Chapter 1 Physical World
Chapter 1 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 2017-18and 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.
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
It is the study of macroscopic phenomena. It includes subjects like
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.)
It deals with electric and magnetic phenomena associated with charged and magnetic bodies.
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.
It is the study of phenomenon connected with light and optical instruments like telescope, microscope etc.
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.)
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
Image source: NCERT textbooks
Link between technology and physics
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)
|Gravitational force||10–39 (Infinite)||All objects in the universe|
|Weak nuclear force||10–13 (Very short, Sub-nuclear size: ∼10–16m)||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.
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