Supercomputers
The term supercomputer does not refer to a specific technology, nut to the fastest computing engines available at any give time. Super computers typically run military and scientific applications, although their use of commercial applications.
Mainframe
Mainframe remains popular in large enterprise for extensive computing applications that are accessed by thousands of users. Mainframe are less powerful and generally less expensive than supercomputer.
Minicomputers
are relatively small inexpensive and compact computers that perform the same functions as mainframe computers, but to a more limited extent. These computer are designed to accomplist specific taskes such as process control, scientific research and engineering applications
Microcomputer
Are the smallest and least expensive category of general purpose computers They can be sub divided into four classifications based on their size desktop thin clients notebooks and laptops.
Friday, May 28, 2010
Carrer in IT
Programmer
Programmer are IS professionals who modify existing computer programs or write new programs to satisfy user requirments,
Systems Analyst/ Developers
System analyst are information systems professionals who specialize in analyzinf and designing information systems.
System Operations Specialist
System operations specialist keep systems up and running and many have subspecializations with particular types of computing hardware(eg. mainfrane)
Business Analyst
A business analyst has IT experience and an in-depth knowledge of the organization's business processes. He or she is ofter heavily involved with the development of new information systems and acts as a translator between IS developers and users.
Database Administrator
Data are ab extremely valuable organizational asset for both day to day operations and strategic objectives. Database administrator typically have considerable experience and training in one or more types of database software and hardware.
Programmer are IS professionals who modify existing computer programs or write new programs to satisfy user requirments,
Systems Analyst/ Developers
System analyst are information systems professionals who specialize in analyzinf and designing information systems.
System Operations Specialist
System operations specialist keep systems up and running and many have subspecializations with particular types of computing hardware(eg. mainfrane)
Business Analyst
A business analyst has IT experience and an in-depth knowledge of the organization's business processes. He or she is ofter heavily involved with the development of new information systems and acts as a translator between IS developers and users.
Database Administrator
Data are ab extremely valuable organizational asset for both day to day operations and strategic objectives. Database administrator typically have considerable experience and training in one or more types of database software and hardware.
Business in the information age
PRESSURES
1) Global competition for trade and for labor
Low labor costs make chineses firms attractive as partners in joint manufacturing ventures
2)Changing Work force
An intresting number of females, single parents, minorities, and physically challenged persons work today in all types of postions. More employees than ever before prefer to defer retirement. It is easing the integration of these various employees inot the traditional workforce.
3)Customer orientation
Customer sophistication and expectations increses as customers become more knowledgeable about the availability and quality of products and services. Customers are demanding ever-more detailed information about products and services. They want to know what feature warranties are available.
4)Information overload
The Internet and other telecommunications nteworks increase the amount of information available to organization and individuals. The amount information available on the Internet more that doubles every year and most of it is free.
5)Social responsibility
Social issues affecting organizations range from the state of the plysical environment. to non discriminatory employment practices, to the spread of infectioud diseases and other health concerns. Failure to accept social responsibility can result in employee dissatisfaction and trunover, a tarnished corporate reputation with the public, and in some cases, governmental samctions.
ORGANIZATIONAL RESPONSES
1) Strategic systems
Organizations seek to implement systems that will significantly impact the organization's operations, sucess or survival. Such strtegic systems provide organizations with strange advantages in meeting organizational objectives, enabling them to increase their market share, to better negotiate with their suppliers, or to prevent competitord from entering their markets. There are a variety of IT-supported strategic systems.
2)Customer focus and service
Organization must may more attentions to customers and their preferences. Sometimes such an approach even involves reengineering the organization to better meet customer demands. This can be done in part by changing manufacturing process from mass production to mass customization. In mass production, a company produces a large quantity of titems that are manufactured to fit the desires of each customer. Information technology supports mass customization.
3)Continuous improvement efforts
In response to business pressures, many firms also make continous efforts to improve their productivity and quality.
4)Business alliances
In response to some of the competitive pressures of the global economy, many firms are realizing that alliances with other firms, even competitors, can be very beneficial.
1) Global competition for trade and for labor
Low labor costs make chineses firms attractive as partners in joint manufacturing ventures
2)Changing Work force
An intresting number of females, single parents, minorities, and physically challenged persons work today in all types of postions. More employees than ever before prefer to defer retirement. It is easing the integration of these various employees inot the traditional workforce.
3)Customer orientation
Customer sophistication and expectations increses as customers become more knowledgeable about the availability and quality of products and services. Customers are demanding ever-more detailed information about products and services. They want to know what feature warranties are available.
4)Information overload
The Internet and other telecommunications nteworks increase the amount of information available to organization and individuals. The amount information available on the Internet more that doubles every year and most of it is free.
5)Social responsibility
Social issues affecting organizations range from the state of the plysical environment. to non discriminatory employment practices, to the spread of infectioud diseases and other health concerns. Failure to accept social responsibility can result in employee dissatisfaction and trunover, a tarnished corporate reputation with the public, and in some cases, governmental samctions.
ORGANIZATIONAL RESPONSES
1) Strategic systems
Organizations seek to implement systems that will significantly impact the organization's operations, sucess or survival. Such strtegic systems provide organizations with strange advantages in meeting organizational objectives, enabling them to increase their market share, to better negotiate with their suppliers, or to prevent competitord from entering their markets. There are a variety of IT-supported strategic systems.
2)Customer focus and service
Organization must may more attentions to customers and their preferences. Sometimes such an approach even involves reengineering the organization to better meet customer demands. This can be done in part by changing manufacturing process from mass production to mass customization. In mass production, a company produces a large quantity of titems that are manufactured to fit the desires of each customer. Information technology supports mass customization.
3)Continuous improvement efforts
In response to business pressures, many firms also make continous efforts to improve their productivity and quality.
4)Business alliances
In response to some of the competitive pressures of the global economy, many firms are realizing that alliances with other firms, even competitors, can be very beneficial.
Problems with Tradional Data base approach
Data Redundancy
As applications and their data files were created by different programmer over a period of time, the same piece of information could be duplicated in several places. Resulting in overconsuming of space
Data inconsistency:
Means that the various copies of the data no longer agree.
