Research topics in physics pptx

Physics Physics has an important role in our life. Without physics and the work of physicists, our modern life would not exist. Using physics, people created machines, instruments and some different divices from the crudest to the most modern aspect. Techology is developed more rapidly, more modern day by day. Moreover, all other natural sciences- example chemistry, biology, medicine- depend upon physics for the foundations of their knowledge. Physics holds this key position because it is concerned with the most fundamental aspect of matter and energy and how they interact to make the physical universe. Physics has some main problems: mechanics, electricity and magnitism, heat, wave and sound, optics, nuclear physics, atomic particles. CHAPTER 1: MECHANICS Mechanics is a branch of physics concerned with the behavior of physical bodies under the effect of the bodies on their enviroment. The early modern period, scientists, such as Galileo, Kepler and especially Issac Newton, laid the foundation for a field of mechanics and now it is known as classical mechanics or Newtonian mechanics. Mechanics has two major divisions: classical and quantum mechanics. Classical mechanics came first while quantum mechanics did not appear until 1900. Both commonly constitute the most certain knowledge that exists about physical nature. Classical mechanics is concerned with the physical laws governing the motions of bodies. It is used for describing the motion of marcroscopic objects, such as: parts of machinery, astronomical objects inclue spacecraft, planets, stars, galaxies. It is one of the oldest and lagest subjects in science, engineering and technology. Classical mechanics is divided into: statics, dynamics and kinematics. Statics studies matter at rest or in motion with constant velocity. It deals with the balancing of forces with approriate resistance to keep matter at rest. It is commonly used for designing buildings and bridges. Different from statics, dynamics studies matter in motion, example motion of stars, baseballs, gyroscopes of the water pumped, and even air plane. Kinematics studies motion without regard to the forces present. It is simply a mathematical way to describe motion. Three Newton’s laws: Classical mechanics is governed by three basic principles, which were first formulated in the 17 th and 18 th centuries by Isaac Newton. These principles are known as Newton’s laws. The first law describes a fudamental property of matter, and often called the “Law of Inertia”, as follows: Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it. The key point here is that if there is no net force acting on an object (if all the external forces cancel each other out), the object will maintain a constant velocity, if that velocity is zero, the object remains at rest and if having an external force to apply, the velocity will change. Newton’s second law describes the manner in which a force compel a change of motion, at a rate of change called acceleration. It can be state as follows: F=ma Where F: the applied force m:mass of the object a: the object’s accerleration Acceleration and force are vectors, in this law the direction of the force vector is the same as the direction of the acceleration vector. This law allows quantitative canculations: how do velocity change when forces are applied. Notice the fundamental difference between Newton’s 2 nd law and the dynamics of Aristotle: according to Aristotle there is only velocity if there is a force, but according to Newton an object with certain velocity maintains that velocity unless the force acts on it to cause an acceleration. Newton’s third law can be stated as follows: For every action in nature there is an equal and opposite reaction. In other words: if object A exerts a force on object B, then object B also exerts an equal force on object A. Notice that the forces are exerted on different objects. This law explains what happens if we step off a boat onto the bank of a lake: as we move in a direction, the boat tends to move in the opposite direction. Mass, force and acceleration Mass is the amount of matter in a body. The mass of a body remains constant. In the metric system mass is measured in kilogram (kg). Sometimes we use weight, or the pull of gravity upon matter. The object’s weight depends on the gravitational pull acting on it. An object’s weight is much less on the moon than it is on the Earth, and in outer space a body’s weight may be nearly zero. When an object’s velocity changes, it accelerates. Acceleration shows the change in velocity of a body in a unit time. According to Newton’s 2 nd law, it is direct result of the applied force. In the metric system, acceleration’s unit is (m/s)/s. When we study mechanics, we can know a concept: force. Force is a vector quantity that has both a specific magnitude ( size or length) and direction. It is characteristic for a body’s acting to other. It changes the motion of a free body or cause stress in a fixed body. It can also be described by concepts such as a push or pull that can cause an object with mass to change its velocity, to accelerate, to deform. If two forces applied simultaneously to the same point have the same effect as a single equivalent force, called