Showing posts with label Physics. Show all posts
Showing posts with label Physics. Show all posts

GRE Subject Test: Physics

What is the test pattern for GRE Physics

  • No. of Questions: 100 Five-Choice Questions
Syllabus and Test Pattern

    CLASSICAL MECHANICS — 20%
    (such as kinematics, Newton's laws, work and energy, oscillatory motion, rotational motion about a fixed axis, dynamics of systems of particles, central forces and celestial mechanics, three-dimensional particle dynamics, Lagrangian and Hamiltonian formalism, noninertial reference frames, elementary topics in fluid dynamics)
    ELECTROMAGNETISM — 18%
    (such as electrostatics, currents and DC circuits, magnetic fields in free space, Lorentz force, induction, Maxwell's equations and their applications, electromagnetic waves, AC circuits, magnetic and electric fields in matter)
    OPTICS AND WAVE PHENOMENA — 9%
    (such as wave properties, superposition, interference, diffraction, geometrical optics, polarization, Doppler effect)
    THERMODYNAMICS AND STATISTICAL MECHANICS — 10%
    (such as the laws of thermodynamics, thermodynamic processes, equations of state, ideal gases, kinetic theory, ensembles, statistical concepts and calculation of thermodynamic quantities, thermal expansion and heat transfer)
    QUANTUM MECHANICS — 12%
    (such as fundamental concepts, solutions of the Schrödinger equation (including square wells, harmonic oscillators, and hydrogenic atoms), spin, angular momentum, wave function symmetry, elementary perturbation theory)
    ATOMIC PHYSICS — 10%
    (such as properties of electrons, Bohr model, energy quantization, atomic structure, atomic spectra, selection rules, black-body radiation, x-rays, atoms in electric and magnetic fields)
    SPECIAL RELATIVITY — 6%
    (such as introductory concepts, time dilation, length contraction, simultaneity, energy and momentum, four-vectors and Lorentz transformation, velocity addition)
    LABORATORY METHODS — 6%
    (such as data and error analysis, electronics, instrumentation, radiation detection, counting statistics, interaction of charged particles with matter, lasers and optical interferometers, dimensional analysis, fundamental applications of probability and statistics)
    SPECIALIZED TOPICS — 9%
    Nuclear and Particle physics (e.g., nuclear properties, radioactive decay, fission and fusion, reactions, fundamental properties of elementary particles), Condensed Matter (e.g., crystal structure, x-ray diffraction, thermal properties, electron theory of metals, semiconductors, superconductors), Miscellaneous (e.g., astrophysics, mathematical methods, computer applications)

General Knowledge for Competitive Examinations

General Knowledge (GK) makes Integral Part of many competitive examinations in India. The GK Test examine your awareness and abilities from in and around your surroundings. In this portion questions are asked from day to day life experiences. Generally, whether its and admission test or recruitment exam questions are asked from the areas those we discuss often among friends, family, or listen over radio, television and social media etc.

General Knowlegde: PHYSICS

Perhaps everyone know Einstein. Physics is the science that make you immortal. Personally I divide PHYSICS in two phases; Physics before Einstein and Physics after Einstein. General Knowledge of Physics is the study discipline everyone should know and understand. In competitive examinations like Bank PO, SSC, Railways, UPSC Exam, Scholarship Test, Admission Test etc  GK Questions are asked in PHYSICS. Here are general lessons in physics useful for writing selection test / admission test etc.

Units

List of Scientific Instruments and Uses

Inventions, Inventor, Country and Year

Important Physics Discoveries in Chronology Order

Electronics



Electronics – Electronics is the branch of physics and technology that deals with the emission, behavior, and effects of electrons and with electronic devices.

Most electronic devices use semiconductor components to perform electron control. The study of semiconductor devices and related technology is considered a branch of solid state physics, whereas the design and construction of electronic circuits to solve practical problems come under electronics engineering. This article focuses on engineering aspects of electronics.