Data Isolation:
It also leads ro difficulty in accessing data from different applicatiob
Security:
is difficult to enforce in the file environment beacuse new applications may be added to the system on an ad-hoc basis and with more applications more people have access to data
As applications and their data files were created by different programmer over a period of time, the same piece of information could be duplicated in several places. Resulting in overconsuming of space
Data inconsistency:
Means that the various copies of the data no longer agree.
Data Isolation:
It also leads ro difficulty in accessing data from different applicatiob
Security:
is difficult to enforce in the file environment beacuse new applications may be added to the system on an ad-hoc basis and with more applications more people have access to data
Programming language
Machine Language
is the lowest level computer language, consisting of the internal representation of instructions and data. This machine code-the actual instructions understood an directly executablr by the central processing unit-- is composed of binary digits.
Assembly Language
is the next level up from machine language. It is still considered a lower level language but is more user friendly because it represents machine language instructions and data locatioins in promary storage.
Procedural Language
are the next step in the evolution of user-oriented programming languages. They are also called third-generation languages or 3GLs. Procedural languages are much closer to so-called natural language and therefore are easier to write read and alter
Nonprocedural Language
allows the user to specify the desired result without having to specify the detailed procedures needed for achiveing the result. These languages are fourth-generation languages.
Natural Programming Languages
NPL are the next evolutionary steps. They are sometimes know as fifth generation languages. nMost of these language are still experimental and have yet to be widely adopted by industry
is the lowest level computer language, consisting of the internal representation of instructions and data. This machine code-the actual instructions understood an directly executablr by the central processing unit-- is composed of binary digits.
Assembly Language
is the next level up from machine language. It is still considered a lower level language but is more user friendly because it represents machine language instructions and data locatioins in promary storage.
Procedural Language
are the next step in the evolution of user-oriented programming languages. They are also called third-generation languages or 3GLs. Procedural languages are much closer to so-called natural language and therefore are easier to write read and alter
Nonprocedural Language
allows the user to specify the desired result without having to specify the detailed procedures needed for achiveing the result. These languages are fourth-generation languages.
Natural Programming Languages
NPL are the next evolutionary steps. They are sometimes know as fifth generation languages. nMost of these language are still experimental and have yet to be widely adopted by industry
Computer Memory
Primary Storage
or main memory as it is sometimes called stores for very brief periods of time three types of information: data to be processed ny the CPU, instructions for the CPU, as how to process the data and operating system programs that manager various aspects of the computers's operation.
Registers.
Registers are part of the cpu . They have the least capacity, storing extremely limited amounts of instructions and data only immediately before and after processing.
Random access memory
It stores more information than the registers and is farther away from the CPU, but it stores less than secondary storage and is much closer to the CPU than is Secondary storage. RAM is temporary and volatile
Cache memory
It is a type of high speed memory that a processor can access more rapidly than main memory. Cache memory is a place closer to the CPU where the computer can temporarily store blocks of instructions used most often.
Read- only memory
is the place( atype of chip) where certain critical tinstructions are safeguarded. ROM is not volatile and retain these instructions when the power to the computertruned off. The read-only designation means that these instruction can be read only by the computer and can not be changed by user.
SECONDARY STORAGE
Magnetic media
Magnetic diskettes
Optical Storage
Memory cards
or main memory as it is sometimes called stores for very brief periods of time three types of information: data to be processed ny the CPU, instructions for the CPU, as how to process the data and operating system programs that manager various aspects of the computers's operation.
Registers.
Registers are part of the cpu . They have the least capacity, storing extremely limited amounts of instructions and data only immediately before and after processing.
Random access memory
It stores more information than the registers and is farther away from the CPU, but it stores less than secondary storage and is much closer to the CPU than is Secondary storage. RAM is temporary and volatile
Cache memory
It is a type of high speed memory that a processor can access more rapidly than main memory. Cache memory is a place closer to the CPU where the computer can temporarily store blocks of instructions used most often.
Read- only memory
is the place( atype of chip) where certain critical tinstructions are safeguarded. ROM is not volatile and retain these instructions when the power to the computertruned off. The read-only designation means that these instruction can be read only by the computer and can not be changed by user.
SECONDARY STORAGE
Magnetic media
Magnetic diskettes
Optical Storage
Memory cards
It support at diffferent organizational levels
Strategic decisions
are usually made by top managment these are relatively long term planning decisions that deal with the organization's objectives as a whole and the allocation of resources to achive these objectives.
Tactical or managerial decisions
are made by middle managers, who prepare short-term plans, procedures, and policies with which to begin implementing the organization's long term strategies. MISs provide the primary support at this level, along with some types of DSS
Operational decisions
are made by line managers and operators. These are the day-to-day decisions that aim to keep the organization's operations moving smoothly. TPSs typically capture the operational information relevant for decision making this level.
Pyramin diagram
Strategic System-----------Top Managers
Staff Support------------------------Knowledge workers, Professionals
MAnagerial systems--------------------------------Middle Managers
Operational System-------------------------------------------Line managars, operators
Office automation and Communication system-----------------------Clerical Staff
are usually made by top managment these are relatively long term planning decisions that deal with the organization's objectives as a whole and the allocation of resources to achive these objectives.
Tactical or managerial decisions
are made by middle managers, who prepare short-term plans, procedures, and policies with which to begin implementing the organization's long term strategies. MISs provide the primary support at this level, along with some types of DSS
Operational decisions
are made by line managers and operators. These are the day-to-day decisions that aim to keep the organization's operations moving smoothly. TPSs typically capture the operational information relevant for decision making this level.
Pyramin diagram
Strategic System-----------Top Managers
Staff Support------------------------Knowledge workers, Professionals
MAnagerial systems--------------------------------Middle Managers
Operational System-------------------------------------------Line managars, operators
Office automation and Communication system-----------------------Clerical Staff
Information System
Information system collects, processes, stores, analyzes, and disseminates information for a specific purpose. Like any other system, an information system includes inputs(data, instructions) and outputs(reports, calculations). It processes the inputs and produces outputs that are sent to the users or other system.