resultant force. We can canculate the net force: F=F1+F2+… . If two forces acting on an object is the same direction (parallel vectors), the resultant force is equal to F1+F2, in the direction that both two forces. If two forces acting on a object is opposite directions, the net force is equal to |F1-F2 |, and direction of whichever one has greater magnitude. If the angle between the forces is anythingelse, the net force must be added up using the parallelogram rule. The same forces can have different effects depending on applied way and applied body. A force may cause a body to spin or rotate if applying in a certain way. The tedency of a force to rotate the body is known as torque, it is also a vector quantity. Its magnitude can be calculated by multiplying applied force to the distance between the line of force and the axis of rotation. A kind of force which resists the motion of a body along a path is friction. It appears only when other forces are applied or if a body is already in motion. It may be undersirable in some cases, example: air resistance that slows down an airplane, but in some other cases, it is useful, example: car brakes. Center of gravity and equilibrium : It’s difficult to apply the laws of mechanics to a particular body. The problem is more simple if we study the behavior of an object’s center of gravity instead of studying the behavior of entire pbject. The center of gravity is a point at which the weight of a solid object can be considered to be concentrated . all forces appear to act upon this center. If the line of exerted force does not pass through the center of gravity, a torque is created. A body can be completely at rest if all forces and all torques are balanced. A complete balance exists. If the sum of all forces and torques acting on a body is equal zero, we say that the body is in equilibrium. A body in equilibrium may be in one of three states: stable, unstable, neutral equilibrium. When a torque apply to a body, after the torque ceases to act, if the body tends to return to its original position, it is in stable equilibrium. If it continues to turn to a new position, it is known as unstable equilibrium. The body is in neutral equilibrium if it comes to rest wherever it may be when the torque is removed. Work, energy and power Work: when a force makes a body move, the product of the force times the distance through which the force acts is called the work done by the force. There are some example of work which we can observe in everyday life: a horse pulling a plow through the field, a man pushing a cart, a weightlifter lifting e barbell above his head, etc. Mathematically, work can be canculated by the following formula: A=F d cosα Where F: the force ( in Newton) d: the distance through which the force acts (the displacement), (in meters) α : the angle between the force and the displacement vector. Energy is the capacity for doing work. If work is done on a body, the energy of the body increases. Energy is consists of kinetic and potential energy. Energy associated with motion is kinetic energy. It is equal to one half the product of its mass times the squre of its velocity represented by a formula: KE = (1/2)mv 2 Where: KE: kinetics energy (in Joule) m: mass ( in kg) v: velocity (in m/s) Potential energy exists whenever an object which has mass has a position within a force field. The most everyday example of this is the position of objects in the earth’s gravitational field. In this case, the potential energy of an object is given by: PE = mgh Where: PE: potential energy ( in Joules) m: mass ( in kg) g: gravitational acceleration of the earth ( 9.8 m/s/s) h: height above earth’s surface ( in m) Conservation of energy This principle asserts that in a closed system energy is conserved. This principle will be tested by the experiment in the case of an object in free fall. When the object is at rest at height h, all of its energy is PE. As the object falls and accelerates due to the earth’s gravity, PE is converted into KE. When the object strikes the ground, h=0, so that PE=0, the all of the energy has to be in the form of KE and the object reaches the maximum velocity. In this case we are ignoring air resistance. Power is the rate of doing work or the rate of using energy. Unit of power is watt. If we do 100 joules of work in one second ( using 100 joules of energy), the power is 100 watts. Some simple machines. Many principles of mechanics are clearly demonstrted in devides called simple machines. These machines have been known since antiquity with crude machines or now with modern machines. They are the lever, the wheel and axle, the inclined plane, the screw, the rope-and-pulley system. They are designed to amplify the effect of forces or to do work to move weight or to overcome resistances. Chapter 2: Heat Definition and applications All living things need heat. Heat is a form of energy transferred from one object to another caused by a different in temperature between these objects. Some other words: - Heat is defined as energy in transit from a high-temperature object to a lower one. - Heat is a form of energy possessed by a substance by virtue of the vibrational movement of its molecules or atoms. - Heat is the transfer of energy between substance