(Concept, fundamentals, logic, computer, research)

Dedicated to “Ma Saraswati”


This book is written for the 1st year students of computer application for MLSU. In this book IT subject is intended for anyone interested in knowing about computers. IT subject also useful for CA students for their ITSM subject. “THE KEY OF SUCCESS” specially wrote for BCA 1st year students. More specifically, different classes of readers can benefit from this book-
It can be used as a textbook for the first course in computers taught in diploma and bachelor’s programming in computer science, computer application, and information technology.

It can be used as a textbook for the first course in computer taught to B. Sc. (IT) and B. Com. Students.

There are four subjects in this book that is Information Technology, Problem Solving through C, Computer Organization and Physics.

It is hoped that students will find the book very helpful.
Although every care has been taken to avoid mistakes and misprint, yet it is very difficult to claim perfection.

Special Thanks to “Pratik Badala [PK]"

Website (Block) :-


      UNIT - 1

Basic Concepts : 

Definition of Science- 

Science (from Latin scientia, meaning "knowledge") is a systematic enterprise that builds and organizes knowledge in the form of testable explanations and predictions about the universe.[1] In an older and closely related meaning (found, for example, in Aristotle), "science" refers to the body of reliable knowledge itself, of the type that can be logically and rationally explained (see History and philosophy below). Since classical antiquity science as a type of knowledge was closely linked to philosophy. In the early modern era the words "science" and "philosophy" were sometimes used interchangeably in the English language.[citation needed] By the 17th century, natural philosophy (which is today called "natural science") was considered a separate branch of philosophy.[3] However, "science" continued to be used in a broad sense denoting reliable knowledge about a topic, in the same way it is still used in modern terms such as library science or political science.
In modern use, "science" more often refers to a way of pursuing knowledge, not only the knowledge itself. It is "often treated as synonymous with 'natural and physical science', and thus restricted to those branches of study that relate to the phenomena of the material universe and their laws, sometimes with implied exclusion of pure mathematics. This is now the dominant sense in ordinary use."[4] This narrower sense of "science" developed as scientists such as Johannes Kepler, Galileo Galilei and Isaac Newton began formulating laws of nature such as Newton's laws of motion. In this period it became more common to refer to natural philosophy as "natural science". Over the course of the 19th century, the word "science" became increasingly associated with the scientific method, a disciplined way to study the natural world, including physics, chemistry, geology and biology. It is in the 19th century also that the term scientist was created by the naturalist-theologian William Whewell to distinguish those who sought knowledge on nature from those who sought knowledge on other disciplines. The Oxford English Dictionary dates the origin of the word "scientist" to 1834. This sometimes left the study of human thought and society in a linguistic limbo, which was resolved by classifying these areas of academic study as social science. Similarly, several other major areas of disciplined study and knowledge exist today under the general rubric of "science", such as formal science and applied science.

engineering and technology- Engineering & Technology (E&T) is a science, engineering and technology magazine published by the Institution of Engineering and Technology (IET) in the United Kingdom. The magazine is issued 12 times per year, and is distributed to the 150,000 plus membership of the IET.
The magazine was launched in April 2008 as a result of the merger between the Institution of Electrical Engineers and the Institution of Incorporated Engineers on 31 March 2006. Prior to the merger, both organisations had their own membership magazine, the IEE's monthly IEE Review and the IIE's Engineering Technology.[1] Engineering & Technology is an amalgamation of the two, and was initially published twelve times per year. Alongside this, members also received one of seven other monthly magazines published by the IET relating to a field of the subject of their choice, with the option to purchase any of the other titles. In January 2008, the IET merged these seven titles into E&T to make a nearly fortnightly magazine with a larger pagination, providing all members with one magazine covering all topics. In January 2011 the frequency was reduced to 12 times per year.
The Editor-in-Chief for E&T and the IET's other magazines that include the teenagers' magazine Flipside, is Dickon Ross.

Importance of Mathematics and Physics in ICT-  The School of Computer Science, Physics and Mathematics at Linnaeus University has taken the initiative for a new regional competence centre, aiming to stimulate the interest and education in mathematics, physics, technology and ICT (information and communication technology) among teachers and students. The objective is to establish a modern and successful science centre at Linnaeus University within the next few years.
Recent reports about decreasing knowledge among Swedish pupils in subjects such as mathematics, natural sciences and technology paint a dark picture. This is an alarming development, not least for the many Swedish businesses and organizations which depend upon a future work force with a sound knowledge of mathematics, physics, technology and ICT. New initiatives are required to ensure that the innovative force prevalent in research and business also benefits primary and secondary schools.
The School of Computer Science, Physics and Mathematics at Linnaeus University aims to contribute to a more positive development in this area by starting a competence centre. The objective is to create a place where teachers and pupils from regional schools can meet university staff, businesses and other organizations to share experiences, hold courses and stimulate skills development. The centre will look at the integration of mathematics and physics education, ICT and learning, with special focus on school activities and teacher education. If carried out in full, this establishment will be the only one of its kind in Sweden.
The initiative is based on the results from a range of national and international projects which researchers from the School of Computer Science, Physics and Mathematics have been involved in during the past years. The collaboration with schools in the region has already come a long way. For example, teachers and researchers from media technology and mathematics education have – together with local teachers – developed new concepts to support the education and learning of mathematics, physics and other subjects where mobile technology and social media are important factors.
The competence centre is financed by the School of Computer Science, Physics and Mathematics, with part-funding from the Regional Council of Southern Småland and external assignments.
– The collaboration between the university's competence centre and the Regional Council of Southern Småland will be crucial for our endeavours to increase the quality in Kronoberg's municipalities, according to Åke Sjöberg, CEO for AV-Media Kronoberg. AV-Media Kronoberg plays a significant role as a centre for skills development and technology support for ICT in Kronoberg county's schools.
– We see the establishment of this competence centre as a strategic contribution and part of the subject-didactic development with ICT support which already takes place at our department – not least in relation to the regional demand for skills development, says Associate Professor Staffan Carius, head of the School of Computer Science, Physics and Mathematics.
Our long-term intention for the competence centre is that we eventually could establish a science centre at Linnaeus University, which will be serve as an example for how schools, businesses, organizations and the university together can increase the interest in mathematics, physics, technology and ICT.