Data: are raw facts or elementary descriptions of things, events, activities, and transactions that are captured, recorded, stored and classified but not organized to convey any specific meaning. example grade point average, bank balance
Information: it is a collection of facts(data) organized in some manner so that they are meaningful to recipient. example student name with grade point average, customer name with bank balance.
Knowledge: consist of information that has been organized and processed to convey understanding, experiences, accumulated learning or expertise as it applies to a current business problem or process.
A computer based information system is an information system that used computer and telecommunication s technology to perform its intended task
Components of an Computer based information system
The compinents of an information system are hardware, software, database, net-works, procedures and people.
Hardware is a set of device sucs as a processor, monitor, keyboard and printer that accept data and information, process them and display them.
Software is a set of computer program that enable the hardware to process data.
A database is an organized collection of related files and records that stores data and the association among them.
A networks is a connecting system that permits the sharing of resources among different computers.
Procedures are the strategies, policies, method and rules for using the information system
The most important element in information systems is people, those persons who work with the information system or use its output
Cababilities of information system
1) Provide fast and accurate transaction processing
Every event that occurs in a business is called a transaction. Transactions include the sale of a unit of goods, a pay-check issued, a bank deposit, a course grade registered and so on. These data nust be captured accurately and quickly. This process is called transaction processing. A good example of transaction processing system ins point of sale.
2)Provide large-capacity, fast-access storage
Information systems must provide both enormous storage for corporate data, and also fast access to those data.
3)Provide fast communications(machine to machine, human to human)
Networks enable organozational employees and computers to communicate almost instantly around the world. High-transmission capacity networks(those with high bandwidths) make fast communications possible. In addition they allow data, voice, image, documents, and full-motion video to be transmitted simultaneously
4)Reduce information overload
Information systems(particularly networks) have contributed to managers having too much information. For example, the amount of sult, managers can feel drowned in information and unable to make decisions efficiently and effectively. Information systems can be designed to reduce this information overload.
5)Provide support for decision making
Decision support systems help decision makers across an organization and at all levels of the organization. Therefore, employees at lower organizationals levels have the authority and responsibility to make more and larger decisions than ever before.
Strategic use of information system
The forces that shape the level and type of competition in any industry include the relative power of buyers and suppliers, threats from substitute products and services, and the ease or difficulty with which new competitors can enter the industry. BAsic competitive strategies emphasize cost reduction and product differentiation. In addition, the value chain enables companies to understand and optimize the discrete steps involved in the manufacture of a product or the provision of a service, so as to add value to their products by improving quality and efficiency at every steps. These business concepts can be used to generate a series of questions about IT whose answers can shape an organization's competitive strategy. In general, IT give strategic competitive advantage through addressing and sometimes altering the nature of strategic competitive advantage through addressong and sometimes altering the nature of strategic force in industry, as well as advancing strategies based on cost and product differentiation
Major Is function
# Initiating and designing specific strategic information systems
# Infrastructure planning, development, and control
# Incorporating the Internet and e-commerce into the business
# Educating the non-IS managers about IT
# Supporting end-user computing
# Partnering with the executive level that runs the businerr
Data: are raw facts or elementary descriptions of things, events, activities, and transactions that are captured, recorded, stored and classified but not organized to convey any specific meaning. example grade point average, bank balance
Information: it is a collection of facts(data) organized in some manner so that they are meaningful to recipient. example student name with grade point average, customer name with bank balance.
Knowledge: consist of information that has been organized and processed to convey understanding, experiences, accumulated learning or expertise as it applies to a current business problem or process.
A computer based information system is an information system that used computer and telecommunication s technology to perform its intended task
Components of an Computer based information system
The compinents of an information system are hardware, software, database, net-works, procedures and people.
Hardware is a set of device sucs as a processor, monitor, keyboard and printer that accept data and information, process them and display them.
Software is a set of computer program that enable the hardware to process data.
A database is an organized collection of related files and records that stores data and the association among them.
A networks is a connecting system that permits the sharing of resources among different computers.
Procedures are the strategies, policies, method and rules for using the information system
The most important element in information systems is people, those persons who work with the information system or use its output
Cababilities of information system
1) Provide fast and accurate transaction processing
Every event that occurs in a business is called a transaction. Transactions include the sale of a unit of goods, a pay-check issued, a bank deposit, a course grade registered and so on. These data nust be captured accurately and quickly. This process is called transaction processing. A good example of transaction processing system ins point of sale.
2)Provide large-capacity, fast-access storage
Information systems must provide both enormous storage for corporate data, and also fast access to those data.
3)Provide fast communications(machine to machine, human to human)
Networks enable organozational employees and computers to communicate almost instantly around the world. High-transmission capacity networks(those with high bandwidths) make fast communications possible. In addition they allow data, voice, image, documents, and full-motion video to be transmitted simultaneously
4)Reduce information overload
Information systems(particularly networks) have contributed to managers having too much information. For example, the amount of sult, managers can feel drowned in information and unable to make decisions efficiently and effectively. Information systems can be designed to reduce this information overload.
5)Provide support for decision making
Decision support systems help decision makers across an organization and at all levels of the organization. Therefore, employees at lower organizationals levels have the authority and responsibility to make more and larger decisions than ever before.
Strategic use of information system
The forces that shape the level and type of competition in any industry include the relative power of buyers and suppliers, threats from substitute products and services, and the ease or difficulty with which new competitors can enter the industry. BAsic competitive strategies emphasize cost reduction and product differentiation. In addition, the value chain enables companies to understand and optimize the discrete steps involved in the manufacture of a product or the provision of a service, so as to add value to their products by improving quality and efficiency at every steps. These business concepts can be used to generate a series of questions about IT whose answers can shape an organization's competitive strategy. In general, IT give strategic competitive advantage through addressing and sometimes altering the nature of strategic competitive advantage through addressong and sometimes altering the nature of strategic force in industry, as well as advancing strategies based on cost and product differentiation
Major Is function
# Initiating and designing specific strategic information systems
# Infrastructure planning, development, and control
# Incorporating the Internet and e-commerce into the business
# Educating the non-IS managers about IT
# Supporting end-user computing
# Partnering with the executive level that runs the businerr
Wednesday, May 26, 2010
Interference:
When teo light easves travels in a same region, then there will be change in intensity due to superposition of light waves. This phenomenon is called interference. In other world non uniform distribution of energy when two light source super impose.
