What is operating system ?

An operating system is an integrated set of programs that controls the resources such as CPU, memory, I/O devices etc., of a computer systemand provides its users with an interface or virtual machine that is more convenient to use that the bare machine.

An operating system is master control program that runs the computer and acts as a scheduler. It controls the flow of signals from CPU to various parts of the computer. It is first program loaded into the memory when the computer is tured on. Popular operating systems are MS-DOS, Windows and UNIX.

An operating system (also called as OS) supervises and provides services to computer users. It permits the computer to supervise its own operations by automatically calling in the applications programs and managing the data needed to produce the output desired by users. It isolates the hardware from the user. The functions provided by OS are transparent or invisible to the users.

Multimedia and Animation

Computers can be used to integrate two or more types of media, such as text, graphics, image, audio, and video, for the purpose of generation, storage, representation, manipulation ans access of multimedia information. Multimedia is one of the most commonly used terms in entertainment industry, which produces various entertainment products such as movies and video games.

Computer animation deals with the generation, sequencing, and display of a set of images to create an effect of visual change or motion, similar to a movie film (video). Animation is an important component of multimedia, because just as a picture is a powerful way to illustrate information, a small animation clip is even more powerful and useful for illustrating concepts, which involve movement.
For example, in the multimedia application meant for educating small children, an animation clip will be very effective in illustrating the difference in the movment of a horse during a gallop versus a walk. Several movies and advertisements now contain many visual tricks, which could never be accomplished without the aid of computers. For example, if you carefully watch the advertisements for detergent soaps/powders, toothpastes, insecticides for mosquitoes and cockroaches, etc., you will notice avenge in them, which cannot be videographed. These scenes are produced by using computer animation.

Ethics in Computing

Ethical conduct goes beyond merely adhering to laws. All professions have a code of ethics that broadly sets standards for professionals. Such ethical standards may not be covered by specific legislation. For example, what should you do if you are analyst or programmer responsible for a program that invades privacy ? Or how responsible are you if you create a software package that produces erroneous results ? After all, is it reasonable to expect software packages to be totally free of errors?

Of course, there are no simple answers to questions such as these. Many people with high ethical standards have argued against holding computer professionals totally responsible for their work, because the way a system is used may not be under the programmer's or analyst's control. Some people argue that, just as Alfred Nobel cannot be hold accountable for the immoral use of his invention of dynamite, computer professionals should not be hold accountable for programs that are used illegally or unethically.

As the debate over these ethical issues goes on, many leaders in the computing field believe that code of ethics is of primary importance and that it would be far better for professionals to police themselves before the government finds it necessary to pass laws.

Remote sensing and GIS

Remote sensing is the science of deriving information about the earth's land water areas form images acquired by using sensing devices operated from a remote location. It relies upon measurement of electromagnetic energy reflected or emitted from the features of interest.

The field of GIS and remote sensing has been referred to as the technology of today. The largest primary source of digital data for use in GIS is undoubtedly that created by remote sensing technology on board of sattellites and other aircraft's. Different schools of thought have different and varied definitions for geographic information system ( GIS). Tomlin defines a GIS as a configuration of computer and hardware and software specially designed for the acquisitions, maintenance and use of cartographic data. Burrough defines a GIS as a powerful set of tools for collecting storing and retrieving at will, transforming and displaying spatial data from the real world.

Thus, a GIS is a computer-assisted system for the acquisition, storage, analysis and display of geographically are spatially reference data.

Computer Gaming

Computers are also being used for playing video games. With the advent of multimedia, there has been a boom in the different type of video games available on computer systems. Sound and animation have been particularly important in these applications to make the games thrilling and exciting for the user. Because the sequence of events in such games depends on the action of the player, these programs are very interactive in nature.

Bio-informatics -Application of computer

Bio-informatics is the application of the computer technology to the management of biological information. Computers are used to gather, store, analyze and integrate biological and genetic information which can then be applied to gene-based drug discovery and development. The need for Bio-informatics capabilities has been precipitated by the explosion of publicly available genomic information resulting from the human genome project. The science of Bio-informatics, which is the melding of molecular biology with computer science, is essential to the use of genomic information in understanding human disease and in the identification of new molecular target for drug discovery. 

Health Care - one of the application of computer

Computers are also being used for planning and control purposes by health-care professionals. Computer equipment is used to monitor pulse rate, blood pressure and other vital signs. This leads to correct and fast diagnosis. Medical researchers are using computers as a tool in their search for cures of deadly diseases like cancer and AIDS.

