Physics - Meaning
The term derived from Greek word meaning nature. Sanskrit equivalent of the word Physics is Bhautiki that is used to refer to the study of the physical world.
In a broader sense Physics is the study of the basic laws of nature and their manifestation. Physics is all about explaining diverse physical phenomena with the help of few concepts and laws.
In a broader sense Physics is the study of the basic laws of nature and their manifestation. Physics is all about explaining diverse physical phenomena with the help of few concepts and laws.
Scope and Excitement of Physics
In Physics, there are two domains of interest macroscopic and microscopic.
Macroscopic domain It includes phenomena at the laboratory, terrestrial and astronomical scales.
Microscopic domain It includes atomic, molecular and nuclear phenomena.
However, recently a third domain of interest between macroscopic domain and microscopic domain (Mesoscopic) has also come in light. In this domain scientists deals with a few tens or hundreds of atoms, has emerged as an exciting field of research.
Various theories related to macroscopic domain and microscopic domain are further categorized as:
Macroscopic domain It includes phenomena at the laboratory, terrestrial and astronomical scales.
Microscopic domain It includes atomic, molecular and nuclear phenomena.
However, recently a third domain of interest between macroscopic domain and microscopic domain (Mesoscopic) has also come in light. In this domain scientists deals with a few tens or hundreds of atoms, has emerged as an exciting field of research.
Various theories related to macroscopic domain and microscopic domain are further categorized as:
Classical Physics
It is the study of macroscopic phenomena. It includes subjects as
Mechanics Under mechanics, we study:
i. Newton’s laws of motion
ii. The law of gravitation is concerned with the motion (or equilibrium) of particles, rigid and deformable bodies, and general systems of particles.)
Electrodynamics It deals with electric and magnetic phenomena associated with charged and magnetic bodies.
Thermodynamics It deals with systems in macroscopic equilibrium and is concerned with changes in internal energy, temperature, entropy, etc. of the system through external work and transfer of heat, the efficiency of heat engines and refrigerators etc.
OpticsIt is the study of phenomenon connected with light and optical instruments like telescope, microscope etc.
Mechanics Under mechanics, we study:
i. Newton’s laws of motion
ii. The law of gravitation is concerned with the motion (or equilibrium) of particles, rigid and deformable bodies, and general systems of particles.)
Electrodynamics It deals with electric and magnetic phenomena associated with charged and magnetic bodies.
Thermodynamics It deals with systems in macroscopic equilibrium and is concerned with changes in internal energy, temperature, entropy, etc. of the system through external work and transfer of heat, the efficiency of heat engines and refrigerators etc.
OpticsIt is the study of phenomenon connected with light and optical instruments like telescope, microscope etc.
Quantum Theory
It is the framework for explaining microscopic phenomena as classical physics can’t explain phenomenon at microscopic level (or smaller dimensions like atoms, nuclei etc.)
Physics, Technology and Society
There are number of examples in the world which shows close relation between physics, technology and society. Such as, the steam engine is inseparable from the Industrial Revolution in England in the 18th century, which had great impact on the course of human civilization. Wireless communication technology, computers are some other examples.