COndition for maxima and minima
Derive an expression for intensity on different points
let us consider two light waves travelling in a same region
let, y1 = asinwt ------1
y2 = ain(wt + theta)--------2
be the equation of two waves. We considered same amplitude, angular velocity but slightly different phase.
Here phase difference = theta
Now, the resultant wave can be given as
y = y1 + y2
= asinwt + asin(wt + theta)
=a(sinwt + sin(wt + theta))
y=(2acos(theta/2)*(sinwt+(theta/2))-------3
here, A = 2acos(theta/2)
We know intensity is directly proportional to A^2
therefor I directly porportional to A^2
I = A^2
I = 4a^2(cos(theta/2))
for maxima,
cos^2(theta/2) = 1
cos(theta/2)=+-1
cos(theta/2) = cos(n(pie)), n = 0,1,2....
or theta/2 = n(pie)
therefore theta = 2npie
here theta phase difference = lamda/2pie * theta phase difference = n*lamda
for minima cos^2(theta/2) = 0
or cos(theta/2) = 0
cos(theta/2) = cos(2n+1/2)pie
theta = (2n+1)pie
corresponding path difference
= lamda/2pie *(2n + 1)/2*pie
=(2n+1)/2 * lamda
maximum point 0, lamda,2lamda,3lamda
minimum points lamda/2 ,3/2lamda 5/2lamda
COndition for maxima and minima
Derive an expression for intensity on different points
let us consider two light waves travelling in a same region
let, y1 = asinwt ------1
y2 = ain(wt + theta)--------2
be the equation of two waves. We considered same amplitude, angular velocity but slightly different phase.
Here phase difference = theta
Now, the resultant wave can be given as
y = y1 + y2
= asinwt + asin(wt + theta)
=a(sinwt + sin(wt + theta))
y=(2acos(theta/2)*(sinwt+(theta/2))-------3
here, A = 2acos(theta/2)
We know intensity is directly proportional to A^2
therefor I directly porportional to A^2
I = A^2
I = 4a^2(cos(theta/2))
for maxima,
cos^2(theta/2) = 1
cos(theta/2)=+-1
cos(theta/2) = cos(n(pie)), n = 0,1,2....
or theta/2 = n(pie)
therefore theta = 2npie
here theta phase difference = lamda/2pie * theta phase difference = n*lamda
for minima cos^2(theta/2) = 0
or cos(theta/2) = 0
cos(theta/2) = cos(2n+1/2)pie
theta = (2n+1)pie
corresponding path difference
= lamda/2pie *(2n + 1)/2*pie
=(2n+1)/2 * lamda
maximum point 0, lamda,2lamda,3lamda
minimum points lamda/2 ,3/2lamda 5/2lamda
Young's double slit experiment
Let us consider a source of monochromatic light s. The light from s is passed through two slits s1 and s2. So that s1 and s2 behaves as two coherent source according to hygen's principal. let seperation between s1 adn s2 be d. COnsider a screen be place at distance D from two slits. Now when light from s1 and s2 reach the screen interference effect will result. COnsider a point p on the screen at distance y from center of screen. Now the path difference between lights from s1 and s2 at point P can be calculated which is S2N in fig.
Join C&P and suppose < PCO = theta
Let s1, s2 and N are very close to eath other, so S2N is approximately perpendicular to CP
Then,
sintheta = s2N/S1S2
s2N = dsintheta ---------1
Sp, point P will be bright fringe if
S2N = dsintheta = nlamda
or sintheta = nlamda/d ----------2
Now in triangle CPO, tantheta = PO/CO = y/D
Here in actual practice, theta is very small and for very small theta, sintheta = tantheta
y/D = nlamda/d
y = nlamdaD/d, n =0,1,2,3
for n = 0 n = 1 n = 2
y0 = 0 y1 = lamdaD/d y2 = 2lamdaD/d
Distance between two consecutive bright fringe = lamdaD/d
point p will be dark fringe if,
S2N = dsintheta = (2n+1)/2 * lamda
sintheta = (2n+1)/2 * lamda/d ----------4
From equation 3 and 4 for very small theta (sintheta = tantheta)
y/D = (2n+1)/2 * lamda/d
or y = (2n+1)/2 * lamda*D /d----------------5
Now, for
n=0 n=1
y0 = lamda*D/2d y1 = 3/2 lamdaD/d y2 = 5/2*lamdaD/d
fringe width = beta*D/d
Fringe width: The distance between two consequtive bright or dark fringe is called fringe width and denoted by beta
beta = lamda*D/d
to calculate lamda,
beta = lamda * D/d
lamda = beta*d/D
Join C&P and suppose < PCO = theta
Let s1, s2 and N are very close to eath other, so S2N is approximately perpendicular to CP
Then,
sintheta = s2N/S1S2
s2N = dsintheta ---------1
Sp, point P will be bright fringe if
S2N = dsintheta = nlamda
or sintheta = nlamda/d ----------2
Now in triangle CPO, tantheta = PO/CO = y/D
Here in actual practice, theta is very small and for very small theta, sintheta = tantheta
y/D = nlamda/d
y = nlamdaD/d, n =0,1,2,3
for n = 0 n = 1 n = 2
y0 = 0 y1 = lamdaD/d y2 = 2lamdaD/d
Distance between two consecutive bright fringe = lamdaD/d
point p will be dark fringe if,
S2N = dsintheta = (2n+1)/2 * lamda
sintheta = (2n+1)/2 * lamda/d ----------4
From equation 3 and 4 for very small theta (sintheta = tantheta)
y/D = (2n+1)/2 * lamda/d
or y = (2n+1)/2 * lamda*D /d----------------5
Now, for
n=0 n=1
y0 = lamda*D/2d y1 = 3/2 lamdaD/d y2 = 5/2*lamdaD/d
fringe width = beta*D/d
Fringe width: The distance between two consequtive bright or dark fringe is called fringe width and denoted by beta
beta = lamda*D/d
to calculate lamda,
beta = lamda * D/d
lamda = beta*d/D
Newton's ring
Let s be a source of monochromatic light. light from s are made parallel be a lense L which are then allowed to fall on a glass plate inclined at 45degree with horizontal part of light will be trasnmitted and some part will be reflected down. The reflected lights then allowed to fall on the plane surface of a plano convex lense place on a base plate with convex surface touching base plate. Now, some part of light will be reflected from the lower(convex) surface of plano-convex lens and some parts will be reflected from upper surface of base plate. During this process, there will be interference in reflected lights because there is a thin film of air introduced in between plano-convex lense and base plate. The fringes will be circular and called as Newton's ring.