Units and Dimension- A dimension is a property that can be measured such as distance, time, temperature, speed.
A unit is a basic division of a measured quantity and it enables to say how much of the quantity we have - 10 miles, 2 hours etc.
Base units and derived units
Base units are units that are defined by reference to some external standard. This external standard is arbitrary but is a matter of common agreement.
Derived units are units that are defined by reference to combinations of the base units.
The SI system of units.
The SI system is an internationally agreed system of units based on seven base units. These are listed in table 1 below. Some of the more important derived units are listed in table 

Base units of the SI system of units

Quantity      Unit Symbol 
Mass          kilogramme   kg 
Length            metre   m 
Time           second   s 
Mole             mole   mol 
Temperatur         kelvin    K 
Electric current   ampere A 
Light intensity    candela cd 

  Some derived units in the SI system
Quantity Unit Symbol 
Volume cubic   metre m3 
Force Newton = kg m s-2 N 
Pressure Pascal = N m-2 Pa 
Work, Energy Joule = N m J 
Power Watt = J s-1 W 
Molar concentration Molar = mol dm-3 or mol L-1 M 
Multiples of the basic units are used to avoid having to write very large or very small numbers. These are listed in table 3.
MKSA Units- The MKS system of units is a physical system of units that expresses any given measurement using fundamental units of the metre, kilogram, and/or second (MKS).
Historically the MKS system of units succeeded the cgs system of units and laid the blueprint for the International System of Units, which now serves as the international standard. Therefore the exact composition of the MKS system is a historical issue. As a matter of historical record the MKS system incorporated fundamental units other than the metre, kilogram, and second in addition to derived units. An incomplete list of the fundamental and derived units appears below. Since the MKS system of units never had a governing body to rule on a standard definition, the list of units depended on different conventions at different times.
• Cycle. (This dimensionless quantity became synonymous with the term "cycle per second" as an abbreviation. This circumstance confused the exact definition of the term cycle. Therefore the phrase "cycle per metre" became ill-defined. The cycle did not become an SI unit.)
• Cycle per second.[1]
• Cycle per metre. (This measure of wavenumber became ill-defined due to the abbreviation of "cycle per second" as "cycle".)

time and length with examples-  Length time bias is a form of selection bias, a statistical distortion of results which can lead to incorrect conclusions about the data. Length time bias can occur when the lengths of intervals are analysed by selecting intervals that occupy randomly chosen points in time or space. This process favors longer intervals, thus skewing the data.
Length time bias is often discussed in the context of the benefits of cancer screening, where it can lead to the perception that screening leads to better outcomes when in reality it has no effect. Fast-growing tumors generally have a shorter asymptomatic phase than slower-growing tumors. This means that there is a shorter period of time when the cancer is present in the body (and therefore might be detected by screening) but not yet large enough to cause symptoms, which would cause the patient to seek medical care and be diagnosed without screening. As a result, if the same number of slow-growing and fast-growing tumors appear in a year, the screening test will detect more slow-growers than fast-growers. If these slow growing tumors are less likely to be fatal than the fast growers are, the people whose cancer is detected by screening will do better, on average, than the people whose tumors are detected from symptoms (or at autopsy), even if there is no real benefit to catching the cancer earlier. This can give the impression that detecting cancers through screening causes cancers to be less dangerous, when the reality is that less dangerous cancers are simply more likely to be detected by screening. 

Measurement of length using vernier caliper and screw gauge:

vernier caliper-
Instructions on use
• The Vernier caliper is an extremely precise measuring instrument; the reading error is 1/20 mm = 0.05 mm. 
• Close the jaws lightly on the object to be measured. 
• If you are measuring something with a round cross section, make sure that the axis of the object is perpendicular to the caliper. This is necessary to ensure that you are measuring the full diameter and not merely a chord. 
• Ignore the top scale, which is calibrated in inches. 
• Use the bottom scale, which is in metric units. 
• Notice that there is a fixed scale and a sliding scale. 
• The boldface numbers on the fixed scale are centimeters. 
• The tick marks on the fixed scale between the boldface numbers are millimeters. 
• There are ten tick marks on the sliding scale. The left-most tick mark on the sliding scale will let you read from the fixed scale the number of whole millimeters that the jaws are opened. 

• In the example above, the leftmost tick mark on the sliding scale is between 21 mm and 22 mm, so the number of whole millimeters is 21. 
• Next we find the tenths of millimeters. Notice that the ten tick marks on the sliding scale are the same width as nine ticks marks on the fixed scale. This means that at most one of the tick marks on the sliding scale will align with a tick mark on the fixed scale; the others will miss. 
• The number of the aligned tick mark on the sliding scale tells you the number of tenths of millimeters. In the example above, the 3rd tick mark on the sliding scale is in coincidence with the one above it, so the caliper reading is (21.30 ± 0.05) mm. 
• If two adjacent tick marks on the sliding scale look equally aligned with their counterparts on the fixed scale, then the reading is half way between the two marks. In the example above, if the 3rd and 4th tick marks on the sliding scale looked to be equally aligned, then the reading would be (21.35 ± 0.05) mm. 
• On those rare occasions when the reading just happens to be a "nice" number like 2 cm, don't forget to include the zero decimal places showing the precision of the measurement and the reading error. So not 2 cm, but rather (2.000 ± 0.005) cm or (20.00 ± 0.05) mm. 
Screw gauge- 
Description : Screw Gauge consists of  U shaped metallic frame.To one side of this U frame a long hallow cylindrical tube with a nut inside it, the inner side of cylindrical nut contains a uniform thread cut in it.On the other side of U frame a fixed stud  with a plane face is attached.
A screw  is fitted in the cylindrical nut.One side of the screw  has a plane face similar to that of stud  . The faces of  and  are plane and parallel to one another. The other end of the screw  carries a milled head ‘H’ attached to a cap ‘C’ with a sloping edge. When the head H is rotated, the screw moves ”to and fro” in the nut.The milled head H is provided with a safety device ‘D’ to rotate the head H.When the object is held between the stud  and  screw    and the head H is rotated using the safety device (D), it produces crackling sound when optimum pressure is applied on the object.
The screw gauge works on the principle of screw.
The outer surface of long cylindrical nut consists of a thick horizontal line ‘P’ parallel to the axis of cylindrical tube.This line ‘P’ is called Index line. Along the index line a scale is graduated in millimeters.This scale is called Pitch Scale.On the sloping edge of the cap ‘C’ a circular scale is graduated, which consists of 100 equal divisions, this scale is called Head scale.

