Physical world:

• Human beings have always been curious to interact with nature to know about different phenomenon associated with the physical world.
• The inquiring and imaginative human mind has responded to the wonder and awe of nature in different ways.
• This led to development of modern science and technology.

Science:

• The word Science originates from Latin verb ‘Scientia’ which means ‘to know’. In Sanskrit, it is ‘vijnan’ and in Arabic, it is ‘Ilm’.
• 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 associated with the physical world.
• The role of science is to unravel the secrets of nature via systematic observations, controlled experiments, qualitative and quantitative reasoning, mathematical modelling, prediction and verification or falsification of theories.

Physics:

• Physics is a basic discipline in the category of Natural Sciences.
• It is a branch of science which deals with the study of the basic laws of nature and their manifestation in different natural phenomena.
• We can also say that physics is the study of matter, energy, and the interaction between them.
• A few concepts and laws are used to explain diverse physical phenomena in the physical world.

The two principal thrusts of physics are:

1. Unification: The act of unifying the different laws associated with nature valid for different phenomena into a single theory that explains all the different phenomena is said to be unification.
2. Reduction: The procedure or theory that reduces complex data and phenomena to simple terms are said to be reduction. It is regarded as the “heart of physics”.

Domains of interest in physics:

There are mainly two domains of interest in physics to study the physical world:

1. Macroscopic: It includes phenomena at the laboratory, terrestrial and astronomical scales. Mechanics, Electrodynamics, Optics and Thermodynamics are included in macroscopic phenomena and classical physics deals it.
2. Microscopic: It includes atomic, molecular and nuclear phenomena. 

Classical physics:

• It involves the study of macroscopic phenomena. It has a wide range of evaluation. Several branches of physics are dealt with it.
• Some of the branches which we study in classical physics are Mechanics, Electrodynamics, Optics and Thermodynamics.

1. Mechanics:

• The branch of physics that deals with the motion of material objects are said to be mechanics.
• Newton’s law of motion, gravitation and like study of materials are studied in mechanics.

2. Electrodynamics:

• It deals with electric and magnetic phenomena.
• Electrodynamics includes the problems of the motion of a current-carrying conductor in a magnetic field, the response of a circuit to an AC voltage (signal), the propagation of radio waves in the ionosphere, etc.

3. Optics:

• It deals with the study of light and its phenomenon.
• Optics deals with the working of telescopes and microscopes, colours exhibited by thin films, working of camera etc.

4. 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 problems related to transfer of heat is dealt with in thermodynamics.

Quantum Physics:

• In this branch, we study the subatomic particle and the nature associated with it.
• Classical physics fails to explain the microscopic phenomena, then it comes to dealing in quantum physics.

Physics, Technology and Society:

• All the three terms are associated with each other uniformly.
• Sometimes technology gives rise to new physics; at other times physics generates new technology.
• If either is generated it affects the civilization thus the society as all the three are the crucial part of the physical world.

Fundamental forces in nature:

All the force present in nature can be categorized into 4 types of fundamental forces, they are:

1. Gravitational Force:

• It is the universal force.
• The force of mutual attraction between any two objects by virtue of their masses is said to be gravitational force.
• Every single object on this earth experience gravity.
• Gravity has also a key role in motion of the moon and artificial satellites around the earth, motion of the earth and planets around the sun and the motion of bodies falling to the earth.

2. Electromagnetic Force:

• It is the force between charged particles.
• Moving charge produces magnetic field around it and vice versa, so we call it electromagnetic force.
• It is a strong force also it acts over large distances and does not need any intervening medium.
• It is electromagnetic force which decides the structure of atoms and molecules.
• Electromagnetic force can be attractive or repulsive on the other hand gravitational force is only attractive.

3. Strong Nuclear force:

• Protons and neutrons are bound together in the nucleus with the help of strong nuclear force.
• The nuclear force is about 100 times the electromagnetic force in strength so the strong nuclear force is the strongest of all fundamental forces.
• This force is responsible for the stability of nuclei.

4. Weak nuclear force:

• The range of weak nuclear force is of the order of 10^-16
• It is weaker than electromagnetic force and strong nuclear force but is little stronger than gravitational force.

Conservation Laws in Physics:

• Conserved quantities are the physical quantities that remain unchanged in a process.
• There are some conservation laws associated with nature. They are:
  Law of conservation of Energy, Mass, Linear momentum, Charge, Angular momentum, Parity, etc.
• These conservation laws play an important role in studying different forces of nature and the physical world.

To practice Question /Answer of this chapter please click here  Q/A on Physical World