E-business

E-business is about using Internet technologies to transform the way business processes are performed. Its most visible form is purchasing using PC and Internet. Every day, more companies and people gain access to the Internet, more purchases are executed electronically.

Custom-made Software

There are situations when none of the available pre-written software packages can meet the specific requirements of a user ( an organization or an individual ), either partially or fully. In such a situation, it becomes necessary to create a customized software package to satisfy the specific requirements. If the user has an in-hour software development team, the software package can be create in house. However, if such a team does not exist, the user must get it created by placing an order for it.

Database software

A database is a collection of records with fields. A database software is a set of one or more programs, which enables us to create a database, maintain it (i.e. add, delete and update its records), organize its data in disired fashion, and to selectively retrieve useful information from it.

Application Software

Application software or application packages are sets of one or more programs designed to carry out operations for a specified application. For example, every month a payroll package produces the payslips for the workers of a company.

Application software may be defined as software that provides an interface between the user and the system software to allow the user to perform specific tasks.

Some of the most commanly known application software are-

I) Word Processing software

II) Database software

III) Spreadsheet Software

IV) Graphics Software 

Utility Programs

Utility programs also called as utilities, are a set of programs, which helps users in system maintenance, and performing tasks of routine nature such as formatting of hard disks or floppy disks, taking backup of files, sorting of the records stored in a file, etc.

Communications software

In a network environment, communications software enables transfer of data and programs from one computer system to another.

Programming Language Translation

These are the system software, which transform the instructions prepared by programmers into a programming language into a form, which can be interpreted and executed by a computer system.

Operating Systems (pre-written software )

Every computer has an operating system software, which takes care of the effective and efficient utilization of the hardware and software components of the computer system.

System Software

A set of a one or more programs designed to operate, control and extend the processing capabilities of a computer system. These are general programs written to assist humans in the use of computer system and for making the operations of the computer system more effectively and efficient.

System software supports the following -
1) Running of other software.

2) Communicating with and controls peripheral devices such as printers, card readers, disk and tape etc.

3) Development of other application software.

4) Monitoring the effective use of various hardware resources such as memory, peripherals, CPU , etc.

The most common types of system are-

1) Operating systares
2) Programming Language Translator 3) Communications Software
4) Utility Programs

Voice Reproduction system

A voice reproduction system produces audio output by selecting an appropriate audio output from a set of pre-recorded audio responses. The set of pre-recorded responses include words, phrases or sentences spoken by human beings, music or alarms generated by musical instruments.
The application of voice reproduction system are-
I) Audio help for guiding how to operate a system. For example, bank uses voice reproduction system in ATM (automatic teller machines) to guide customers about transactions.
II) Automatic answering machines. For example, telephone enquiries for new telephone numbers in place of an old number, or vacancy status of a particular flight or train is taken care by an automatic answering machines.

Difference between inkjet and Dot Matrix Printer

Dot Matrix Printer and Inkjet Printer-
1) Inkjet printer is a non-impact printer while dot matrix printer is a impact printes.

2) Inkjet printer provide better printing quality than dot matrix printer.

3) Inkjet printers are less noisy than dot matrix printer.

4) Inkjet printer is expensive than dot matrix printer.

5) Inkjet printer resolution id good about 100 dots/cm while dot matrix printer has average resolution. 

Difference between Chain Printer and Drum Printer

Drum Printer and chain printer -
1)Chain printer uses a chain mechanism. There is one print hammer for each print position on the line. The characters are printed when the hammer presses the paper against the ribbon while in drum printer a metallic cylinder having column on the drum contains all the characters. Ad the drum rotates, each character that is to print reaches the appropriate position and a hammer then strikes that character.

2) Drum Printers are costly than chain printers.
3) In chain printers, chains may be changed easily while in drum Printers drums cannot be changed often.

Difference between Line printer and Character Printer

Character printer and line printer -
1) Line printers prints a line at a time while character printers prints a character at a time.

2) Line printer is faster than character printer.

3) Line printers are expensive than character printers.

4) Line printers are disigned for heavy printing applications and can print continuously for a few hours while character printers cannot be used continuously for more than one hour.

5) Line printers are called "heavy  duty" Printers while character printer are called "light duty " printers.

Speech Synthesizer

A speech synthesizer converts text information into spoken sentences. To produce speech , these devices combine basic sound unit called phonemes. From a given text information, sequence of words are combined into phonemes,  amplified and output through The speaker atteached to the system. Speech synthesizer are still in their infancy because they can produce only limited unique sounds with only limited vocal inflection and phrasing.

