NCERT Notes For Class 11 Physics Chapter 1 Physical World

Class 11 Physics Chapter 1 Physical World

NCERT Notes For Class 11 Physics Chapter 1 Physical World, (Physics) exam are Students are taught thru NCERT books in some of state board and CBSE Schools.  As the chapter involves an end, there is an exercise provided to assist students prepare for evaluation.  Students need to clear up those exercises very well because the questions withinside the very last asked from those. 

Sometimes, students get stuck withinside the exercises and are not able to clear up all of the questions.  To assist students solve all of the questions and maintain their studies with out a doubt, we have provided step by step NCERT Notes for the students for all classes.  These answers will similarly help students in scoring better marks with the assist of properly illustrated Notes as a way to similarly assist the students and answering the questions right.

NCERT Notes For Class 11 Physics Chapter 1 Physical World

Class 11 Physics Chapter 1 Physical World



  • The word Science originates from the Latin verb Scientia meaning ‘to know’
  • Science is a systematic attempt to understand natural phenomena in as much detail and depth as possible, and use the knowledge so gained to predict, modify and control phenomena.


  • Systematic observations
  • controlled experiments
  • qualitative and quantitative reasoning
  • mathematical modeling
  • Prediction and verification or falsification of theories.


  • Physics is a basic discipline in the category of Natural Sciences
  • Physics as a study of the basic laws of nature and their manifestation in different natural phenomena
  • In Physics, we attempt to explain diverse physical phenomena in terms of a few concepts and laws.
  • The two approaches of physics are unification and reductionism.
  • Attempting to explain diverse physical phenomena with a few concepts and laws is unification.
  • An attempt to explain a macroscopic system in terms of its microscopic constituents is reductionism.


Macroscopic domain

  • The macroscopic domain includes phenomena at the laboratory, terrestrial and astronomical scales.
  • Classical Physics deals mainly with macroscopic phenomena and includes subjects like Mechanics, Electrodynamics, Optics and Thermodynamics.
  • Mechanics -founded on Newton’s laws of motion
  • Electrodynamics – deals with electric and magnetic phenomena associated with charged and magnetic bodies.
  • Optics – deals with the phenomena involving light
  • 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.

Microscopic domain

  • The microscopic domain includes atomic, molecular and nuclear phenomena.
  • Quantum Theory is currently accepted as the proper framework for explaining microscopic phenomena.

Link between technology and physics


Scientific principle

Steam engine

Laws of thermodynamics

Nuclear reactor

Controlled nuclear fission

Radio and TV

Generation, propagation and detection of electromagnetic waves


Digital logic


Light amplification by stimulated emission of radiation

Production of ultrahigh magnetic fields


Rocket propulsion

Newton’s laws of motion

Electric generator

Faraday’s laws of electromagnetic induction

hydroelectric power

Conversion of gravitational potential energy in to electrical energy


Bernoulli’s principle in fluid dynamics

Particle accelerators

Motion of charged particles in electromagnetic fields


Reflection of ultrasonic waves

Optical fibres

Total internal reflection of light

Electron microscope

Wave nature of electrons


Photoelectric effect



  • Gravitational force
  • Electromagnetic force
  • Strong nuclear force
  • Weak Nuclear force

Gravitational force

  • Force of mutual attraction between two weak bodies due to their masses.
  • It is a universal force.
  • It is a non-contact force.
  • Obeys inverse square law.
  • Weakest force of all forces.
  • Long range force.
  • Independent of intervening medium.

Electromagnetic force

  • The force between charged particles.
  • May be repulsive or attractive.
  • Depends on the intervening medium.
  • Large compared to gravitational force.
  • Acts over large distances.
  • Electric force between two protons, for example, is 1036 times the gravitational force between them, for any fixed distance.
  • The forces like ‘tension’, ‘friction’, ‘normal force’, ‘spring force’, etc. are electromagnetic.

Strong nuclear force

  • The strong nuclear force binds protons and neutrons in a nucleus.
  • Attractive in nature.
  • Strongest force in nature-about 100 times the electromagnetic force in strength.
  • It is charge-independent and acts equally between a proton and a proton, a neutron and a neutron, and a proton and a neutron.
  • Short range force-about nuclear dimensions.

Weak nuclear force

  • Appears only in certain nuclear processes such as the β-decay of a nucleus.
  • In β-decay, the nucleus emits an electron and an uncharged particle called neutrino.
  • The electron and neutrino interacts through weak force.
  • not as weak as the gravitational force, but much weaker than the strong nuclear and electromagnetic forces.
  • The range of weak nuclear force is exceedingly small, of the order of 10-16m.

Ratio of strengths of forces

Strong force > electromagnetic > force > gravitational

The ratio of strengths is 1: 10-2: 10-13: 10-39

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