of different temperatures. Heat has an important role in our life. It causes natural changes which occur in an endless cycle. To explain some phenomena in the nature, we can use concept of heat. Example the atmosphere in tropical areas is hotter than it in polar areas because tropical areas receive more heat from sun. The amount of heat from the sun that falls on the region determines the temperature range of the region. The temperature of environment effect to plant, animal and even man. Heat is a very important factor in making our life and our world. The nature of heat. Despite having many definitions of heat, heat has one nature. We can know heat when we were a child. We could detect it easily through its effect: burning. But do you know what heat itself actually is? Heat cannot be weighed and cannot be seen or heard too. To understand the nature of heat, we may study its acting, we can use the kinetic theory of matter. According to this theory, all matter made of atoms and molecules in constant motion. When matter absorbs energy, the random internal energy and the motion of these atoms and molecules are increased. This increase makes itself in the form of heat, and when it occurs, the temperature of the matter rises. This leads a conclusion: when the energy of motion has been transferred to the random motion of the atoms that make up the matter, the motion of the atoms is speeded up and heat is produced. That is the nature of heat. Sources of heat Heat is very necessary for life, so it is important to know where it comes from and how it can be used. The most important source of heat for our Earth is the radiation from the sun. The Earth absorbs a part of heat from the sun. This keeps the temperature of the Earth’s surface and atmosphere at a level which permits life to continue. The second important source of heat is the store of natural fuel on and in the Earth, such as: coal, oil, gas, wood. They do not provide heat constantly and automatically as the sun does. They are composed of carbon, hydrogen, and other elements. In a certain temperature, the combustion occurs, the fuels react chemically with oxygen. This reaction releases a large quantity of heat. The definition of specific heat. The specific heat is the amount of energy that is transferred to or from one unit of mass or mole pf a substance to change its temperature by one degree. Specific heat is a property, it depends on the substance under consideration and its state. The temperature Temperature is the property that gives physical meaning to the concept of heat. And object has low temperature if it is cold, and vise versa. When contacting with a cold body, a hot body gives up some of its heat to the cold one. The process will continue until both have the same temperature. Definition of temperature is based on some constant value, absolute zero. Absolute zero is defined as the temperature at which all molecules and atoms’ motion stops completely. It is equal to -273.16 Celsius or 0 Kelvin. We can define temperature as: temperature of a substance is a measure of the intensity of motion of all atoms and molecules in that substance. To measure temperature, we use the themometer scale. Its working is based on the fixed points of boiling water and freezing water. There are four scales: Fahrenheit, Celsius, Kelvin, Rankine. We can change from this scales to different one. Some useful conversation relation: Fahrenheit to Celsius: T(C)=5/9(T(F)-32) Celsius to Fahrenheit: T(F)=9/5 (T(C)+32) Celsius to Kelvin: T(K)=T(C) + 273 Fahrenheit to Rankine: T(R)=T(F)+460 Kinetic Theory Heat is not a material fluid. It is the result of a conversion of energy. It is a form of energy. It is equivalent to mechanical energy. We have a conversation: one calorie of heat energy is equal 4.184 joules of mechanical energy. In an isolated system, work can be converted into heat at ratio of one to one. Three laws of thermodynamics: The zeroth law: Energy can be only transferred by heat between objects (or areas within an object) with different temperature. The first law: in an insolated system, work can be converted into heat at ratio of one to one. The second law: Heat transfer happens spontaneously only in the direction from the hotter body to the colder one. The Transfer Of Heat Heat transfer helps to shape our world. Heat always travels or flows from a high temperature to a low temperature. In the nature, there are three different methods of transfer heat. They are: radiation, conduction, and convection. Radiation Radiation is a process of transferring heat energy from one place to another. This process occurs when the internal energy of a system is converted into radiant energy at a source such as heater. This energy is transmitted by invisible wave through space. Example the sun radiate heat outwards through the solar system. Finally the radiant energy touch a body where it is absorbed and converted to internal energy. And then heat appears. By radiation, heat only travels in space or in gases. All bodies, whether hot or cold, radiate energy. The hotter a body is, the more energy it radiates. A body at constant temperature radiate energy continously. It is receiving energy at the same rate that is radiating energy. So it doesn’t change in internal