The application of speed synthesizer are -
1) For reading our text information to blind persons.

2) For allowing those persons, who cannot speak to communicate effectively.

3) For translation systems, which convert an entered text into spoken words in a selected language.

Voice Response Systems

A voice Response System has an audio-response device, which produces audio output. The output is temporary, soft copy output.
These are of two types-
(i) Voice Reproduction system

(i) Speech synthesizer

Screen Image Project

Screen Image Project is used for project information from a computer on to a large screen such as a cloth screen or a wall, so that it can be simultaneously viewed by a large group of people. A screen Image projector can be directly plugged to a computer system, and the presenter can make a presentation of a group of people by projecting the presentation material one after another on a large screen with the help of computer's mouse or keyboard. The presenter can also directly point to, mark, or edit certain portion of the content of the displayed material during the presentation to make the presentation more understandable.

Visual Display Unit (MONITOR)

Monitors are used as producing soft copy output. They display the generated output on a television like screen. A monitor is usually associated with a keyboard, and together they form a video display terminal (VDT ). A VDT ( also called terminal ) is input/output device. The keyboard is used for input to the computer and monitor is used to display the output from the computer.

The two basic types of monitors are cathode ray tube (CRT) and flat panel. The CRT monitors look like a television, and are used with non-portable computer systems. On the other hand, the flat monitors are thinner and lighter, and are used with portable computer system like notebook computer.

Advantages and disadvantages of laser printer compared to inkjet printer

Advantages-
I) It uses laser beam rather than squirting ink for printing which is a fast scheme.
II) The image quality is better than inkjet. 
III) It requires low maintenance as compared to others.


Disadvantages-
I) Generate high cost colour outputs.
II) It is costlier than inkjet printer.

Voice Recognition System or Voice Input Devices

Voice Recognition System or voice input Devices convert spoken words into electrical signals by comparing electrical patterns produced by the speaker's voice with a set of prerecorded patterns. It a machining is found, the computer accepts it as a part of its standard "Vocabulary".

Touch screen

A touch screen registers input , when a finger or other object cones in beam and ultrasonic acoustic wages. Infra-red beams crisscross the surface of the screen and when a light beam is broken, that location is recorded.

Magnetic Ink character reader (MICR)

MICR is widely used by banks to process large volumes of cheques and deposit forms, written everyday. A special ink called magnetic ink is used to write characters on the cheques and forms which are to be processed by a MICR. MICR is capable of reading characters on a paper written with magnetic ink. The magnetic ink is megnatized during the input process. The MICR reads the magnetic patterns of the written characters. To identify the character these patterns are compared with special pattern stored in the memory. Before cheque are issues to customers the identification number of the bank and the depositors account number are printed on the lower left-side of the cheques with the magnetic ink. The amount is printed on the lower right side of the cheque by the bank employee with the magnetic ink after the cheque is revived from the customer. When a cheque is entered into an MICR, it passes through a magnetic field. The iron oxide particles are magnetized under the magnetic field. The reader head reads the character written on the cheque with the magnetic ink. It interprets the characters and sends the corresponding data directly to the computer for processing.

Optical bar code readers

This method uses a number of bars or line of varying thickness and spacing between them, to indicate the desired information. Barcodes are used on most grocery items, cosmetics, paperback novels, etc. An optical bar reader can read such bars and convert them into electrical pulses to be processed by a computer. The most commonly used barcode is universal product code (UPC ). The UPC code uses a series of vertical bars of varying widths. These bars are detected as ten digits. The first five digits identifies the supplier or manufacturer of the item. The second five digits identifies individual product number. The code also contain a check digit, to ensure that the information read is correct or not.

Optical Mark reader ( OCR)

An optical mark Reader special marks such as squares or bubbles are prepared on examination answer sheets or questionnaires. The user fill in these squares or bubbles with soft pencil or ink to indicate their choice. These marks are detected by an optical mark Reader.
The OMR device has a high-intensity light that is directed as a beam at the sheet of paper being fed through it. The beam scans the sheet and detects number and location of the pencil markes. The data is then converted into electric signal for the computer.

Optical Character Reader ( OCR )

An optical character readers detects alphnumeric characters, printed or typewritten on paper. It may be a hand held scanner or a page scanner to detect light reflected from a line or from a page of the text. The change in the reflected light is converted too binary data which is sent to the processor.