Here interference is because of thin film of air So,
for bright fringr
2mew t cosr = (2n+1)/2 * lamda-------------1
n = 0,1,2
For dark fringe
2 mew t cos r = n*lamda -------------------2
n=0,1,2
Diagram
Let a ring be observed at height(thickness) OD = t at a distance r from the point of contact.
Now, from fig. we can have
AD*DB = ED*OD
r*r = (EO-OD)*OD
or r^2 = (2R - t)* t
As t is very small, we can have
r^2 = 2Ry
t = r^2/2R
Now, condition for bright fringe will be
2mew * r^2/2R * cosr = (2n+1)/2 * lamda
if r is very small, cosr = 1
or r^2 = 2n+1/2* R*lamda/mew
r =???? --------------4mew = 1
n= 0,1,2.....
For DArk fringe
2mew * r^2/2R = n*lamda
r=??????
n = 0,1,2......
Here interference is because of thin film of air So,
for bright fringr
2mew t cosr = (2n+1)/2 * lamda-------------1
n = 0,1,2
For dark fringe
2 mew t cos r = n*lamda -------------------2
n=0,1,2
Diagram
Let a ring be observed at height(thickness) OD = t at a distance r from the point of contact.
Now, from fig. we can have
AD*DB = ED*OD
r*r = (EO-OD)*OD
or r^2 = (2R - t)* t
As t is very small, we can have
r^2 = 2Ry
t = r^2/2R
Now, condition for bright fringe will be
2mew * r^2/2R * cosr = (2n+1)/2 * lamda
if r is very small, cosr = 1
or r^2 = 2n+1/2* R*lamda/mew
r =???? --------------4mew = 1
n= 0,1,2.....
For DArk fringe
2mew * r^2/2R = n*lamda
r=??????
n = 0,1,2......
Hygens Principal Geometrical Path
Wave front: Locus of thr particle having same phase of medium in which a wave travel is called wavefront and a perpendicular drawn to wavefront away from source is called ray of light
Hygen’s Principal: Hygens’s principle states that
1. every point on the primary wavefront behaves as the source of secondary wavefront in all possible direction
2. The direction of secondary wavefront is given by the forward envelop on the primary wavefront
Diagram of a circle with small circle in its circumference
Let us consider s be the source of light which emit light waves in all possible direction. At time t light will move distance ct and forms a primary wavefront of radius ct. The point like a,b,c,d.... on primary wavefront are now the source of secondary wavefront and emit light in all possible direction. Again in further time delta t the source like a,b,c,d... forms the wave front of radius c delta t. The locus touching all the tangent points in forward direction in wavefront of source a,b,c,d... is the direction of secondary wavefront
Geometrical and optical path
The path travelled by the light in air or vaccum is called the optical path and the path travelled by light in certain medium is called geometrical path
Diagram with a arrow passing through a rectangle called medium
Let us consider light travel a distance x in certain medium maving refractive index meu in time t then
Geometrical path x = vt
where v = velocity of light in medium
t = x/v
Now we can have the optical path in same time
optical path = ct = c*x/v = c/v*x = meu *x = refractive index * geometrical path
Hygen’s Principal: Hygens’s principle states that
1. every point on the primary wavefront behaves as the source of secondary wavefront in all possible direction
2. The direction of secondary wavefront is given by the forward envelop on the primary wavefront
Diagram of a circle with small circle in its circumference
Let us consider s be the source of light which emit light waves in all possible direction. At time t light will move distance ct and forms a primary wavefront of radius ct. The point like a,b,c,d.... on primary wavefront are now the source of secondary wavefront and emit light in all possible direction. Again in further time delta t the source like a,b,c,d... forms the wave front of radius c delta t. The locus touching all the tangent points in forward direction in wavefront of source a,b,c,d... is the direction of secondary wavefront
Geometrical and optical path
The path travelled by the light in air or vaccum is called the optical path and the path travelled by light in certain medium is called geometrical path
Diagram with a arrow passing through a rectangle called medium
Let us consider light travel a distance x in certain medium maving refractive index meu in time t then
Geometrical path x = vt
where v = velocity of light in medium
t = x/v
Now we can have the optical path in same time
optical path = ct = c*x/v = c/v*x = meu *x = refractive index * geometrical path
Diffraction
The bending of light from the corners of bostacle placed in path and spreading of light to the geometrical shadow is called comparable with the wavelength of light used then diffracted rays will overlay and results the diffraction fringe called as secondary minima and secondary maxima
Types od Diffraction
1) Freshel's diffraction: When diffraction is observed placing source or screen or both of them at a finite distance from slit. Then this is called as Fresnel's diffraction
2)Frauhafer diffraction
when source and screen are placed at infinte distance from slit and diffraction is observed then this types of diffraction is called fraunhofer diffraction. Lenses are used to observe this type of diffraction
Diffraction through Single slit
Let a parallel beam of light be incident on a slit of widtha then beam will be diffracted and we can observe a diffraction pattern on the screen, When slit width a is comparable with wavelength diffraction fringes can be observed.