energy or temperature. Radiation transfer depends upon the shape of the radiating object. It is not proportional to the difference in temperature between two object but it is proportional to the fourth powers of the absolute temperature. Conduction Conduction is the most significant means of heat transfer in a solid. If one part of a body is heated by direct contact with a source of heat, the next parts become heated. This may be explained by the kinetic theory of matter. When the temperature increases, heat motion of molecules raises, this violent motion passes along the body from this molecule to another and result: the body is heated and this process is known as conduction. Example, if dipping simultanously a silver and a wood spoon into boiling water, the handle of the silver one rapidly becomes hot while the wood one still is cool. Materials in which heat transfer happens easily and quickly are known as good conductors, example all metals. In meterials such as wood, rubber and air, heat is not transferred readily from one molecule to the next, they are called insulators. Conduction occurs readily in good conductors of heat. Conduction depends upon the different of temperature and the resistance of the flow of heat. The greater the temperature difference between two point is, the more the driving force to move heat is. The less resistance is, the easier heat transfer is. Convection The third method of heat transfer is covection. It happens in liquids or gases (commomly called fluids). Convection occurs when having the change of density (mass per unit volume). If heating fluid, its density decreases, so it becomes lighter. The part of warmer fluid will rise while the part of colder will decend. This process happens continously until having balance in temperature. Some examples in the fact: water in a kettle is heated by convection; the air in the room is heated by convection when putting a stove in that room; or when we drop a few crystals of potassium permanganate into water, we can see movement of pink water, convection occurs. Chapter 3: Electricity Electricity is a general term heat emcompasses a variety of phenomena resulting from the presence and flow of electric charge. These inclue many easily recognizable phenomena, such as lightning and static electricity. In general usage, electricity refers to a number of physical effects. However, in scientific usage, it inclues these related concepts: eletric charge, electric current, electric field, electric potential difference, electromagnetism. Electrical phenomena have been studied since antiquity. Until the 17 th and 18 th centuries, advances in the science were not made. And until the late 19 th century, engineers were able to put it to industrial and residential use. The rapid expansion in electrical technology at this time transformed industry and society. Electricity almost has no limits, it can go anywhere, even far into space. It has applications in transport, heating, lighting, communications and computation. We cannot imagine today’s world without it. Electricity keeps an important role in our world. Electric Charge Electric charge is a property of subatomic particles, it determines those particles’ electromagnetic interactions. Charge originates in the atom. Atoms cotains two kinds of charge: negatively charged electrons and positively charged protons. In an isolated system, charge is a conserved quantity. Within the system, charge may be transferred between bodies following two ways: direct contact or passing along conducting material. The informal term static electricity refers to the net presence of charge on a body, usually caused when rubbing dissimilar together, transferring charge from one to another. A light-weight ball suspended from a string can be charged by touching it with a glass rod that has been charged by rubbing with a cloth. If a similar ball is charged by the same glass rod, two balls will repel each other. They also repel each other if they are charged by rubbing with an amber rod, and the other by an amber rod, two ball attract each other. These phenomena were investigated in the late 18 th century by Charles Augustin de Coulomb. He discovered the well-known conclusion: like charges repel and unlike charges attract each other. He gave a law to show the relationship between amount of electric force that two charged objects exert upon each other and the distance separating them, called Coulomb’s law. This law is stated by the formula: Where: r: the distance between two charges k: a constant for converting units of charge and the distance into units of force q1,q2: charges of two objects. The charge on electrons and protons is opposite in sign. The mount of charge is usually given the symbol q, and its unit is coulombs (C). Each electron carries the same charge, about -1.6022.10^-19 (COP TREN MANG NHE), and the proton is +1.6022… In a atom, if numbers of protons and electrons are equal, the atom is neutral. If a neutral loses electrons, it has an excess number of protons and it is positively charged. If a neutral atom gains electrons, it has an excess number of electrons and it becomes negatively charged. Electric Current An electric current is the movement of electric charge. This moving charge may be