scalar and vector product of two vector-

Vectors can be multiplied in two different ways: the scalar and vector product. As the name says, a scalar product of two vectors results in a scalar quantity, and a vector product in a vector quantity.
1. Scalar Product (=> applet)
The result of this product is a scalar quantity. The scalar product between two vector is denoted by a thick dot: 
 •  = | | | | cosqab
Please note:  •  =  •  .
If  is perpendicular to  , the scalar product vanishes. 
2. Vector Product (=> applet)
The result of this product is a vector quantity. The vector product between two vector is denoted by a cross (the product is sometimes also called "cross-product"): 
 x  =  
Please note:  x  = -  x  
The vector  is perpendicular to the plane of  and  , and its magnitude is given by: | | = | | |  | sin AB 

The direction of  is given by the right hand rule: put the thumb of your right hand along  , and the index finger along  , then point your middle finger perpendicular to thumb and index finger - this is the direction of  . If  is parallel to  , the vector product vanishes.

Optical instruments

Electromagnetic spectrum- 
A diagram of the electromagnetic spectrum, showing various properties across the range of frequencies and wavelengths
The electromagnetic spectrum is the range of all possible frequencies of electromagnetic radiation.[1] The "electromagnetic spectrum" of an object has a different meaning, and is instead the characteristic distribution of electromagnetic radiation emitted or absorbed by that particular object.
The electromagnetic spectrum extends from below the low frequencies used for modern radio communication to gamma radiation at the short-wavelength (high-frequency) end, thereby covering wavelengths from thousands of kilometers down to a fraction of the size of an atom. The limit for long wavelengths is the size of the universe itself, while it is thought that the short wavelength limit is in the vicinity of the Planck length,[2] although in principle the spectrum is infinite and continuous.
Most parts of the electromagnetic spectrum are used in science for spectroscopic and other probing interactions, as ways to study and characterize matter.[3] In addition, radiation from various parts of the spectrum has found many other uses for communications and manufacturing (see electromagnetic radiation for more applications).

Frequency- The number of cycles per unit of time is called the frequency. For convenience, frequency is most often measured in cycles per second (cps) or the interchangeable Hertz (Hz) (60 cps = 60 Hz), named after the 19th C. physicist. 1000 Hz is often referred to as 1 kHz (kilohertz) or simply '1k' in studio parlance.

The range of human hearing in the young is approximately 20 Hz to 20 kHz—the higher number tends to decrease with age (as do many other things). It may be quite normal for a 60-year-old to hear a maximum of 16,000 Hz. 

wavelength and energy-
Wavelength of a sine wave, ?, can be measured between any two points with the same phase, such as between crests, or troughs, or corresponding zero crossings as shown.
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.[1] It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a characteristic of both traveling waves and standing waves, as well as other spatial wave patterns. Wavelength is commonly designated by the Greek letter lambda (?). The concept can also be applied to periodic waves of non-sinusoidal shape. The term wavelength is also sometimes applied to modulated waves, and to the sinusoidal envelopes of modulated waves or waves formed by interference of several sinusoids.[  The SI unit of wavelength is the meter.
Assuming a sinusoidal wave moving at a fixed wave speed, wavelength is inversely proportional to frequency: waves with higher frequencies have shorter wavelengths, and lower frequencies have longer wavelengths.[ 
Examples of wave-like phenomena are sound waves, light, and water waves. A sound wave is a variation in air pressure, while in light and other electromagnetic radiation the strength of the electric and the magnetic field vary. Water waves are variations in the height of a body of water. In a crystal lattice vibration, atomic positions vary.
Wavelength is a measure of the distance between repetitions of a shape feature such as peaks, valleys, or zero-crossings, not a measure of how far any given particle moves. For example, in sinusoidal waves over deep water a particle in the water moves in a circle of the same diameter as the wave height, unrelated to wavelength. 