Some physicists from different countries of the world and their major contributions
| Name | Major Contribution /Discovery |
Country of Origin |
|---|---|---|
| Archimedes | Principle of buoyancy; Principle of the lever | Greece |
| Galileo Galilei | Law of inertia | Italy |
| Christiaan Huygens | Wave theory of light | Holland |
| Isaac Newton | Universal law of gravitation; Laws of motion;Reflecting telescope | U.K. |
| Michael Faraday | Laws of electromagnetic induction | U.K. |
| James Clerk Maxwell | Electromagnetic theory; Light-an electromagnetic wave | U.K. |
| Heinrich Rudolf Hertz | Generation of electromagnetic waves | Germany |
| J.C. Bose | Ultra short radio waves | India |
| W.K. Roentgen | X-rays | Germany |
| J.J. Thomson | Electron | U.K. |
| Marie Sklodowska Curie | Discovery of radium and polonium; Studies on natural radioactivity | Poland |
| Albert Einstein | Explanation of photoelectric effect; Theory of relativity | Germany |
| Victor Francis Hess | Cosmic radiation | Austria |
| R.A. Millikan | Measurement of electronic charge | U.S.A. |
| Ernest Rutherford | Nuclear model of atom | New Zealand |
| Niels Bohr | Quantum model of hydrogen atom | Denmark |
| C.V. Raman | Inelastic scattering of light by molecules | India |
| Louis Victor de Borglie | Wave nature of matter | France |
| M.N. Saha | Thermal ionisation | India |
| S.N. Bose | Quantum statistics | India |
| Wolfgang Pauli | Exclusion principle | Austria |
| Enrico Fermi | Controlled nuclear fission | Italy |
| Werner Heisenberg | Quantum mechanics; Uncertainty principle | Germany |
| Paul Dirac | Relativistic theory of electron; Quantum statistics | U.K. |
| Edwin Hubble | Expanding universe | U.S.A. |
| Ernest Orlando Lawrence | Cyclotron | U.S.A. |
| James Chadwick | Neutron | U.K. |
| Hideki Yukawa | Theory of nuclear forces | Japan |
| Homi Jehangir Bhabha | Cascade process of cosmic radiation | India |
| Lev Davidovich Landau | Theory of condensed matter; Liquid helium | Russia |
| S. Chandrasekhar | Chandrasekhar limit, structure and evolution of stars | Russia |
| John Bardeen | Transistors; Theory of super conductivity | U.S.A. |
| C.H. Townes | Maser; Laser | U.S.A. |
| Abdus Salam | Unification of weak and electromagnetic interactions | Pakistan |
Link between technology and physics
| Technology | Scientific principle(s) |
|---|---|
| Steam engine | Laws of thermodynamics |
| Nuclear reactor | Controlled nuclear fission |
| Radio and Television | Generation, propagation and detection of electromagnetic waves |
| Computers | Digital logic |
| Lasers | Light amplification by stimulated emission of radiation |
| Production of ultra high magnetic fields | Superconductivity |
| Rocket propulsion | Newton’s laws of motion |
| Electric generator | Faraday’s laws of electromagnetic induction |
| Aeroplane | Bernoulli’s principle in fluid dynamics |
| Particle accelerators | Motion of charged particles in electromagnetic fields |
| Sonar | Reflection of ultrasonic waves |
| Optical fibres | Total internal reflection of light |
| Non-reflecting coatings | Thin film optical interference |
| Electron microscope | Wave nature of electrons |
| Photocell | Photoelectric effect |
| Fusion test reactor (Tokamak) | Magnetic confinement of plasma |
| Giant Metrewave Radio Telescope (GMRT) | Detection of cosmic radio waves |
| Bose-Einstein condensate | Trapping and cooling of atoms by laser beams and magnetic fields. |
Fundamental Forces in Nature
Four fundamental forces in nature that govern the diverse phenomena of the macroscopic and the microscopic world are given below
a)Gravitational Force
b)Electromagnetic Force
c)Strong Nuclear Force
d)Weak Nuclear Force
a)Gravitational Force
b)Electromagnetic Force
c)Strong Nuclear Force
d)Weak Nuclear Force
Basic Properties of Fundamental Forces in Nature
| Name | Relative Strength (& Range) | Operates among |
|---|---|---|
| Gravitational force | 10-39(Infinite) | All objects in the universe |
| Weak nuclear force | 10-13(Very short, Sub-nuclear size: ∼10–16m) | Some elementary particles, particularly electron and neutrino |
| Electromagnetic force | 10-2 (Infinite) | Charged particles |
| Strong nuclear force | 1 (Short, nuclear size 10-15m | Nucleons, heavier elementary particles |
Conservation Laws in Physics
The physical quantities that remain unchanged in a process are called conserved quantities. Some of the general conservation laws in nature include the laws of conservation of energy, mass, linear momentum, angular momentum, charge, parity, etc. Some conservation laws are true for one fundamental force but not for the other
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