Optical Scanners

The Optical Scanners are capable of reading information recorded on paper, employing light source and light sensors. The information to be typewritten information , hanf-written information, information coded as magnetic ink or pencil markes, or information coded as bars.
The following are the commonly used optical Scanners-
1) Optical Character Reader ( OCR )

2) Optical Mark Reader (OMR )

3) Optical Bar Code Readers

4) Magnetic Ink character reader (MICR )

Scanners

Scanners are a kind of input devices. They are capable of entering information directly into the computer. Important types of scanners are optical scanners and magnetic ink character readers.

Trackballs

Trackball is also a pointing device and contains a ball which can rotate in any direction. The user spins the ball in different directions to move the cursor on the CRT screen. The associated electronic circuitry detects the direction and the spin. The information is sent to the processor.

Joystick

A joystick is a positioning device. It is used to move the cursor position on a CRT screen. Its function is similar to that of a mouse. A joystick is a stick which has spherical ball at its lower end as well as at its upper end.

The lower spherical ball moves in a socket. The joystick can be moved right to left, forward or backward. The electronic circuitry inside the joystick detects and measures the displacement of the joystick from its cental position. The information is sent to the processor.

Mouse

A mouse is a pointing. As well as positioning device. It contain two or three buttons. As the rolls it on a flat surface, the mouse controls cursor movment on the screen. When the user presses one of the buttons , the mouse either markes a place on the screen or makes selections from data on the screen. It can be used for many applications, ranging from games to designing products with graphics.
It can be used as an alternative to keyboard or it can be used in combination with a keyboard to enhance input operations.

Light Pen

A light pen is a pointing device. It is used to select a displayed menu option on the CRT. It is a photosensitive pen like device. It is capable of sensing a position on the CRT screen surface, its photocell sensing element detection the light coming from the screen and the corresponding signals are sent to the processor. The menu is a set of programmed choice offered to the user.
A light pen can also be used for graphics work. A user can draw directly on the CRT screen with the light pens.

Punched Card and Card Readers

Punch card is a rigid piece of paper containing rows and column of numbers. It is put into a keypunch machine which place holes in to represent the data. This pattern of representing data as punched holes is known as Hollerith code. A card reader interpretes these holes to translate the punched information into a machine readable code and then send to the CPU for processing.
Punched cards are rarely used today. However, you may occasionally encounter in large companies such as public utilities, where they are still used for billing.

Keyboard

Programs and data are entered into a computer through a keyboard which is attached to a microcomputer or the terminal of a mini or large computer. It contains alphabets, digits, special character and some control keys. When a key is pressed, an electronic signal is produced which is detected by an electronic circuit called keyboard encorder. A keyboard encorder may be a special IC or a single-chip microcomputer. The function of an encorder is to detect which key has been pressed and send a binary code to the computer. The binary code may be an ASCII , EBCDIC , or HEX code .

A typical computer keyboard contains all the letters, number , symbols of a regular typewriter , plus other keys which may include numeric keys, special keys like control movement.

Ink-jet Printers

These are non-impact character printers, based on a relatively new technology. Ink-jet printers produce high quality output because the characters are formed by dozens of tiny ink dots. The document printer may contain multiple character styles and a variety of type sizes. Some models also allow for different colours of ink for multiple colour printing.

Dot-matrix Printers

These printers print each character as a pattern of dots. The print head comprises a matrix of tiny needles, typically seven rows with nine needles in each ( 9 x 7 matrix), which hammer out character in the form of patterns of tiny dots. The shape of each character, i.e. The dot pattern, is obtained from information held electronically in the printer.
The print quality of a dot matrix printer is inferior to that of a daisy wheel printer. But dot-matrix printer are faster than letter -quality printers in the range of 40 to 250 characters per second.

Letter-quality Printers

These printers use a print wheel font known as a daisy wheel. Each petal of the daisy wheel has a character embossed on it. A motor spins the wheel at a rapid rate.
A print hammer strikes it to produce the output. Daisy wheel printers are impact printers. Their output resembles a typed output and they are noted for their print quality. The speed of these letter-quality printers normally range from 10to 50 characters per second.

Page Printers

These are very high speed non impact printers, which can produced documents at speed of over 20,000 lines per minute. Electronics, xerography, lasers, and other technologies have made these high-volume systems possible. These techniques, called electro-photographic techniques, have developed from the paper copier technology.

Band Printers

Band printers are just like chain printers. They contain fast rotating scalloped steel print band, in place of a chain. Hammers strike the ribbon and the paper against the character to be print. Some printers can print upto 3000 lines/min.