Timeline: Nuclear Treaties & Agreements

1963 Limited Test Ban TreatyAn agreement between the US, USSR, and UK which prevented nuclear testing above ground, underwater, and in outer space. But it does allow testing to occur underground as long as the radioactive fallout is not widespread. A total of 116 countries have signed this, and China, who had not signed, did testing in 1992 that violated the treaty's guidelines.

Chronological Developments in Nuclear Physics

1890s
1895
November 8 - Wilhelm Roentgen discovers X-Rays
1897
Becquerel and Marie Curie discover radioactivity
1895 - 1899
Ernest Rutherford discovers alpha and beta radiation
1898
Marie and Pierre Curie isolated the two new chemical elements polonium and radium

Atomic and Nuclear Physics



Atoms - Atoms are the smallest unit of an element that chemically behaves the same way the element does. When two chemicals react with each other, the reaction takes place between individual atoms at the atomic level.

Atomic Structure

  • In the early 20th century, a New Zealand scientist working in England, Ernest Rutherford, and a Danish scientist, Niels Bohr, developed a way of thinking about the structure of an atom that described an atom as looking very much like our solar system.
  • An atom is composed of three basic particles – electrons, protons and neutrons.
  • Nucleus of an atom consists of protons and neutrons.
  • Electrons revolve in atomic orbit.

Magnetism



Magnetism - Magnetism is a force of attraction or replusion that acts at a distance. It is due to a magnetic field, which is caused by moving electrically charged particles or is inherent in magnetic objects such as a magnet.

Magnetism - A magnet is an object that exhibits a strong magnetic field and will attract materials like iron to it. Magnets have two poles, called the north (N) and south (S) poles. Two magnets will be attacted by their opposite poles, and each will repel the like pole of the other magnet. Magnetism has many uses in modern life.

Current Electricity

Electric Current - The Electric current is a flow of electric charge through a conductive medium.

In electric circuits this charge is often carried by moving electrons in a wire. It can also be carried by ions in an electrolyte, or by both ions and electrons such as in a plasma.

The SI unit for measuring the rate of flow of electric charge is the ampere, which is charge flowing through some surface at the rate of one coulomb per second. Electric current is measured using an ammeter.

Static Electricity

Static electricity is an excess of electric charge trapped on the surface of an object. The charge remains until it is allowed to escape to an object with a weaker or opposite electrical charge, such as the ground, by means of an electric current or electrical discharge. Static electricity is named in contrast with current electricity, which flows through wires or other conductors and transmits energy.

Light

Light is a type of energy which propagates as electromagnetic waves. In the spectrum of electromagnetic waves, light has place between ultraviolet and infrared region.

Some Facts About Light

•    Electromagnetic waves are transverse waves, therefore, light is also transverse wave.
•    Wave nature of light explains; rectilinear propagation of light, reflection of light, refraction of light, interference of light, diffraction of light and polarization of light.
•    The happenings in physics like Photoelectric Effect and Compton Effect can not be explained on the basis of wave nature of light. These phenomenons are explained on the basis of quantum theory of light, explained by Albert Einstein.
•    The quantum theory of light, considers light as a packet or bundle of energy, these energy packets are called photons. Photon associates with it as Energy E; where E = hv
•    Light has dual nature and behaves as a particle as well as wave.
•    Speed of Light was first calculated by Roemer in 1678 AD.
•    Speed of light is maximum in vacuum, which is equivalent to 3x108 m/s.

Thermodynamics

First Law of Thermodynamics


The first law of thermodynamics is the application of the conservation of energy principle to heat and thermodynamic processes:

The change in internal energy of a system is equal to the heat added to the system minus the work done by the system.

Mathematically, ΔU (Change in Internal Energy) = Q (Heat added to or drawn from the system) – W (Work done by the system)

Heat

Heat may be defined as energy in transit from a high temperature object to a lower temperature object.

