CBSE Class 11 Physics Notes: Physical World

Sep 8, 2017 17:50 IST

Class 11 Physics Notes: Physical World
Class 11 Physics Notes: Physical World

Class 11 Physics chapter wise notes based on Chapter 1, Physical World of 11th Physics NCERT textbook are available here. These notes are as per latest CBSE Class 11 Physics Syllabus 2017-18 and important for CBSE school exams and completive examinations like NEET, JEE Mains etc.

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.

CBSE Class 11 Physics Syllabus 2017 - 2018

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 categorised as given below

Classical Physics

It is the study of macroscopic phenomena. It includes subjects like

• Mechanics:

Under mechanics, we study

Newton’s laws of motion

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.

• Optics:

It 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.)

Physical World: CBSE Class 11 NCERT Solution

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 civilisation. Wireless communication technology, computers are some other examples.

Some physicists from different countries of the world and their major contributions

Some physicists from different countries of the world and their major contributions

Image source: NCERT textbooks

Link between technology and physics

Some physicists from different countries of the world and their major contributions

Image source: NCERT textbooks

Fundamental Forces in Nature

Four fundamental forces in nature that govern the diverse phenomena of the macroscopic and the microscopic world are given below

• Gravitational Force

• Electromagnetic Force

• Strong Nuclear Force

• Weak Nuclear Force

Basic Properties of Fundamental Forces in Nature


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 ∼10–15 m)

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.

You will study details of these laws in consecutive chapters.

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.

NCERT Exemplar Questions: CBSE Class 11 Physics – Chapter 1

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