Chain Printers

Chain printers use a rapidly rotating chain which is called is character font. The printers receive all the characters to be printed in one line from the processor. A chain may contain more than one character set. When the desired character comes in the print position, the hammer strikes the ribbon and the paper against the character. Its speed lies in the range of 400-2400 lines per minute.

Drum Printers

A drum printer consists of a solid, cylindrical drum that has raised characters in bands on its surface. There are as many bands as there are printing positions. Each band contain all the possible characters. The drum rotates at a rapid speed. For each possible print position, that is, opposite to each band of the drum, there is a print hammer located behind the paper. These hammer strike the paper, along with the inked ribbon.
Typical speeds of drum printers are in range of 300 to 2000 lines per minute. 

Laser printer

Laser printers works in the same manner as copy machines. A laser beam creates electrical charges that attract toner to from an image and transfer it to paper. Laser printers come in a variety of sizes, generally the large and faster the priter, the more expensive it is. Large laser printers used on mainframes and minicomputers where high-quality graphic output is required. Small, "personal" laser printers are suitable for home use. The laptop needs to have a built-in infrared transmitter installed, but no cable or no wires are required. Hewlett-Packard recently brought out of a wireless printer.

Characteristics of Computer and its Limitations.

The characteristics of computer are as follows-
(i) Speed - computer is a very fast device. It can perform in a few seconds the amount of work that a human being can do in an entire year. A computer can add and subtract numbers, compare letters to determine alphabetic sequence, move and copy numbers and letters. The speed varies from a few microseconds to nanoseconds.
(ii) Accuracy - Computer are very accurate. They can perform their hundreds of thousands of operation with great accuracy as their circuits have no machanical parts to wear and malfunction.
(iii) Reliability- Computer output is generally very reliable, subject to the condition that the input data entering the computer should be correct and the program of intructions should be reliable and correct. Incorrect input data and unreliable programs give us computer error and wrong results.
(iv) Storage capacity - Various computer media can store millions of character of data in a condensed form.
(v) Intangible benefits - There are many companies that utilize computers for intangible benefits such as flexibility, ability to accomodate growth and the psychological factor that may give  them a competitive edge in attracting consumers to buy their products or services.
(vi) Reduction cost - The cost of computer equipment has dropped drastically over the years.
(vii) Diligence - A computer is free from monotony, tiredness, lack of concentration, etc. And hence can work for hours together without creating any error and without grumbling.
(viii) Versatility - Versatility is one of the most wonderful feature about the computer. It is preparing the result of particular examination, the next moment it is busy for preparing electricity bills.
Computer Limitations - The computer is one of the most powerful tools ever developed. The man who was treated for pneumonia and then charged by the hospital's computer for the use of the delivery room and nursery. Such " computer failures" may be amusing. But most such foul-ups happed because people fail to consider some basic computer limitations. Without reliable programs and sounds logic, no computer system will perform adequately. 

What is a computer ?

A computer may be defined as ab electronic machine that can solve problem by accepting data, performing certain operations and presenting the result of those operations under the direction of detailed step-by-step instructions. Such a set of sequenced instructions, which cause a computer to perform particular operations, is called a program. 

Explain liquid drop model of atomic nucleus.

Explain liquid drop model of atomic nucleus.
Explanation-
According to this model a necleus can be assumed to be like a liquid drop for the following reasons-
(i) The stable necleus is spherical in shape due to symmetrical surface tension forces.
(ii) Such as the surface tension forces act on thevsurface of the liquid-drop similarly a potential barrier to surface of the nucleus acts.
(iii) The nuclear force are short range forces. Similarly, in liquid drop, the intermolecular forces are short range forces.
(iv) The density of liquid drop is independent of its volume. Similarly the density of nucleus is independent of its volume.
(v) On rising the temprature of liquid the molecules evaporate. Similarly, when energy is given to the neucleus a compound nucleus is formed which emits nucleons almost immediately . 

History of superconductivity

Superconductivity is a state exhibited by many conductors when cooled below their superconductivity transition temperature. Superconductivity is one of the most fascinating physical phenomena having a vast potentiality in practical application. A superconductor material exhibits zero electrical resistivity and complete diamagnetism. The superconducting state is influenced by temperature, magnetic field, and current. There exist critical values for these three parameters, above which values the material passes into normal state.   

What is a LASER ?

