Introduction to Physics


  • Science word is derived from Latin word ‘Scientia’ which means ‘to know’. Science has many disciplines, Physics being one of them. The word Physics is derived from Greek word ‘Fusis’ meaning ‘nature’. Physics is that branch of Science which deals with the study of matter and energy or matter or motion i.e. Physics is a study of matter and energy in its different forms. In other words, physics is the study of nature and its laws. We expect that all the different events taking place in nature always take place according to some basic rules and revealing these rules of nature from the observed events in physics.
  • As physics is a study of nature and its behaviour it is a real science. No one has been given authority to frame the rules. Sir Issac Newton, Einstein are the great physicist because using the observations available at that time, they could guess and frame the laws of physics, which explain these events and the observations in a convincing way. If a new phenomenon is observed which can not be explained using existing laws or rules we are always free to change the rules.
  • Knowledge of Physics overlaps with other sciences considerably, hence such overlapping gives rise to subjects like Biophysics, Biochemistry, Astrophysics, Geophysics etc.
  • Physics can be conveniently divided into two parts, classical Physics (Pre-1900) and modern Physics (Post – 1900). The classical physics includes the study of mechanics, gravitation, heat, sound, light, electricity and magnetism. The modern Physics includes the study of quantum mechanics, relativity, atoms, molecules, nuclei, elementary particles and condensed matter.

Scientific Methods:

  • The study of science and particularly in Physics is based on systematic observation, logical reasoning, model making and theoretical prediction and necessary modifications. All the four steps taken together constitute what we call the ‘scientific method’. The scientific method helps us to describe the given physical phenomenon or behaviour of a physical system in terms of a limited number of laws. This gives us what we call as ‘theory’. Theory should be self-consistent and consistent with known experimental data. The discrepancy between the theory and experimental data has to lead to new theories in Physics.

Relation Between Physics and Mathematics:

  • Physics is directly related to maths because the description of nature becomes easy if we have the freedom to use mathematics.
  • In physics, we use mathematical techniques like algebra, trigonometry and calculus. Thus mathematics is a language of physics. Without knowledge of mathematics, it would be much more difficult to discover, understand and explain the laws of nature.
  • But we should note that mathematics itself is not a physics. To understand nature is a journey of physics, mathematics is the mean of the journey.

Different Branches of Physics:


  • Mechanics is a branch of physics, which deals with the motion of material bodies. In this branch, the forces responsible for the producing or changing the motion of the body are studied. The energy involved is also studied. Newton’s laws of motion, the law of conservation of momentum and energy, Newton’s gravitation law forms the base of this branch of Physics.


  • Heat is the energy that a body possesses by virtue of the motion of the molecules of which it is composed of and the potential energy due to interatomic forces. The term heat is also used to indicate the energy in the process of transfer between an object and its surroundings because a difference exists between their temperatures. Thermodynamics is the name given to the branch of physics which studies the relationship between heat and mechanics.


  • Acoustic is a branch which studies sound. Wave motion is studied in this branch.  An object in a state of vibration can set medium particles in the vibration and this disturbance in the medium can travel from one point to another. Thus sound is wave motion itself.


  • Optics is a branch of science which studies electromagnetic waves to which the eye responds (light). Propagation of light means the propagation of electromagnetic waves with varying electric and magnetic fields through a vacuum or a transparent medium. It has two broad branches geometric optics and physical optics.

Electricity and Magnetism:

  • These topics are interrelated with each other. We have to take help of another topic when we are studying one of them individually. Electricity deals with the forces on charged particles, the effect of such forces. It also studies the phenomenon caused by the motion of charged particles. Magnetism can have an effect on the electric current. magnetic materials can be used in producing electric currents. Electronics is the branch of electricity.

Modern Physics:

  • Modern physics is the branch of physics which deals with the recent developments in the science related with physics such as Radioactivity, X-Rays, Cathode Rays, Atomic and Molecular Structure, Quantum Theory and wave mechanics etc.

Pioneers of Physics

Name of Scientist Country Field / Discovery/Invention
Ampere, Andre Marie

(1775- 1836)

France Current Electricity


(287- 212 B.C.)

Greece Archimedes principle
Avogadro, Amedeo

(1776 – 1856)

Italy Avogadro’s law, Gaseous state
Bardeen J. United States Transistor
Benjamin Franklin


United States Lightning conductor

Becquerel Henry Antoine


France Natural radioactivity
Bernouilli, Daniel

(1700 – 82)

Sweden Bernoulli’s principle, working of an aeroplane

Bohr, Niels Henrik David

(1885 – 1962)

Denmark Bohr’s theory of hydrogen atom
Born, Max

(1882 – 1970)

England Quantum mechanics

Boyle, Robert

(1627- 1691)

Ireland Study of gaseous state, Boyle’s law
Bethe A. H.


