Physics and Fundamental Forces Class 11 Notes | EduRev

Physics Class 11

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PHYSICAL WORLD
1. Science 
Science is a systematic and organised attempt to acquire knowledge about the surroundings through observations, experiments and verification.

Physics and Fundamental Forces Class 11 Notes | EduRevFig: Newton's Reflector2. Scientific Method
Several interrelated steps are involved in the scientific method. Some of the most significant steps are as follows:

• The systematic observations
• Reasoning
• Mathematical modelling
• Theoretical prediction


3. Physics
Physics is a fundamental science concerned with understanding the natural phenomena that occur in our universe. It has many branches such as Mechanics, Electromagnetism, Thermodynamics, Modern Physics, etc.
Between 1600 and 1900, three broad areas were developed, which is together called Classical Physics. These three areas of study are classical mechanics, thermodynamics and electromagnetism. But by 1905 it became apparent that classical ideas failed to explain several phenomena. Then some new theories were developed in what is called Modem Physics such as Special Relativity, Quantum Mechanics, etc.

4. Scope and Excitement of Physics

  • The scope of Physics is very broad and covers a wide range of magnitude of physical quantities such as length, mass, time, energy, etc.
  • It deals with the macroscopic worlds like galaxies and the universe as well as microscopic world like the nucleus of an atom and fundamental particles like electrons, protons, neutrons etc.
  • Immense excitement is involved in the study of physics since it explains every naturally occurring phenomenon with a set of rules, so that clear understanding can be achieved. The challenge to carry out imaginative new experiments to unlock the secrets of nature, to verify or refute theories, is really exciting.

Physics and Fundamental Forces Class 11 Notes | EduRevFig: This parabola-shaped lava flow illustrates the application of mathematics in physics—in this case, Galileo's law of falling bodies5. Physics in Relation to Other Sciences
Physics is a very significant branch of science which plays a crucial role in understanding the developments pertaining to the other branches of science such as Chemistry, Biology etc.

(i) Physics in relation to Mathematics: Study of physical variables led to the idea of differentiation, integration and differential equation. Meaningful interpretation of Mathematics becomes Physics.

(ii) Physics in relation to Chemistry: The concept of X-ray diffraction and radioactivity has helped to distinguish between the various solids and to modify the periodic table.
Understanding the bonding and the chemical structure of substances is easy with the help of the concept of interactions between various particles.

(iii) Physics in relation to Astronomy: Optical telescopes of reflecting and refracting type enabled man to explore the space around. Discoveries like radio telescopes have revolutionized the study of Astronomy.

(iv) Physics in relation to Biology: The conceptual study of pressure and its measurement has helped us to know blood pressure and hence the functioning of the heart. The invention of X-rays developed the field of diagnosis. Electron and optical microscopic designs have revolutionized the study of medical science.

(v) Physics in relation to Meteorology: The discoveries regarding the study of pressure variations help us to forecast the weather.
Various other inventions of physics have opened new vistas of study in the field of sciences and social sciences.

6. Physics in Relation to Technology and Society:
Advancement in physics has led to new technologies and vice-versa. Sometimes technology gives rise to a new dimension of physics; at other times physics generates new technology.
In fact, technological development is closely related to the application of science and physics in particular. Physics has a dominant influence on society. It has helped the human beings to develop their ideas. Development of digital communication systems, rapid mass transport system, lasers making bloodless surgeries, etc., has made human life easy and pleasant.
There are four fundamental forces in nature that govern the diverse phenomena of the microscopic and macroscopic world. These are :

(i) Gravitational force

(ii) Electromagnetic force 

(iii) Strong nuclear force

(iv) Weak nuclear forcePhysics and Fundamental Forces Class 11 Notes | EduRevFig: Gravitational Force between 2 objects

  • Unification of forces is a basic quest in physics. The electromagnetic and the weak nuclear forces have now been unified and are seen as aspects of a single ‘electro-weak’ force. Attempts are being made to unify electro-weak and the strong force.
  • Conservation of energy-momentum angular momentum charge etc. are considered to be the fundamental laws in physics. Conservation laws have a deep connection with the symmetries of nature. Symmetries of space and time and other types of symmetries play a central role in modern theories of fundamental forces in nature.

IMPORTANT TABLES
Table 1.1 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

The 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 Skłodowska 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 the atom

New Zealand

Niels Bohr

Quantum model of the hydrogen atom

Denmark

C.V. Raman

Inelastic scattering of light by molecules

India

Louis Victor de Broglie

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

India

John Bardeen

Transistors; Theory of superconductivity

U.S.A

C.H. Townes

Maser; Laser

U.S.A

Abdus Salam

Unification of weak and electromagnetic interactions

Pakistan


Table 1.2. Progress in the unification of different forces/domains in nature:

Technology

Scientific principles

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

Hydroelectric power

Conversion of gravitational potential energy into electrical energy

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 (Tokamalt)

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.

 

Table 1.3. Fundamental forces of 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 (~ 10-16 m)

Some elementary particles, particularly electron and neutrino

Electromagnetic force

10-2

Infinite

Charged particles

Strong nuclear force

1

Short, nuclear

size (~10-m)                           

Nucleons, heavier elementary particles


Table 1.4. The link between technology and physics:

Name of the physicist

Year

Achievement in unification

Isaac Newton

1687

Unified celestial and terrestrial mechanics; showed that the same laws of motion and the law of gravitation apply to both the domains.

Hans Christian Oersted Michael Faraday

1820

1830

Showed that electric and magnetic phenomena are inseparable aspects of a unified domain: electromagnetism.

James Clerk Maxwell

1873

Unified electricity, magnetism and optics; showed that light is tin electromagnetic wave.

Sheldon Glashow, Abdus Salam, Steven Weinberg

1979

Showed that the 'weak' nuclear force and the electro­magnetic force could be viewed as different aspects of a single electro-weak force.

Carlo Rubia, Simon

Vander Meer

1984

Verified experimentally the predictions of the theory of electro-weak force. 


7. 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. These conservation laws have a deep connection with symmetries of nature. 
  • Symmetries of space and time, and other types of symmetries play a central role in modern theories of fundamental forces in nature.

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