associated with electromagnetic radiation-
The electromagnetic waves that compose electromagnetic radiation can be imagined as a self-propagating transverse oscillating wave of electric and magnetic fields. This diagram shows a plane linearly polarized EMR wave propagating from left to right. The electric field is in a vertical plane and the magnetic field in a horizontal plane. The two types of fields in EMR waves are always in phase with each other, and no matter how powerful, have a ratio of electric to magnetic intensity which is fixed and never varies
Electromagnetic radiation (EM radiation or EMR) is a form of energy emitted and absorbed by charged particles which exhibits wave-like behavior as it travels through space. EMR has both electric and magnetic field components, which stand in a fixed ratio of intensity to each other, and which oscillate in phase perpendicular to each other and perpendicular to the direction of energy and wave propagation. In a vacuum, electromagnetic radiation propagates at a characteristic speed, the speed of light.
Electromagnetic radiation is a particular form of the more general electromagnetic field (EM field), which is produced by moving charges. Electromagnetic radiation is associated with EM fields that are far enough away from the moving charges that produced them that absorption of the EM radiation no longer affects the behavior of these moving charges. These two types or behaviors of EM field are sometimes referred to as the near and far field. In this language, EMR is merely another name for the far-field. Charges and currents directly produce the near-field. However, charges and currents produce EMR only indirectly—rather, in EMR, both the magnetic and electric fields are associated with changes in the other type of field, not directly by charges and currents. This close relationship assures that the electric and magnetic fields in EMR exist in a constant ratio of strengths to each other, and also to be found in phase, with maxima and nodes in each found at the same places in space.
EMR carries energy—sometimes called radiant energy—through space continuously away from the source (this is not true of the near-field part of the EM field). EMR also carries both momentum and angular momentum. These properties may all be imparted to matter with which it interacts. EMR is produced from other types of energy when created, and it is converted to other types of energy when it is destroyed. The photon is the quantum of the electromagnetic interaction, and is the basic "unit" or constituent of all forms of EMR. The quantum nature of light becomes more apparent at high frequencies (or high photon energy). Such photons behave more like particles than lower-frequency photons do.
In classical physics, EMR is considered to be produced when charged particles are accelerated by forces acting on them. Electrons are responsible for emission of most EMR because they have low mass, and therefore are easily accelerated by a variety of mechanisms. Rapidly moving electrons are most sharply accelerated when they encounter a region of force, so they are responsible for producing much of the highest frequency electromagnetic radiation observed in nature. Quantum processes can also produce EMR, such as when atomic nuclei undergo gamma decay, and processes such as neutral pion decay.
EMR is classified according to the frequency of its wave. The electromagnetic spectrum, in order of increasing frequency and decreasing wavelength, consists of radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays. The eyes of various organisms sense a small and somewhat variable but relatively small range of frequencies of EMR called the visible spectrum or light.

formation of image by lens-
There are two alternative methods of locating the image formed by a thin lens. Just as for spherical mirrors, the first method is graphical, and the second analytical. 
The graphical method of locating the image formed by a thin lens involves drawing light-rays emanating from key points on the object, and finding where these rays are brought to a focus by the lens. This task can be accomplished using a small number of simple rules. 
Consider a converging lens. It is helpful to define two focal points for such a lens. The first, the so-called image focus, denoted  , is defined as the point behind the lens to which all incident light-rays parallel to the optic axis converge after passing through the lens. This is the same as the focal point  defined previously. The second, the so-called object focus, denoted  , is defined as the position in front of the lens for which rays emitted from a point source of light placed at that position would be refracted parallel to the optic axis after passing through the lens. It is easily demonstrated that the object focus  is as far in front of the optic centre  of the lens as the image focus  is behind  . The distance from the optic centre to either focus is, of course, equal to the focal length  of the lens. The image produced by a converging lens can be located using just three simple rules: 
• An incident ray which is parallel to the optic axis is refracted through the image focus  of the lens. 
• An incident ray which passes through the object focus  of the lens is refracted parallel to the optic axis. 
• An incident ray which passes through the optic centre  of the lens is not refracted at all. 
The last rule is only an approximation. It turns out that although a light-ray which passes through the optic centre of the lens does not change direction, it is displaced slightly to one side. However, this displacement is negligible for a thin lens. 
Figure 80 illustrates how the image  of an object  placed in front of a converging lens is located using the above rules. In fact, the three rays, 1-3, emanating from the tip  of the object, are constructed using rules 1-3, respectively. Note that the image is real (since light-rays actually cross), inverted, and diminished. 
Image formation by a converging lens.
Consider a diverging lens. It is again helpful to define two focal points for such a lens. The image focus  is defined as the point in front of the lens from which all incident light-rays parallel to the optic axis appear to diverge after passing through the lens. This is the same as the focal point  defined earlier. The object focus  is defined as the point behind the lens to which all incident light-rays which are refracted parallel to the optic axis after passing through the lens appear to converge. Both foci are located a distance  from the optic centre, where  is the focal length of the lens. The image produced by a diverging lens can be located using the following three rules: 
• An incident ray which is parallel to the optic axis is refracted as if it came from the image focus  of the lens. 
• An incident ray which is directed towards the object focus  of the lens is refracted parallel to the optic axis. 
• An incident ray which passes through the optic centre  of the lens is not refracted at all. 
Figure 81 illustrates how the image  of an object  placed in front of a diverging lens is located using the above rules. In fact, the three rays, 1-3, emanating from the tip  of the object, are constructed using rules 1-3, respectively. Note that the image is virtual (since light-rays do not actually cross), upright, and diminished. 
Image formation by a diverging lens.
Let us now investigate the analytical method. Consider an object of height  placed a distance  in front of a converging lens. Suppose that a real image of height  is formed a distance  behind the lens. As is illustrated in Fig. 82, the image can be located using rules 1 and 3, discussed above. 
Image formation by a converging lens.