Principal maxima: At the centre point of screen all the wave from slit will reach is same phase i.e path difference will be zero and hence intensity will be maximum or bright fringe occurs and called as principla maxima
Secondary minima
Let us consider lamda be the wavelength of the light used and a be the width of the slit. Now, divide the slit into two equal halves. Then taking waves travelling at an angle theta towards screen. Then path difference between 1st and 2nd wave will be
S2N = S1S1sintheta
= a/2 * sintheta
path difference = a/2 sin theta
If this path difference is ewusl to lamda/2 then dark fringe occurs.
i.e a*2 * sin theta = lamda/2
asin theta = lamda---------------1
Now if the slit is divided into four equal parts then path difference will be qual parts, then path difference will be equal to a/4 sin theta and dark fringe would occur if
a/4 * sin theta = lamda/2
a= sintheta = 2 lamda ------------2
and so on
asin theta = n lamda-----------------3
n = 1,2,3...................
FOr first secondary minima
asin theta = lamda
2nd secondary minima, asin theta = 2 lamda
Secondary maxima
When the slit is divide into three equal parts and two consecutive wave calcels effect6s of eath other and third remains unaffrected and gives bright fringe i.e
For first secondary maxima,
asin theta = 3/2 * lamda
2nd secondary maxima
asin theta = (2n+1)/2 * lamda
n= 1,2.........
Diffraction through double slit
Let us consider AB and CD be two identical slits having width a separated by an opaque BC of width b. Let a beam of monochromatic light be incident on the slits then interference and diffraction pattern can be observed on the screen.
Interference maxima and minima
At the centre of screen all the waves will meet in same phase so, this point will be of maximum intensity and called as principal maxima.
DIagram
Every point on the slit behaves as secondary wave source. Consider the central points of eath slits as source such that they will be coherent. If we take wave moving at anglr theta towards screen then path difference between these two S2N.
S2N = S1S2sintheta
=(a+b)sintheta
Now, interference maxima would occur if (a+b)sin theta = n lamda and interference minima would occur if
(a+b)sin theta = (2n+1)/2 * lamda
Diffraction maxima and minima
Let us consider two waves diffrented from upper edge of each slit moving at an angle theta towards screen. Then path difference between these two will be
S2N = S1S2 sin theta
=(a+b) sin theta
Diffraction maxima would occur if
(a+b) sin theta = n * lamda
and Diffraction minima would occur if
(a+b)sin theta = (2n+1)/2 * lamda
Diffraction grating
It is an arrangment of larger number of ruling ina glass plate of 1 inch in which the ruled lines behaves as opaque portion and glass left between each two line behaves as slit. Generally there are around 2000 lines in a glass plate of 1 inch.
If ruling is made on a transparent glass plate, the it is called a plain transmission grating and if it is made on a mirror then it is called as reflection grating. Here, combination of a single slit and a single opaque is called as grating element
If N be the no. of lines in a glass plate of one inch and a and b be the width of slit and opaque portion then
Na+Nb = 1 inch
(a+b) = 1/N inch = 2.54/N cm
Types od Diffraction
1) Freshel's diffraction: When diffraction is observed placing source or screen or both of them at a finite distance from slit. Then this is called as Fresnel's diffraction
2)Frauhafer diffraction
when source and screen are placed at infinte distance from slit and diffraction is observed then this types of diffraction is called fraunhofer diffraction. Lenses are used to observe this type of diffraction
Diffraction through Single slit
Let a parallel beam of light be incident on a slit of widtha then beam will be diffracted and we can observe a diffraction pattern on the screen, When slit width a is comparable with wavelength diffraction fringes can be observed.
Principal maxima: At the centre point of screen all the wave from slit will reach is same phase i.e path difference will be zero and hence intensity will be maximum or bright fringe occurs and called as principla maxima
Secondary minima
Let us consider lamda be the wavelength of the light used and a be the width of the slit. Now, divide the slit into two equal halves. Then taking waves travelling at an angle theta towards screen. Then path difference between 1st and 2nd wave will be
S2N = S1S1sintheta
= a/2 * sintheta
path difference = a/2 sin theta
If this path difference is ewusl to lamda/2 then dark fringe occurs.
i.e a*2 * sin theta = lamda/2
asin theta = lamda---------------1
Now if the slit is divided into four equal parts then path difference will be qual parts, then path difference will be equal to a/4 sin theta and dark fringe would occur if
a/4 * sin theta = lamda/2
a= sintheta = 2 lamda ------------2
and so on
asin theta = n lamda-----------------3
n = 1,2,3...................
FOr first secondary minima
asin theta = lamda
2nd secondary minima, asin theta = 2 lamda
Secondary maxima
When the slit is divide into three equal parts and two consecutive wave calcels effect6s of eath other and third remains unaffrected and gives bright fringe i.e
For first secondary maxima,
asin theta = 3/2 * lamda
2nd secondary maxima
asin theta = (2n+1)/2 * lamda
n= 1,2.........
Diffraction through double slit
Let us consider AB and CD be two identical slits having width a separated by an opaque BC of width b. Let a beam of monochromatic light be incident on the slits then interference and diffraction pattern can be observed on the screen.
Interference maxima and minima
At the centre of screen all the waves will meet in same phase so, this point will be of maximum intensity and called as principal maxima.
DIagram
Every point on the slit behaves as secondary wave source. Consider the central points of eath slits as source such that they will be coherent. If we take wave moving at anglr theta towards screen then path difference between these two S2N.
S2N = S1S2sintheta
=(a+b)sintheta
Now, interference maxima would occur if (a+b)sin theta = n lamda and interference minima would occur if
(a+b)sin theta = (2n+1)/2 * lamda
Diffraction maxima and minima
Let us consider two waves diffrented from upper edge of each slit moving at an angle theta towards screen. Then path difference between these two will be
S2N = S1S2 sin theta
=(a+b) sin theta
Diffraction maxima would occur if
(a+b) sin theta = n * lamda
and Diffraction minima would occur if
(a+b)sin theta = (2n+1)/2 * lamda
Diffraction grating
It is an arrangment of larger number of ruling ina glass plate of 1 inch in which the ruled lines behaves as opaque portion and glass left between each two line behaves as slit. Generally there are around 2000 lines in a glass plate of 1 inch.