electrons, protons, ions, even positive “hole” in semiconductors. We calculate the current by the formula: Where Q: the total charge ( in coulombs) t: the time (in seconds) The current I is measured in amperes. A one-ampere current means that one coulombs of electric charge passes each point in the circuit each second. Addition to coventional current has been described as the direction of positive charge motion. Electric Field The concept of electric field was introduced by Michael Faraday in the 19 th century. Electric field is space that surrounds a charged object and exerts a force on any other charges placed within the field. We all know that charged object can exert forces on uncharged objects over a distance. We use the electric field to describe possible effects at a point in space about an electric charge. An electric field generally varies in space, its strength at a point E is defined as: E=F/q Where F: the electric force on a test charge q: the size of the test charge placed at that point The electric field strength is a vector quantity, having both magnitude and direction. Specifically it is a vector field. The study of electric field created by stationary charges is called electrostatics. The field may be visualized by a set of imaginary lines. These lines give an overview of the electric field, their direction at any point is the same as that of the field. These lines are called “lines of force”. This concept was introduced by Michael Faraday. The field lines are the parths that a point positive charge would to seek to make as it was forced to move within the field. They have key properties: - They originate at positive charges and end at negative charges - They must enter any good conductor at right angles - They may never cross nor close in an themselves. Electric Potential Placing a positive test charge near a fixed positive point charge, it will accelerate away and increase in velocity and klinetic energy. But to move this positive test charge back toward the fixed positive charge, we must do a work on the test charge. The energy put into this process is stored as electric potential energy. The electric potential at any point is the energy required to bring a unit test charge from an infinite distance slowly to that point. It is measureed in volts, one volt is the potential for which one joule of work must be done to bring a charge of one coulomb from infinity. In the fact, we don’t often use this concept. A more useful concept is that of electric porential difference. It is a measure of this change in energy as the charge moves from one place to another in an electric field. It is given by defining energy change to charge moved. Its unit is volt. Sometimes it called voltage. When the voltage is zero ( or electrical potential between points in a field is not different), electric charge does not move between those points. When potential different between two points in a field is large, positive electric charge will tend to move from higher to lower potential and negative charge will move the opposite way. Electromagnetism In 1821, the Danish scientist Han Christian Oersted discovered magnetic field that existed around all sides of a wire carrying an electric current. If bringing a compass near a current carrying wire, its magnetized needle would realign. If the current is reversed in direction, the compass needle reverse its orientation. A magnetic field is created arround the current-carrying wire. We can represent this magnetic field as a series of concentric field lines in planes perpendicular to the current, called the magnetic field lines. When the direction of current is known, we can use the right-hand rule to find the field direction. That rule can be stated as: put the right hand with the thumb pointing in the direction of current and the finger encircles the wire, the magnetic field lines are the same direction as the fingers. Or we can predict the field direction by using a magnet: the direction of the magnetic field is from north to south pole of magnet. Magnetism and electricity have a direct relationship. A current exerts a force on a magnet and a magnetic field exerts a force on a current. Magnetism is induced by an electric current is known as electromagnetism and the field which it works is callled electromagnetic field. Ampere investigated the relationship between electricity and magnetism. And he discovered that two parallel current carrying wires exerted a force upon each other: two current in the same direction attract each other, and vise versa, currents in positive direction repel each other. Electric Circuit A basic circuit can be described as: the voltage source, example battery, is connected with a resistor R through wires, a current I from the source transfer through the resistor, and from the resistor, the current returns to the source. An electric circuit is produced. If the source is the a battery, between the terminals of the battery there is a potential difference, under acting this potential, electrons flow in one direction, away from the negative terminal toward the positive. The current has a direct relationship to the voltage of the battery, and it depends on the nature of the conductor. This relationship is shown in Ohm’s law which was stated in the 19 th century by Georg Simon Ohm. This law is given by a formula: U = IR Where I : the current ( in amperes) U : the potential difference (in volts) R : the resistance (in ohms) Chapter 3: Optics Optics is the branch of physics which studies the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behavior of visible, ultraviolet, and infrared light. Most optical phenomena can be accounted for using the classical electromagnetic description of light. However complete electromagnetic descriptions of light are often difficult to apply in practice. Practical optics is usually done using [...]