Now, the right-angled triangles  and  are similar, so 
Here, we have adopted the convention that the image height  is negative if the image is inverted. The magnification of a thin converging lens is given by 

This is the same as the expression (352) for the magnification of a spherical mirror. Note that we are again adopting the convention that the magnification is negative if the image is inverted. 
The right-angled triangles  and  are also similar, and so 
The above expression can be rearranged to give 
Note that this is exactly the same as the formula (358) relating the image and object distances in a spherical mirror. 
Although formulae and were derived for the case of a real image formed by a converging lens, they also apply to virtual images, and to images formed by diverging lenses, provided that the following sign conventions are adopted. First of all, as we have already mentioned, the focal length  of a converging lens is positive, and the focal length of a diverging lens is negative. Secondly, the image distance  is positive if the image is real, and, therefore, located behind the lens, and negative if the image is virtual, and, therefore, located in front of the lens. It immediately follows, from Eq. (364), that real images are always inverted, and virtual images are always upright. 
Table 7 shows how the location and character of the image formed by a converging lens depend on the location of the object. Here, the point  is located on the optic axis two focal lengths in front of the optic centre, and the point  is located on the optic axis two focal lengths behind the optic centre. Note the almost exact analogy between the image forming properties of a converging lens and those of a concave spherical mirror. 
Rules for image formation by converging lenses.
Position of object Position of image Character of image
At                          At                    Real, zero size
Between  and              Between  and          Real, inverted, diminished
At                          At                   Real, inverted, same size
Between  and             Between  and            Real, inverted, magnified
At                          At                  Virtual, upright, magnified
At                          At                  Virtual, upright, same size

shows how the location and character of the image formed by a diverging lens depend on the location of the object. Note the almost exact analogy between the image forming properties of a diverging lens and those of a convex spherical mirror. 

Position of object Position of image Character of image
At                            At                  Virtual, zero size
Between  and            Between  and         Virtual, upright, diminished
At                            At              Virtual, upright, same size

Finally, let us reiterate the sign conventions used to determine the positions and characters of the images formed by thin lenses: 
• The height  of the image is positive if the image is upright, with respect to the object, and negative if the image is inverted. 
• The magnification  of the image is positive if the image is upright, with respect to the object, and negative if the image is inverted. 
• The image distance  is positive if the image is real, and, therefore, located behind the lens, and negative if the image is virtual, and, therefore, located in front of the lens. 
• The focal length  of the lens is positive if the lens is converging, so that the image focus  is located behind the lens, and negative if the lens is diverging, so that the image focus  is located in front of the lens. 

Eye- A lens is a transparent material, such a glass, that has either one curved surface and one flat surface or two curved surfaces. As with mirrors, these two lenses are either convex or concave. Convex lenses are thicker in the middle then the edges and concave are thicker at the edges then the middle. When light travels through lenses, refraction occurs. The light bends either outward or inward, it depends on the lens. 
 The lens of your eye is a double convex lens. Its job is to focus the image on the retina of the eye. If one is farsighted, the lens in the eye causes the focus to be behind the retina. These people see far but have some difficultly seeing close-up. The lens focuses behind the retina because the actual eyeball is too short from front to back. To correct this farsightedness, the person would wear glasses or contacts with convex lenses. What would be the result and treatment if a person's eyeball was too long from front to back? 
its retina to detect the image whereas the camera uses film to detect the image.
Your eye and a camera are quite similar. Both use convex lenses to focus the image upside-down. Your eye uses 
if one is nearsighted, the lens in the eye
causes the focus to be behind the retina. These people see close-up but have some difficultly seeing far away. The lens focuses infront of the retina because the actual eyeball is too long from front to back. To correct this nearsightedness, the person would wear glasses or contacts with concave lenses. Take a look at the two diagrams.

Sensitivity of eye to electromagnetic radiation-
What do light, X-rays, heat radiation, microwaves, radio waves, and gamma radiation
have in common? Despite their differences, they are all the same kind of “stuff.” They all
travel through space and have similar electrical and magnetic effects on matter. This “stuff”
is called electromagnetic radiation, because it travels (radiates) and has electrical and
magnetic effects.
Electromagnetic radiation is the means for many of our interactions with the world: light
allows us to see; radio waves give us TV and radio; microwaves are used in radar communications;
X-rays allow glimpses of our internal organs; and gamma rays let us eavesdrop
on exploding stars thousands of light-years away. Electromagnetic radiation is the messenger,
or the signal from sender to receiver. The sender could be a TV station, a star, or the
burner on a stove. The receiver could be a TV set, an eye, or an X-ray film. In each case, the
sender gives off or reflects some kind of electromagnetic radiation.
All these different kinds of electromagnetic radiation actually differ only in a single
property — their wavelength. When electromagnetic radiation is spread out according to its
wavelength, the result is a spectrum, as seen in Fig. 1. The visible spectrum, as seen in a
rainbow, is only a small part of the whole electromagnetic spectrum. The electromagnetic
spectrum is divided into five major types of radiation. As shown in Fig. 1, these include
radio waves (including microwaves), light (including ultraviolet, visible, and infrared), heat
radiation, X-rays, gamma rays, and cosmic rays. Your eye can detect only part of the light

defects of vision- There are four types of defect of the Eye: Myopia, Hypermetropia,Presbyopia and Astigmatism.  Below are given the nature of the defect, its causes and corrective measures:-
Nearsightedness, also called myopia is common name for impaired vision in which a person sees near objects clearly while distant objects appear blurred.  In such a defective eye, the image of a distant object is formed in front of the retina and not at the retina itself. Consequently, a nearsighted person cannot focus clearly on an object farther away than the far point for the defective eye.
This defect arises because the power of the eye is too great due to the decrease in focal length of the crystalline lens. This may arise due to either
(i)                   excessive curvature of the cornea, or
(ii)                  elongation of the eyeball.
Correction :-
This defect can be corrected by using a concave (diverging) lens. A concave lens of appropriate power or focal length is able to bring the image of the object back on the retina itself.
Method for calculating the power of the corrective lens: -
For calculating the required power of a corrective lens, we first find the power of the eye at its far point. Then, we select a corrective lens of appropriate power to move the far point to infinity. We then use the thin lens formula , written in terms of power P of the lens as
The image distance v of the eye can be taken as 0.02 m approximately.
Farsightedness, also called hypermetropia, common name for a defect in vision in which a person sees near objects with blurred vision, while distant objects appear in sharp focus. In this case, the image is formed behind the retina.
This defect arises because either
(i)                   the focal length of the eyelens is too great, or
(ii)                  the eyeball becomes too short, so that light rays from the nearby object, say at point N, cannot be brought to focus on the retina to give a distinct image.
This defect can be corrected by using a convex (converging) lens of appropriate focal length. When the object is at N’, the eye exerts its maximum power of accommodation. Eyeglasses with converging lenses supply the additional focussing power required for forming the image on the retina.
Presbyopia, progressive form of farsightedness that affects most people by their early 60s.   The power of accommodation of the eye decreases with ageing. Most people find that the near point gradually recedes.
Cause and cure:
It arises due to the gradual weakening of the ciliary muscles and diminishing flexibility of the crystalline lens. Simple reading eyeglasses with convex lenses correct most cases of presbyopia. Sometimes, a person may suffer from both myopia and hypermetropia. Such people often require bi-focal lenses. In the bi-focal lens, the upper portion of the bi-focal lens is a concave lens, used for distant vision. The lower part of the bi-focal lens is a convex lens, used for reading purposes.
Astigmatism, a defect in the outer curvature on the surface of the eye that causes distorted vision.In astigmatism, a person cannot simultaneously focus on both horizontal and vertical lines.
This defect is usually due to the cornea that is not perfectly spherical. Consequently, it has different curvatures in different directions in vertical and horizontal planes. This results in objects in one direction being well-focussed, while those in a perpendicular direction not wellfocussed.
This defect can be corrected by using eyeglasses with cylindrical lenses oriented to compensate for the irregularities in the cornea.