The word LASER is the short of light amplification by stimulated emission of radiation. Laser is that device is which an intense, monochromatic, coherent and uni-directional light beam is obtained. It was discovered in 1950, by Townes and Shallow.
Thus, a Laser produces a light beam in which all the waves are of same frequency.  all waves are in same phase and all waves travel in a definite direction

What is Newton's Rings

When a Plano-convex lens with its convex surface is placed on a plane glass plate, an air film gradually increasing thickness is formed between the two. The thickness of the film at the point of contact is zero. If monochromatic light is allowed to fall normally, and the film is viewed in reflected light , alternate dark and bright concentric rings with their center dark is formed between the lens and glass plate are seen. Since the phenomenon was described by Newton that is way the rings are known as Newton's Rings after his name.

Explain the Interference of Light.

When two light waves superimpose, then the resultant amplitude ( or intensity ) in the region of superposition is different then the amplitude of individual waves. this modification in distribution of intensity in the region of superposition is called inerteference. 
When the resultant amplitude is the sum of the amplitudes due to two waves, the interference is known as constructive interference and when the resultant amplitude is equal to the difference of two amplitude, the interference is known as destructive interference.


Types of interference-
i) Division of Wavefront
ii)Division of Amplitude

What is core type transformer ?

Constructionally there are rwo types of transformers i.e. Core type transformer and Shell type transformer. There are differ from each other by the manner in which the winding are wound around the magnetic core.
Core type transformer- in Core type transformers , the windings surround a considerable part of the core, i.e. The half turns of primary and secondary windings are placed on each limb (core).
Generally, circular coils are used in core transformer because of their mechanical strengh. Such cylindrical coil are wound in helical layer with the different layers insulated from each other by paper, cloth, micarta board or cooling ducts. Figure shows the diagram of Core type transformer.

What is Compton Effect?

In 1921, Professor A.H. Compton discovered that whrn a mono-chrometic beam of light of high frequency radiation ( X-rays, Y-rays, etc.) is scattered by a substance, the scattered radiation contain two components
-One having a lower frequency or greater wavelength and the another having the same frequency or wavelength.
The radiation of of unchanged frequency in the scattered beam is knows as unmodified radiation while the radiation of lower frequency is called as modified radiation.
And the difference in wavelength is known as Compton Effect.

Zener breakdown

ZENER BREAKDOWN
In this case breakdown occurs in junctiins, which are heavily doped. When the reverse voltage is increased , the electric field at the junction also increses. A strong electric field causes a covelent bond to break from the crystal structure. As a result a large number of minority carriers are generated and a large current flows though the junction.

What are intrinsic and extrinsic semiconductors ?

The semiconductors are of mainly two types-

(i) intrinsic semiconductor - A semiconductor, which is in its extremely pure form , is known as an intrinsic (or pure) semiconductor. The nature of semiconductors is such that even a small amount of certain impurities can change their electrical properties drastically. It is due to this fact, that a semiconductor would not be called truly intrinsic, unless the impurity level is very small .
The silicon and germanium are two most widely used intrinsic semiconductors.

(i) Extrinsic semiconductors- When a small quantity of impurity is mixed in a pure or intrinsic semiconductor is called the extrinsic semiconductors. The conductivity of resultant crystal depends on the nature and quantity of the impurity added . Depending upon the nature of impurity added in intrinsic semiconductor.
The extrinsic semiconductor are of two types-
    (a) N- type or doner
    (a) P- type or acceptor.

What is semiconductor ?

The materials, whose electrical properties lie between those of conductors and insulators, are know as semiconductor.
The exampels of such materials are-
»cadmium sulphides(CdS),
«gremanium(Ge),
»silicon(Si),
«gallium arsenide(GaAs),
»lead telluride  etc

In terms of energy bands , the semiconductors may be defined as those materials, which at room temperature, have

(i) Partial filled conduction band
(ii)Partial filled valenced band

In semiconductor, at absolute zero temperature there are no electrons in the conduction band and the valence band is completely filled. Thus semiconductors behaves like perfect insulators at 0°K.
However, as the temperature increased, the width of energy gap reduces. Consequently, some of the electrons jump into conduction band and semiconductor show some conductivity. It is thus obvious, that the conductivity of semiconductor increase in temprature.

mp board schools in indore

There are only limited schools present in indore which are affi. to mp board . now a days status of mp board is going down and down which is the main reason of decrease in number of mp board schools in indore . all the students who have more than 60 percent is only getting admission in cbse affi. schools or otherwise in mp board school he or she is forced to take admission .