Physics and Fundamental Forces Class 11 Notes | EduRev

Physics Class 11

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JEE : Physics and Fundamental Forces Class 11 Notes | EduRev

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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 | EduRev

Fig: Newton's Reflector

2. 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 Modern Physics such as Special Relativity, Quantum Mechanics, etc.

Physics is the study of nature and its laws. Feynman has given a wonderful description of what is "understanding the nature". Suppose we do not know the rules of chess but are allowed to watch the moves of the players. If we watch the game for a long time, we may make out some of the rules. With the knowledge of these rules we may try to understand why a player played a particular move. However, this may be a very difficult task. Even if we know all the rules of chess, it is not so simple to understand all the complications of a game in a given situation and predict the correct move. Knowing the basic rules is, however, the minimum requirement if any progress is to be made.

One may guess at a wrong rule by partially watching the game. The experienced player may make use of a rule for the first time and the observer of the game may get surprised. Because of the new move some of the rules guessed at may prove to be wrong and the observer will frame new rules.

Physics goes the same way. The nature around us is like a big chess game played by Nature. The events in the nature are like the moves of the great game. We are allowed to watch the events of nature and guess at the basic rules according to which the events take place. We may come across new events which do not follow the rules guessed earlier and we may have to declare the old rules inapplicable or wrong and discover new rules.

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 | EduRev

Fig: This parabola-shaped lava flow illustrates the application of mathematics in physics—in this case, Galileo's law of falling bodies

5. 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.


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; Germany



 Theory of relativity

 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. 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 in 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 Rubbia, Simon Van der Meer 1984 Verified experimentally the predictions of the theory of electroweak force.


BRANCHES OF PHYSICS
(i) Classical Mechanics: Classical mechanics is a model of the physics of forces acting upon bodies. It is often referred to as "Newtonian mechanics" after Isaac Newton and his laws of motion. It deals with the motion of particles and general system of particles. Almost 95% of our pre-university syllabus in Class 11th and 12th falls under this branch of study.
(ii) Quantum Mechanics: Quantum mechanics is the branch of physics treating atomic and subatomic systems and their interaction based on the observation that all forms of energy are released in discrete units or bundles called "quanta". Remarkably, quantum theory typically permits only probable or statistical calculation of the observed features of subatomic particles. The study of this field is beyond the scope of our syllabus.
(iii) Relativistic Mechanics: The special theory of relativity enjoys a relationship with electromagnetism and mechanics; that is, the principle of relativity and the principle of stationary action in mechanics can be used to derive Maxwell's equations, and vice versa. Again, this field is way out of bounds for us to study at present.

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