Brief understanding of telescope- The telescope continued to improve over the years and remained one of the primary tools for astronomy. In the 17th century, Sir Isaac Newton improved on the design of the reflector to create the telescope which bears his name. During the 20th century, German astronomer Bernhard Schmidt placed his mark on the design of the catadioptric telescope as did Russian astronomer, and D. Maksutov and Dutch astronomer, A. Bouwers. 

Telescopes come in three basic designs; Refractor, Reflector, and Catadioptric. A refractor uses two lenses, one to collect light and focus it as a sharp image, while the other magnifies the image for the viewer. A reflector gathers the light at the bottom of the scope by a concave mirror, called the Primary while the image is focused either by a photographic plate or another mirror. The catadoptric combines elements of refractors and reflectors. Refractor optics are more resistant to misalignment but are limited in size. Reflectors do not suffer from chromatic aberration, but are easily misaligned and require frequent cleaning. More details are available in our article, Telescopes.

Microscope- A microscope (from the Ancient Greek: µ?????, mikrós, "small" and s??pe??, skopeîn, "to look" or "see") is an instrument used to see objects that are too small for the naked eye. The science of investigating small objects using such an instrument is called microscopy. Microscopic means invisible to the eye unless aided by a microscope.
There are many types of microscopes, the most common and first to be invented is the optical microscope which uses light to image the sample. Other major types of microscopes are the electron microscope (both the transmission electrlidon microscope and the scanning electron microscope) and the various types of scanning probe microscope

Types of microscopes
Microscopes can be separated into several different classes. One grouping is based on what interacts with the sample to generate the image, i.e., light or photons(optical microscopes), electrons (electron microscopes) or a probe (scanning probe microscopes). Alternatively, microscopes can be classed on whether they analyse the sample via a scanning point (confocal optical microscopes, scanning electron microscopes and scanning probe microscopes) or analyse the sample all at once (wide field optical microscope and transmission electron microscopes).
Wide field optical microscopes and transmission electron microscopes use the theory of lenses (optics for light microscopes and electromagnet lenses for electron microscopes) in order to magnify the image generated by the passage of a wave transmitted through the sample, or reflected by the sample. The waves used are electromagnetic (in optical microscopes) or electron beams (in electron microscopes). Resolution in these microscopes is limited by the wavelength of the radiation used to image the sample, where shorter wavelengths allow for a higher resolution.
Scanning optical and electron microscopes, like the confocal microscope and scanning electron microscope, use lenses to focus a spot of light or electrons onto the sample then analyze the reflected or transmitted waves. The point is then scanned over the sample to analyze a rectangular region. Magnification of the image is achieved by displaying the data from scanning a physically small sample area on a relatively large screen. These microscopes have the same resolution limit as wide field optical, probe, and electron microscopes.
Scanning probe microscopes also analyze a single point in the sample and then scan the probe over a rectangular sample region to build up an image. As these microscopes do not use electromagnetic or electron radiation for imaging they are not subject to the same resolution limit as the optical and electron microscopes described above.]\
The most common type of microscope (and the first invented) is the optical microscope. This is an optical instrument containing one or more lenses producing an enlarged image of a sample placed in the focal plane. Optical microscopes have refractive glass and occasionally of plastic or quartz, to focus light into the eye or another light detector. Mirror-based optical microscopes operate in the same manner. Typical magnification of a light microscope, assuming visible range light, is up to 1500x with a theoretical resolution limit of around 0.2 micrometres or 200 nanometres. Specialized techniques (e.g., scanning confocal microscopy, Vertico SMI) may exceed this magnification but the resolution is diffraction limited. The use of shorter wavelengths of light, such as the ultraviolet, is one way to improve the spatial resolution of the optical microscope, as are devices such as the near-field scanning optical microscope.
Sarfus, a recent optical technique increases the sensitivity of standard optical microscope to a point it becomes possible to directly visualize nanometric films (down to 0.3 nanometre) and isolated nano-objects (down to 2 nm-diameter). The technique is based on the use of non-reflecting substrates for cross-polarized reflected light microscopy.
CBP Office of Field Operations agent checking the authenticity of a travel document at an international airport using a stereo microscope
Ultraviolet light enables the resolution of microscopic features, as well as to image samples that are transparent to the eye. Near infrared light can be used to visualize circuitry embedded in bonded silicon devices, since silicon is transparent in this region of wavelengths.
In fluorescence microscopy, many wavelengths of light, ranging from the ultraviolet to the visible can be used to cause samples to fluoresce to allow viewing by eye or with the use of specifically sensitive cameras.
Phase contrast microscopy is an optical microscopy illumination technique in which small phase shifts in the light passing through a transparent specimen are converted into amplitude or contrast changes in the image. The use of phase contrast does not require staining to view the slide. This microscope technique made it possible to study the cell cycle in live cells.
The traditional optical microscope has more recently evolved into the digital microscope. In addition to, or instead of, directly viewing the object through the eyepieces, a type of sensor similar to those used in a digital camera is used to obtain an image, which is then displayed on a computer monitor. These sensors may use CMOS or charge-coupled device (CCD) technology, depending on the application.
Three major variants of electron microscopes exist:
• Scanning electron microscope (SEM): looks at the surface of bulk objects by scanning the surface with a fine electron beam. See also environmental scanning electron microscope (ESEM).
• Transmission electron microscope (TEM): passes electrons through the sample, analogous to basic optical microscopy. This requires careful sample preparation, since electrons are scattered so strongly by most materials.This is a scientific device that allows people to see objects that could normally not be seen by the naked or unaided eye.