Germany / France Theory of nuclear reaction

A. Vatta


Italy Electric Battery
Jacques Alexander Cesar

(1746 – 1823)

England Study of gaseous state, Charle’s law

Clerk-Maxwell, James

(1831 – 79)

England Electromagnetic radiations
Compton A. H.


United States Compton effect of light

Copernicus Nicolas

(1473 – 1543)

Poland Earth revolves around the sun
Curie, Pierre (1859-1906)

& Marie (1867-1934)

Poland Radioactivity, Radium , Polonium

David Edward Hughes


England / USA Microphone
de Broglie France Wave nature of the electron

Dennis Papin


France Pressure cooker
Dennis Gabor


 Hungary Holography
Edison Thomas Alva United States Thermionic emission
Einstein Albert



Germany Special theory of relativity, Electromagnetic theory of light. Photoelectric effect.

Elisha Otis


United States Passenger lift


Italy Barometer



France Internal combustion engine
Enrico Fermi


Italy/ United States Demonstration of the existence of new radioactive elements.



France Refrigerator
Faraday, Michael


England Laws of electrolysis, electromagnetic induction, dynamo

Galileo Galilei


Italy Laws inertia, simple pendulum, Telescope,                Law of falling bodies.
Goldstein E. England Proton

Graham Bell


Scotland Telephone


Germany Mercury thermometer



Italy Wireless


Germany Electromagnetic waves

Hans Lippershey


Netherlands Telescope.
Hess Victor Franz Austria Cosmic rays

Hooke, Robert


England Elasticity, Hooke’s law
K. Onnes


Holland Properties of matter at low temperatures

Huygens, Christiaan


Holland Wave theory of light
James Chadwick


England Neutron

James Dewar


Scotland Vacuum flask
James Watt


Scotland Condensing steam engine

John Baird


Scotland Television
John Fleming


England Diode

John Napier


Scotland Logarithms
V. Sauerbronn


Germany Bicycle

Kepler, Johann


Germany motion of astronomical bodies, Keppler’s law (Planetary Motion)
Lee De Forest


United States Triode
Lawrence E.O. America cyclotron
Maxwell Scotland Electromagnetic theory
Marconi G. Italy Wireless telegraphy
Millikan R. A. United States Atomicity of charge, Charge on electron

Newton Issac


England Calculus, Laws of motion and gravity
Oersted H. C.


Denmark Electromagnetism

Oppenheimer, J. Robert


America Nuclear explosion
Pauli Wolfgang Austria Quantum exclusion principle

Planck, Max


Germany Quantum theory
Raman C.V. India Scattering of light by molecules

Robert H. Goddard


United States Liquid fuel rocket
Roentgen (Röntgen), Wilhelm Conrad


Germany X-Rays

Rudolph Diesel


Germany Diesel engine
Rutherford Ernest


England Radioactivity, the structure of an atom
Thomson J. J. England electrons, Cathode rays
Thomas Newcomen


England Steam Engine

Wilbur Orville Wright


United States Aeroplane
William Stanley


United States Electric transformer

William Sturgeon


England Electromagnet
Werner Heisenberg


German Quantum mechanics
Yukawa Hideki Japan Theory of nuclear forces
Presper Eckert and John W. Mauchly


United States Electronic computer

John Bardeen, W. Brattain, W. Shockley


United States Transistor
Theodore Mainmann


United States Laser

Important scientific Principles:

Technology / Instrument/ Machine                      Principle
Steam Engine Thermodynamics
Aeroplane Bernoulli’s principle
Rocket Propulsion Newton’s second and third law
Hydroelectric Power Principle of conservation of energy
Heat Engines Laws of Thermodynamics
Refrigerator Laws of Thermodynamics
Electric Generator Electromagnetic induction
Radio Electromagnetic waves
Television Electromagnetic waves
Cyclotron Simultaneous application of magnetic and electric field
Nuclear Reactor Nuclear Fission
LASER Population inversion
Calculators Digital logic of electronic circuit
Computers Digital logic of electronic circuit
Atom Bomb Nuclear Fission
Hydrogen Bomb Nuclear Fusion
Genetic Engineering Role of DNA in heredity
Production of ultra-high magnetic field Superconductivity





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