... when passing from air to glass In daily life, we can observe total internal reflection while swimming, if we open our eyes just under the water’s surface We ourselves can do experiments to represent this phenomenon Physical Optics Looking again at the ray picture of focusing above, we run into a problem: at the focal point, the rays all intersect The density of rays at this point is therefore infinite,... to the discovery that light waves were in fact electromagnetic radiation Optical science is relevant to and studied in many related disciplines including astronomy, various engineering fields, photography, and medicine (particularly ophthalmology and optometry) Practical applications of optics are found in a variety of technologies and everyday objects, including mirrors, lenses, telescopes, microscopes,... which according to geometrical optics implies an infinitely bright focal spot Obviously, this cannot be true If we put a black screen in the plane of the focal point and look closely at the structure of the focal spot projected on the plane, experimently we would see a very small central bright spot, but also much fainter rings surrounding the central spot These rings cannot be explained by using the geometrical... ray can be described clearly by Snell’s law, as following: sin 1 v1 n2   sin  2 v2 n1 or n1 sin 1  n2 sin  2 Or in the words, when a light ray passes from one medium to another, the ratio between the sine of the angle of incidence and the sine of the angle of refraction is constant From the laws of reflection and refraction, we can determine the behavior of optical devices such as telescopes... convex lens is a converging lens This kind of lens is thicker in the middle and thinner towards the edges, like the lens in a magnifying glass The image is changed by the position of the object in relation to the focal length and the radius of curvature If the object is beyond 2F, the image is real, inverted and reduced, at 2F real, inverted and the same height, between F and 2F real, inverted, and magnified,... boundary surface, and a remaining part will be reflected If the angle of the incidence is greater than the critical angle, the light will stop crossing the boundary altogether and instead be totally reflected back internally This can only occur when light travels from a medium with a higher refractive index to one with a lower refractive index For example, it will only occur when passing from glass to air,... different rays are refracted through different angles A simple lens is a lens consisting of a single optical element Most of lenses are typically made of glass or transparent plastic A beam of parallel rays can be caused to converge at a single point or diverge from a single point This point is called the focal point of the lens If the light rays converge when they pass through a lens, a real image... thought to be four main forces in nature, and two of them could not be mathematically define In the late 1980s scientists devised a hypothesis about the existence of a fifth fundermental force in nature And in the early 1990s, by experiments, they concluded exactly the existence of a fifth fundermental force In addition, scientists have developed techniques to probe more deeply into structure of matter... composed of two protons and two neutrons Composite particles include all hardrons, a group composed of baryons and mesons There are hundreds of known subatomic particles, and most are result of cosmic rays interacting with matter, or have been produced by scattering processes in particle accelerators Nuclear Physics Nuclear physics is the field of physics It deals with the study of the properties of nuclei... and laws of nature It has applications in the generation of electrical power, in the treatment of cancer and other diseases, and in the developmnet of nuclear weapons, among many others Its applications have been a major influence in the course of human history When studying nuclear physics, we must note to nuclear energy, an important source of energy now and in the future The energy that the sun and . Looking again at the ray picture of focusing above, we run into a problem: at the focal point, the rays all intersect. The density of rays at this point is therefore infinite, which according. continously until having balance in temperature. Some examples in the fact: water in a kettle is heated by convection; the air in the room is heated by convection when putting a stove in that. were in fact electromagnetic radiation. Optical science is relevant to and studied in many related disciplines including astronomy, various engineering fields, photography, and medicine (particularly