eye pieces- An eyepiece, or ocular lens, is a type of lens that is attached to a variety of optical devices such as telescopes and microscopes. It is so named because it is usually the lens that is closest to the eye when someone looks through the device. The objective lens or mirror collects light and brings it to focus creating an image. The eyepiece is placed near the focal point of the objective to magnify this image. The amount of magnification depends on the focal length of the eyepiece.\

An eyepiece consists of several "lens elements" in a housing, with a "barrel" on one end. The barrel is shaped to fit in a special opening of the instrument to which it is attached. The image can be focused by moving the eyepiece nearer and further from the objective. Most instruments have a focusing mechanism to allow movement of the shaft in which the eyepiece is mounted, without needing to manipulate the eyepiece directly.
The eyepieces of binoculars are usually permanently mounted in the binoculars, causing them to have a pre-determined magnification and field of view. With telescopes and microscopes, however, eyepieces are usually interchangeable. By switching the eyepiece, the user can adjust what is viewed. For instance, eyepieces will often be interchanged to increase or decrease the magnification of a telescope. Eyepieces also offer varying fields of view, and differing degrees of eye relief for the person who looks through them.
Modern research-grade telescopes do not use eyepieces. Instead, they have high-quality CCD sensors mounted at the focal point, and the images are viewed on a computer screen. Some amateur astronomers use their telescopes the same way, but direct optical viewing with eyepieces is still very common.

Electrostatics What is charges?: this is a measure problem in physicl science, no body know, what is charge , only we know the propeties of charge . Coulomb’s law: according to coulomb’s law if two charge q1&q2piact at point A,B . r of the distance between point A&B .so according to coulomb’s law a face at attrection & repulstion force between charge q1&q2. k= constant of charge distribution r2= distance q1 q2= charge Three types of charge distribution: 1 Linear charge distribution: in this case , the charge is distributed along a line . if charge is distribution along a line , then we use a term liner charge density, which is defined as the charge per unit length. ++++++++++++++++++++++++++++++++ ?=q/L L q 2 surface charge distribution: if the charge is distribution over a surface, then this is know as surface charge distribution. This two dimensional distribution of charge. • =q/A
3    volume charge distribution:    volume charge density p is defined as the charge per unit volume, & it is used when charge is distributed uniformly along a volume .
? =q/v

  a region around charge q0  first  charge q1 in which another q0 q1 test charge q1 comes it files force of attraction & repulsion because of the effective field called electric field.

    If a test charge q0 is placed in an electric field and it experience electrostatic force, then electric field intensity or electric strength or simple electric field.
E=F/q0  or  F=E.q0
Electric potential : 
       The charge always flow from higher potential to lower potential region untill two charges reaches a common potential. Same as whether flow of upper level to lower level.
                      ?  E.l
EQUIPOTENTIAL SURFACE :    Equipotential means equal potential, so any surface has some electrostatics potential at every point is called equipotential surface.

ELECTRIC FLUX:       electric flux defivne as the total no. of electris lines of force crossing unit area normally. It is represents by f .

Unit of electric flux=m2(meter)2

GAUSS’S LAW:      The total flux from closed surface is equal 

ELECTRICAL CAPACITANCE:     electric capacity is defined as the ability of the conductor to store electric charge.
           q=CV   or    C=q/V    
A CAPACITOR & IT’S PRINCIPLE:       A capacitor is a device for storing large quantity of charge. The charge can be stored on an isolated conductor but its quantity is too small. To increase the charge reposition on conductor, two or more conductor are placed in such a manner that they  do not cover a large space, for it we require a capacitor. “An arrangement of two metallic conductor, so that when one connected on the earth, other has the ability to store a large amount of charge on it, is called a capacitor.

1.PARALLEL PLATE CAPACITOR: It is most common type of capacitor. It consist of two parallel plates P & Q which are placed at a distance of ‘d’ from each other.
               Let A be a area of cross section of each plate such that d<<A.
NOW, if +q charge is given to plate P, it will distributed uniformly on its surface due induction -q charge is include on the inner face on plate Q &  +q on its outer face. Since plate Q is connected to the ground.
2. SPHERICAL CONDUCTOR: A spherical conductor consist of two concentric spherical shells, separated by a very small distance. The spacing between the spherical shell may be filled by some dielectric medium increase the capacitance of the capacitor. 
                                         Spherical capacitor is shown, which consist of two spherical shells. The inner shell has radius ‘a’ & outer shell has ‘b’.
                                          Let +q charge be given to A, it distributes uniformly along it surface and due to induction q charge induces on the inner surface of B & +q on its outer surface. B is connected to ground.