If ruling is made on a transparent glass plate, the it is called a plain transmission grating and if it is made on a mirror then it is called as reflection grating. Here, combination of a single slit and a single opaque is called as grating element
If N be the no. of lines in a glass plate of one inch and a and b be the width of slit and opaque portion then
Na+Nb = 1 inch
(a+b) = 1/N inch = 2.54/N cm
Tuesday, May 25, 2010
Monochromatic Abberebation
Monochromatic aberration
1) Spherical aberration
The focal length of a lense for marginal and para-axial rays varies because of the thickness of lense. It os maximus for paraxial and minimum for marginal rays. This inability of lense to focus all rays toa single point is called spherical aberration fp-fm is measure of spherical aberration
Removal
a) If two lenses are kept at a distance equal to difference in their focal length spherical aberration will be minimized
b)If two(convex and concave) lense are kept in a suitable combination spherical aberration can be removed
c)By using Stops for marginal or for para-axial.
2)Comatic aberration
Spreading of image in the direction perpendicular to principal axis is called coma. The inability of a lense to focus all the incident light on a vertical plane from the object placed outside the axis is called comatic aberration
Removal
a) By using stop chromatic aberration can be minimized
b) By using lense which obeys Abbe's sine law
3)Astigmatism
The inability of a lense to focus all the incident rays in vertical and horizontal plane results spreading of image parallel to principal axis is called astigmatism
Removal
1) By using stops
4) Distortion
If a rectangular object be place infront of a lens, image will be formed either in barrel shaped or pin-cushioned shape. This defect is called distortion.
Removal
1) using stops
2) using suitable combination of two conver lense
Curvature of field
A lens has variable focal length for marginal and paraxial rays. Due to this image will be formed in a curved shape and called as curvature of field
1) Spherical aberration
The focal length of a lense for marginal and para-axial rays varies because of the thickness of lense. It os maximus for paraxial and minimum for marginal rays. This inability of lense to focus all rays toa single point is called spherical aberration fp-fm is measure of spherical aberration
Removal
a) If two lenses are kept at a distance equal to difference in their focal length spherical aberration will be minimized
b)If two(convex and concave) lense are kept in a suitable combination spherical aberration can be removed
c)By using Stops for marginal or for para-axial.
2)Comatic aberration
Spreading of image in the direction perpendicular to principal axis is called coma. The inability of a lense to focus all the incident light on a vertical plane from the object placed outside the axis is called comatic aberration
Removal
a) By using stop chromatic aberration can be minimized
b) By using lense which obeys Abbe's sine law
3)Astigmatism
The inability of a lense to focus all the incident rays in vertical and horizontal plane results spreading of image parallel to principal axis is called astigmatism
Removal
1) By using stops
4) Distortion
If a rectangular object be place infront of a lens, image will be formed either in barrel shaped or pin-cushioned shape. This defect is called distortion.
Removal
1) using stops
2) using suitable combination of two conver lense
Curvature of field
A lens has variable focal length for marginal and paraxial rays. Due to this image will be formed in a curved shape and called as curvature of field
Optical Fibre
Optical Fibre
It is a glass fibre of diameter around 125um of high refractive index in the core coated by a glass with low refractive index. Now a ray of light incident on one end will emerge out through other end suffering multiple total internal reflection without losing energy.
Types of optical fibre
1) Monomode: Optical fibre in which inner glass rod is thinner as compared to outer coating
2)Multimode: Optical fibre in which inner glass is thicker as compared to outer coating
on the basis of refractive index of glass used
1)Step index: Optical fibre which consist of glass rod of high refractive index of 1.52 in core and glass of refractive index 1.48 in coating
2)Graded Index: Optical fibre which have glass of high refractive index goes on decreasing gradually from core to surface.
Advantage of Graded index
In case of step index when a wave enters into the glass rod suffers disperson and so a wave will be total internally reflected from different point as shown in figure so that they will come out from other end in different time. But in case of graded index the wave after dispersion will be totslly internally reflected from diffrent height as shows in figure. When they suffer total internal reflection on lower side they will converge again in single point at different place so that single can be obtained at a single time from other end.
The minumum angle of incidence in air which makes total internal reflection possible in glass is called acceptance angle.
We have for total internal reflection
((meu))=1/(sinC)==>sinC=1/((meu))
This implies
sinC = ((meu1))/((meu2)) ------1
let us consider an incident ray be incidenting in glass making angle of incidence in air i such that ((meu1)) >((meu2)), total internal reflection r = 90 - 2
((meu2)) = sini/sinr = sini/sin(90-c) = sini/cosC
cosC = sinI/((meu2))--------------2
squaring and adding 1 and 2 will give i=sin(inverse)*sqrt((meu1)square - (men2)square)) This is the value of minimum angle of acceptance
Use of optical fibre
1 It is used to transfer electronic data or signal
2 It is used in telecommunication
3 It is used for direction signalling
4 It is used in medical purpose as optical pipe
5 It is used in computer networking
Advantage if optical fibre
1 It is fast and we can transfer signals without loss of much energy
2 It is cheap to be used for long distance
3 Repitors can be kept at about 35 km whereas they must be kept at about 1 km in other cables
4 It is most secured
5 It has very large bandwidth from 10^13 hz--10^16Hz
Disadvantage of optical fibre
1 It is expensive for short distance
2 Highly skilled manpower is needed for its maintenance
It is a glass fibre of diameter around 125um of high refractive index in the core coated by a glass with low refractive index. Now a ray of light incident on one end will emerge out through other end suffering multiple total internal reflection without losing energy.
Types of optical fibre
1) Monomode: Optical fibre in which inner glass rod is thinner as compared to outer coating
2)Multimode: Optical fibre in which inner glass is thicker as compared to outer coating
on the basis of refractive index of glass used
1)Step index: Optical fibre which consist of glass rod of high refractive index of 1.52 in core and glass of refractive index 1.48 in coating
2)Graded Index: Optical fibre which have glass of high refractive index goes on decreasing gradually from core to surface.
