1. Physics-Scope and excitements

Introduction : What is Science?

Science is a systematic understanding of natural phenomena in detail so that it can be predicted, controlled and modified. Science involves exploring, experimenting and speculating phenomena happening around us.

The word Science is derived from the Latin verb Scientia meaning ‘to know.

The scientific method is a way to gain knowledge in a systematic and in-depth way. It involves:

    • Systematic observation
    • Controlled experiments
    • Qualitative and Quantitative reasoning
    • Mathematical modeling
    • Prediction and verification (or falsification) of theories
    • Speculation or Prediction

Natural Sciences

Natural science is a branch of science concerned with the description, prediction, and understanding of natural phenomena, based on observational and empirical evidence. It consists of the following disciplines:

  • Physics
  • Chemistry
  • Biology

What is physics?

Physics is the study of nature and laws. There are so many different events in nature that are taking place and we expect that all these different events in nature are taking place according to some basic law and revealing these laws of nature from the observed events is Physics.

Humans have always been curious about the world around them. The night sky with its bright celestial objects has fascinated humans since time immemorial. The regular repetitions of the day and night, the annual cycle of seasons, the eclipse, the tides, the volcanoes, the rainbows, the color of the sky during sunrise and sunset have always been a source of wonder. All these phenomena are explained by the laws of Physics.

Word Physics has been originated from the Greek word phusikḗ which means nature.

There are two principal kinds of approaches in Physics which are listed below:

1. Unification: This is a method including all of the phenomena in the world in the form of a group of universal laws in various domains and conditions. The law of gravitation will be applied both on a falling apple from a tree and the movement of planets around the sun can be considered as examples. Every electric and magnetic phenomenon will be controlled by Electromagnetism laws.

2. Reduction: This is a method for deriving characteristics of complex systems from the properties and interaction of their constituent parts. We can take an example that the temperature studied under thermodynamics can be also connected to the average kinetic energy of molecules in a system (kinetic theory).

Role of Mathematics in Physics : 

 Description of all-natural phenomena is made simple by the help of mathematics. Thus we can say that mathematics is the language of Physics. With the help of Mathematics, we explain and understand the basic laws of physics in a better way.


Scope of Physics

Scope of Physics will be wide since it covers quantities with length magnitudes as big as 1040 m and more than that (astronomical studies of the universe) and as low as 10-14 m  or less (study of the electrons, protons etc). In the same way, the time scale is ranging from 10-22 to  1018 s and the mass is ranging from 10-30 kg to 1055 kg.

Physics can be categorized broadly into two kinds on the basis of its scope - Classical Physics and Modern Physics.

Basically, there are two domains of interest: macroscopic and microscopic. The macroscopic domain includes phenomena at the laboratory, terrestrial and astronomical scales. The microscopic domain includes atomic, molecular and nuclear phenomena.

Classical physics is a branch which is dealing with macroscopic phenomena while modern physics will be dealing with macroscopic phenomena.

Macroscopic Domain

The macroscopic domain includes phenomena at large scales like a laboratory, terrestrial and astronomical. It includes the following subjects:

1. Mechanics – It is based on Newton’s laws on motion and the laws of gravitation. It is concerned with the motion/equilibrium of particles, rigid and deformable bodies and the general system of particles.

Examples:  Propulsion of rocket by ejecting gases, Water/Sound waves, Equilibrium of bent rod under a load etc.

2. Electrodynamics – It deals with electric and magnetic phenomena associated with charged and magnetic bodies.

Examples:  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 phenomena involving light.

Examples,  Reflection and refraction of light, Dispersion of light through a prism, Colour exhibited by thin films etc.

4. Thermodynamics – It deals with systems in macroscopic equilibrium and changes in internal energy, temperature, entropy, etc. of systems under the application of external force or heat.

 Examples: Efficiency of heat engines, thermal expansion, Direction of physical and chemical process etc.

Microscopic domain

Microscopic Domain

The domain includes phenomena at minuscule scales like atomic, molecular and nuclear. It also deals with the interaction of probes like electrons, photons

and other elementary particles. Quantum theory has been developed to handle these phenomena.


Physics is exciting in many ways. To some people, the excitement comes from the elegance and universality of its basic theories, from the fact that a few basic concepts and laws can explain phenomena covering a large range of magnitude of physical quantities. To some others, the challenge in carrying out imaginative new experiments to unlock the secrets of nature, to verify or refute theories, is thrilling. Applied physics is equally demanding.

Factors responsible for the progress of Physics

  • Quantitative analysis along with qualitative analysis.
  • Application of universal laws in different contexts.
  • Approximation approach (complex phenomena broken down into a collection of basic laws).
  • Extracting and focusing on essential features of a phenomenon.