Some Characteristics of Heat and Mathematical Equivalent


•    Heat is also defined as the transfer of kinetic energy from one medium or object to another, or from an energy source to a medium or object.

•    The heat transfer can occur in three ways: radiation, conduction, and convection.

•    The standard unit of heat in the International System of Units (SI) is the calorie (cal).

•    One calorie is defined as the amount of energy transfer required to raise the temperature of one gram of pure liquid water by one degree Celsius, provided the water temperature is higher than the freezing point and lower than the boiling point.

•    Sometimes the kilocalorie (kcal) is specified as a unit of heat; 1 kcal = 1000 cal. This is the also called diet calorie.

•    The amount of heat contained in a body depends upon the mass of the body.

•    If W is work performed and Heat produced is H, then W/H = J or W = JH, where J is a constant called mechanical equivalent of heat. The value of J is 4.186 Joule / Calorie. This means if 4.186 Joule of work is done, 1 Calorie of heat is consumed.

Sound Waves

•    Sound is a mechanical wave that results from the back and forth vibration of the particles of the medium through which the sound wave is moving.
•    If a sound wave is moving from left to right through air, then particles of air will be displaced both rightward and leftward as the energy of the sound wave passes through it.
•    The motion of the particles is parallel (and anti-parallel) to the direction of the energy transport. This is what characterizes sound waves in air as longitudinal waves.
•    The mechanical vibrations which can be said as sound are able to travel through all forms of matter i.e. solids, liquids and gases. The matter which allows the sound to travel through it is called the medium.
•    Sound cannot travel through a vacuum.

Wave

Wave- A wave can be described as a disturbance that travels through a medium from one location to another location without the transport of matter.

Types of Waves
Waves can be said of two types – 1. Mechanical Wave and 2. Non – Mechanical Wave

Simple Harmonic Motion

Periodic Motion: Any motion which repeats itself at regular intervals of time is called Periodic Motion or Harmonic Motion. Some of the examples of periodic motion are a rocking chair, a bouncing ball, a vibrating tuning fork, a swing in motion, the Earth in its orbit around the Sun, and a water wave.

•    The interval of time for a repetition, or cycle, of the motion is called a period.
•    The number of periods per unit time is called the frequency.

Thus, the period of the Earth’s orbit is one year, and its frequency is one orbit per year. A tuning fork might have a frequency of 1,000 cycles per second and a period of 1 millisecond (1 thousandth of a second).

Elasticity

Elasticity – The elasticity is the ability of a solid to return to its original shape or form after being subject to strain. Most solid materials display elasticity, up to a load point called the elastic limit; loads higher than this limit cause permanent deformation of the material.

Elastic Limit- The elastic limit is the maximum value of deforming force upto which a material displays elastic properties and above which a material losses its elastic properties.

Viscosity

Viscous Forces- These are forces which has tendency to oppose relative motion between different layers of liquid or gases.

Viscosity – Viscosity is the characteristic of a liquid due to which it opposes the relative motion between its various layers.

•    Viscosity is applicable to both liquid and gases.
•    The viscosity of a liquid is because of cohesive forces between layers.
•    Viscosity is liquid is less than viscosity of gases.
•    Solid has no viscosity.

Surface Tension

Cohesive Forces- Cohesive forces are the intermolecular forces, for example; hydrogen bonding and Van der Waals forces which cause a tendency in liquids to resist separation. These forces which are attractive forces exist between molecules of the same material. For example, rain falls as droplets, and not as fine mist, since water has strong cohesion hence its molecules pulls tightly together and droplets are formed. The cohesive force tends to bring closer molecules of a liquid, by making them comparatively large clusters which owes to molecules' dislike for its surrounding.

Floatation

Archimedes' Principle


•    The Archimedes' Principle is named after Archimedes of Syracuse
•    He discovered the law in 212 B.C.
•    The Archimedes' Principle states that any object, wholly or partially immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object.

Mathematically, the Archimedes' principle can be stated as Buoyancy = weight of displaced fluid.