Advantage of Graded index
In case of step index when a wave enters into the glass rod suffers disperson and so a wave will be total internally reflected from different point as shown in figure so that they will come out from other end in different time. But in case of graded index the wave after dispersion will be totslly internally reflected from diffrent height as shows in figure. When they suffer total internal reflection on lower side they will converge again in single point at different place so that single can be obtained at a single time from other end.
The minumum angle of incidence in air which makes total internal reflection possible in glass is called acceptance angle.
We have for total internal reflection
((meu))=1/(sinC)==>sinC=1/((meu))
This implies
sinC = ((meu1))/((meu2)) ------1
let us consider an incident ray be incidenting in glass making angle of incidence in air i such that ((meu1)) >((meu2)), total internal reflection r = 90 - 2
((meu2)) = sini/sinr = sini/sin(90-c) = sini/cosC
cosC = sinI/((meu2))--------------2
squaring and adding 1 and 2 will give i=sin(inverse)*sqrt((meu1)square - (men2)square)) This is the value of minimum angle of acceptance
Use of optical fibre
1 It is used to transfer electronic data or signal
2 It is used in telecommunication
3 It is used for direction signalling
4 It is used in medical purpose as optical pipe
5 It is used in computer networking
Advantage if optical fibre
1 It is fast and we can transfer signals without loss of much energy
2 It is cheap to be used for long distance
3 Repitors can be kept at about 35 km whereas they must be kept at about 1 km in other cables
4 It is most secured
5 It has very large bandwidth from 10^13 hz--10^16Hz
Disadvantage of optical fibre
1 It is expensive for short distance
2 Highly skilled manpower is needed for its maintenance
Cardinal Points
Focal Points
If a parallel beam of light incident on a lens parallel to the principal axis then it will converge to a single point F2 on principal axix as shown in the figure. This point is known as focus or second focal point. Similarly a diverging beam from point F1 when incidented on lense then it will travel along a parallel direction to principal axis and the point is know as first focal point
Principal points
Let us consider a lense having principal focus f1 and f2. Consider a ray of light AB parallel to principal axis be incident on lens. Then it will refreact along BC and finally emerge out along CF2 i.e principal focus II. Now Producing AB in initial direction and CF2 in backward direction. Then they will intersect in one point H2. A plane passing through H2 and perpendicular to principal axis is called principal plane and point of intersection betweeb this principal point and principal axis is called 2nd principal point
Similarly if we consider a ray of light F1D from first principal plane be incidented on lens and refract along DE and emerge along EG parallel to principal axis. Then point of intersection H1 producing F1D and EG in backward direction. A plane passing forn H1 and perpendicular to principal axis is called first principal plane. The Point of intersection of first plane and principal axis is called as first principal point
Nodal Point
NOdal point are pair of Conjugate points having unit angular magnification. This ,eans when an incident ray be incident on lense directed to either of nodal points and parallel to initial direction
By definition, Q1=Q2
So that P1N1=P2N2
H1H2=N1N2
If a parallel beam of light incident on a lens parallel to the principal axis then it will converge to a single point F2 on principal axix as shown in the figure. This point is known as focus or second focal point. Similarly a diverging beam from point F1 when incidented on lense then it will travel along a parallel direction to principal axis and the point is know as first focal point
Principal points
Let us consider a lense having principal focus f1 and f2. Consider a ray of light AB parallel to principal axis be incident on lens. Then it will refreact along BC and finally emerge out along CF2 i.e principal focus II. Now Producing AB in initial direction and CF2 in backward direction. Then they will intersect in one point H2. A plane passing through H2 and perpendicular to principal axis is called principal plane and point of intersection betweeb this principal point and principal axis is called 2nd principal point
Similarly if we consider a ray of light F1D from first principal plane be incidented on lens and refract along DE and emerge along EG parallel to principal axis. Then point of intersection H1 producing F1D and EG in backward direction. A plane passing forn H1 and perpendicular to principal axis is called first principal plane. The Point of intersection of first plane and principal axis is called as first principal point
Nodal Point
NOdal point are pair of Conjugate points having unit angular magnification. This ,eans when an incident ray be incident on lense directed to either of nodal points and parallel to initial direction
By definition, Q1=Q2
So that P1N1=P2N2
H1H2=N1N2
Codition for achromatism
Combination of two or more lenses such that there will not be a chromatic aberration is known as achromatic lense and the condition is called as achromatism
Mathmatically, df = fr-fv = 0
Now let us take two lenses having focal length f1&f2 and are separated by a distance x. Then theequivalent focal length of combination will be
1/f=1/f1 + 1/f2 - x/(f1*f2)
Diffrentiating this equation we have
-df/f2 + -df1/f1^2 - df2/f2^2 - x(-df1/f1^2f2 - df2/f1f2^2)
But we have
-df1/f1=w1 and -df2/f2 = w2
where w1 and w2 are the dispersive power of 1st and 2nd ;ems
-df/f2 = w1/f1 + w2/f2 - x( w1/f1f2 + w2/f1/f2)
For achromatism df = 0
w1/f1 + w2/f2 = x(w1/f1f2 + w2/f1f2) = 0
When two lense are kept in contact then x = 0
w1/f1 + w2/f2 = 0
f1/f2 = -w1/w2
The negative sign here indicates combination of lense must be of one convex and another concave
Mathmatically, df = fr-fv = 0
Now let us take two lenses having focal length f1&f2 and are separated by a distance x. Then theequivalent focal length of combination will be
1/f=1/f1 + 1/f2 - x/(f1*f2)
Diffrentiating this equation we have
-df/f2 + -df1/f1^2 - df2/f2^2 - x(-df1/f1^2f2 - df2/f1f2^2)
But we have
-df1/f1=w1 and -df2/f2 = w2
where w1 and w2 are the dispersive power of 1st and 2nd ;ems
-df/f2 = w1/f1 + w2/f2 - x( w1/f1f2 + w2/f1/f2)
For achromatism df = 0
w1/f1 + w2/f2 = x(w1/f1f2 + w2/f1f2) = 0
When two lense are kept in contact then x = 0
w1/f1 + w2/f2 = 0
f1/f2 = -w1/w2
The negative sign here indicates combination of lense must be of one convex and another concave
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