3. CYLLINDRICAL CAPACITOR:     A cylindrical consists of two co-axial cylinders, out of two one is connected to earth and another is used to store charge on it. Both consists have a very small separation. 
                                                       Cylindrical capacitor is shown, which has two cylindrical shells A&B, having radii ‘a’ &’b’ respectively and length l.
                                                       Charge is given to A, charge –q induces on the inner surface of B and +q on the outer surface.

• SERIES COMBINATION :In this combination, first plate of the first capacitor is  connected to the source of charge, first plate of the second capacitor is connected to the second plate of the first capacitor then first plate of the third  capacitor is connected to second of the second capacitor and finally the second plate of the last capacitor  is connected to earth or connected to the second terminal of the souce.
        1/Cs = 1/C1 + 1/C2 + 1/C3  +  . . . . + 1/Cn               
                                      Thus when a number of capacitors are connected in series, then the reciprocal of the resultant or equivalent capacitance is equal to the sum of reciprocals of the individual capacitors.
                                         Obviously, cs is less than the smallest capacitance in the combination.

                                                   The capacitors are said to be connected in parallel, when the first of all the capacitors are joined together at one point A, which is connected to one terminal of the source & the second plate of all the capacitors are joined together at another point B, which is either connected to earth or connected to the second terminal of the source. 
                       In a parallel combination potential difference across each capacitor remain & is equal to the potential difference produced by the source & charge is distribute.
                        Cp = C1 + C2 + C3 + . . . . + Cn
                                  Thus, when a no. of capacitors are connected in parallel, then the resultant or equivalent   capacitance  is equal to the sum of capacitance of all e capacitors use in combination. The resultant capacitors  in a parallel combination is always more than the capacitance of individual capacitor.


CURRENT ELECTRICITY:    In unit time the charge given to conductor equal to electric current.
                           I = q/t    or    I = ne/t
                       Coulomb/sec = Ampere(unit)

                                   Drift velocity is the velocity acquired by the electrons present in a conductor on applying an electric field across the two ends of the conductor. This velocity is in addition with random motion. 
                                                 If  v1 + v2 + v3 + . . . + vn are the random thermal velocities of n electrons present in an conductor, then average thermal velocity of the electrons 
                                  ( V1 + V2 + V3 + . . . + Vn)/n = 0

                             In normal condition of  temperature & pressure if electric current is given to any conductor then it directly proportional to electric potential also increase depend of resistant conductor.
                                Unit of resistant is ?(ohm)
                                     1 ? = V/A(ampere)
ELECRICAL RESISTIVITY: basically resistance is the obstacle created by the atoms or moles of the the conductor in flow of current; it means the resistance obstructs the flow of electrons.
               The resistance of any conductor is 
• directly proportional to its length 
                                         R  l
• inversely proportional to the area of cross section of the conductor
                          R  1/A
            Thus      R l/A

                            R = ? (l/A)
    Unit of ? = ?-m

                                                    The reciprocal of the electrical resistance is known as  electric conductance or simply conductance of the conductor. Since the resistance obstructs the flow of e-s in a conductor & hence the conductance allows to flow the e-s through the conductor.
 Thus, the conductance of a conductor is given by 
                                  C = 1/R 
     Unit of electrical conductance is mho or ohm-1.

                                                   The relation between resistivity & conductivity is inversely proportional to each other.
              Thus = 1/ ?


                          conductor are those elements, which contains sufficient amount of free electrons. In these valence band & conductance band overlap, so we don’t require energy for the flow of e-s
Examples: silver, copper, iron, aluminium .

                      insulators are those elements, which does not contain free electrons in conduction band and the energy difference between valence band and conduction band is sufficiently large. Thus, insulator have very high resistivity & very low  conductivity.
Example: glass, wood, rubber.

                                  They having conductivity less than the greater  than the insulator. At room temperature, so at room temperature semiconductor , conducts electricity. 

Example: ge & si are very commonly used to semiconductor.

“B B ROY of Grate Brition Hase A Very Good Wife”
colour Number multiplier Tolerance
Black 0 10 0 -
Brown 1 10 1 -
Red 2 10 2 -
Orange 3 10 3 -
Yellow 4 10 4 -
Green 5 10 5 -
Blue 6 10 6 -
Violet 7 10 7 -
Grey 8 10 8 -
White 9 10 9 -
Gold - 10-1 5%
Silver - 10-2 10%
No colour - - 20%

                                           This combination is used to increase the value of resistance. In this method two or more resistors are connected in such a way that the second terminal of first resistors is connected to the first of, similarly second terminal of second resistors is connected to the first terminal of third  resistors and so on. Finally first terminal of first resistor and second terminal of the last resistor are connected to a battery.
      In this type of combination the current passes through each resistor is the same.
                                                     This is another combination of connecting resistance. This combination is basically used to becrease the value of resistance. In this type of combination first terminal of each resistors are connected together, similarly second terminals of each resistors are also connected together. 


                                             It states that  the algebric  sum of electric currents meeting at a point in an electrical circuit is always zero. It is also known as junction.
                                             The current flowing towards the junction point is taken as +ve, while the flowing always from the junction point is taken as –ve.
                                       This law is also known as kirchhoff’s current law (KCL).
                                                   This law is basically known as loop rule, since it is valid for closed part only. According to this law the algebraic sum of the emf in any part of the circuit is equal to the sum of the potential difference across the resistance available in that part. 
                                       ?E = ?IR 
                             This law is also known as kirchhoff’s voltage law (KVL). 

                                                According to this theorem “any two terminal linear network containing linear impedances and one or more generators can be replace d with an equivalent circuit consisting of an equivalent in series with an emf”.

                                         This theorem states that the current in a load impedance ZL connected to two output terminals of a network consisting of one or more generators and impedances is the same as if the load impedance were connected to a constant current source in shunt with an impedance Zeq.

             According to this theorem the power delivered to the load or external circuit will be maximum only when the load resistance is equal to the internal resistance of the network delivering the power.

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