Hypothesis, Axiom and Models

A hypothesis is a supposition without assuming that it is true. It may not be proved but can be verified through a series of experiments.

Axiom is a self-evident truth that is accepted without controversy or question.

Model is a theory proposed to explain observed phenomena.

The assumption is the basis of physics, where a number of phenomena can be explained. These assumptions are made from experiments, observation and a lot of statistical data.

Physics-Technology and society

With the advancement of technology, human civilization also advanced.

For example, with technological advancement, steam engines are invented and then various industries are set up and an industrial revolution happens which in turn changed human civilization.

There is a complementing relationship between physics and technology. Sometimes physics gives rise to new technology and sometimes new technology gives rise to new physics.

For example, the advancement of the research of semiconductor materials which made it possible to make transistors, chips and integrated circuits which later contributed to the technological advancement of modern computers. In this example, Physics is giving rise to new technology.

Now with the advancement in technology of accelerators and detectors, it allows us to penetrate deeper in the atomic level and give rise to microphysics like nuclear physics, atomic physics, particle physics etc. In this example, the advancement in technology gave rise to new physics.

Technological Applications of Physics:

There are numerous examples in which Physics and its concepts paved the way to inventions as mentioned below.

  • The steam engine was invented during the industrial revolution in the eighteenth century.
  • Development of wireless communication after the discovery of the laws of electricity and magnetism.
  • Neuron-induced fission of uranium, attempted by Hahn and Meitner in 1938, showed the formation of nuclear power reactors and nuclear weapons.
  • Electricity has been produced from solar, wind, geothermal etc. energy.

Fundamental forces in Nature

Fundamental Forces in nature

The forces which we see in our day-to-day life like muscular, friction, forces due to compression and elongation of springs and strings, fluid and gas pressure, electric, magnetic, interatomic and intermolecular forces are derived forces as their originations are due to a few fundamental forces in nature.

A few fundamental forces are:

  1. Gravitational Force: It is the force of mutual attraction between any two objects by virtue of their masses. It is a universal force as every object experiences this force due to every other object in the universe.

  1. Electromagnetic Force: It is the force between charged particles. Charges at rest have electric attraction (between unlike charges) and repulsion (between like charges). Charges in motion produce magnetic force. Together they are called Electromagnetic Force.

  1. Strong Nuclear Force: It is the attractive force between protons and neutrons in a nucleus.It is charge-independent and acts equally between a proton and a proton, a neutron and a neutron, and a proton and a neutron. Recent discoveries show that protons and neutrons are built of elementary particles, quarks.

  1. Weak Nuclear Force: This 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 the neutrino. This particle was first predicted by Wolfgang Pauli in 1931.

Below table shows the difference between the above forces.

Conserved Quantities:

Physics has provided laws for summarising the investigations and observations of the phenomena happening in the universe.

  • Physical quantities will be held fixed with time and can be defined as conserved quantities. In the case of a body under external force, the kinetic and potential energy will be varying over time but the total mechanical energy (kinetic + potential) will be a constant.
  • Conserved quantities will be scalar (Energy) or vector (Total linear momentum and total angular momentum)

Conservation Laws:

A conservation law can be defined as a hypothesis on the basis of observation and experiments which is not able to be proven. These are verifiable through experiments.

Law of Conservation of Energy:

  • In accordance with the General Law of conservation of energy, the energies will be fixed over time and get transformed from one form to another.
  • The law of conservation of energy will be applied to the whole universe and it has been considered that the total energy of the universe is fixed.

Nature develops symmetric results at a different time under similar conditions.

Law of Conservation of Mass:

It can be defined as a principle that is usable in the analysis of chemical reactions.

  • Basically, a chemical reaction can be defined as a rearrangement of atoms among various molecules.
  • The difference will be formed as heat and the reaction is exothermic when the total binding energy of the reacting molecules will be less than the total binding energy of the product molecules.
  • The opposite will be correct for energy-absorbing reactions such as endothermic reactions.
  • As the atoms are not destroyed, only just rearranged, the summation of the mass of the reactants will be identified as the total mass of the products in a chemical reaction.
  • Mass will be in relation to energy through Einstein's theory,  E= mc2  where c will be the speed of light in vacuum.

Law of Conservation of Linear Momentum:

  • Law of conservation of linear momentum can be defined as the symmetry of laws of nature with respect to translation in space.
  • The law of gravitation is exactly identical on earth and moon even when the acceleration due to gravity on the moon is ⅙  than that on earth.

 Law of Conservation of Angular Momentum:

Isotropy of space means that no intrinsically preferred direction in space specifies the law of conservation of angular momentum.