Unit – IA

Physics and its Scope:

    • Science word is derived from latin word ‘Scientia’ which means ‘to know’. Science has many disciplines, Physics being one of them. The word Physics is derived from Greek word ‘Fusis’ meaning ‘nature’.
    • Physics is that branch of Science which deals with the study of matter and energy or matter or motion i.e. Physics is a study of matter and energy in its different forms. In other words, physics is the study of nature and its laws. All the different events taking place in nature always take place according to some basic rules and revealing these rules of nature from the observed events is physics.
    • As physics is a study of nature and its behaviour it is a real science. No one has been given authority to frame the rules for nature. Sir Issac Newton, Einstein are the great physicist because using the observations available at that time, they could guess and frame the laws of physics, which explain these events and the observations in a convincing way.
    • If a new phenomenon is observed which can not be explained using existing laws or rules we are always free to change the rules. Overlapping of physics with other branches of science gives rise to subjects like Biophysics, Biochemistry, Astrophysics, Geophysics etc.
    • The pre- 1900 study of physics is known as classical Physics, while the post-1900 study of physics is known as modern Physics. The classical physics includes the study of mechanics, gravitation, heat, sound, light, electricity and magnetism. The modern Physics includes the study of quantum mechanics, relativity, atoms, molecules, nuclei, elementary particles and condensed matter.

Scientific Methods:

  • The study of science and particularly in Physics is based on systematic observation, logical reasoning, model making and theoretical prediction. All the four steps taken together constitute what we call the ‘scientific method’.
  • The scientific method helps us to describe the given physical phenomenon or behaviour of a physical system in terms of a limited number of laws. This gives us what we call as ‘theory’.
  • Theory should be self-consistent and consistent with known experimental data. The discrepancy between the theory and experimental data had lead to new theories in Physics.

Relation Between Physics and Mathematics:

  • Physics is directly related to maths because the description of nature becomes easy if we have freedom to use mathematics.
  • In physics, we use mathematical techniques like algebra, trigonometry and calculus. Thus mathematics is a language of physics. Without knowledge of mathematics, it would be much more difficult to discover, understand and explain the laws of nature.

Different Branches of Physics:


  • Mechanics is a branch of physics, which deals with the motion of material bodies. In this branch, the forces responsible for the producing or changing the motion of the body are studied. The energy involved is also studied.
  • Newton’s laws of motion, the law of conservation of momentum and energy, Newton’s gravitation law forms the base of this branch of Physics.
  • Mechanics is further divided into statics, kinematics and dynamics.
  • Under this section, we are going to study topics like motion and its types, force, friction, viscosity, elasticity and surface tension.


  • Heat is the energy that a body possesses by virtue of the motion of the molecules of which it is composed of and the potential energy due to interatomic forces.
  • The term heat is also used to indicate the energy in the process of transfer between an object and its surroundings because a difference exists between their temperatures.
  • Thermodynamics is the name given to the branch of physics which studies the relationship between heat and mechanics.
  • Under this section, we are going to study heat transfer, expansion of solids, liquids and gases, gas laws, kinetic theory of gases, radiation.


  • Acoustic is a branch which studies sound. Wave motion is studied in this branch.
  • An object in a state of vibration can set medium particles in the vibration and this disturbance in the medium can travel from one point to another. Thus sound is wave motion itself.
  • Under this section, we are going to study wave motion, sound waves, simple harmonic progressive waves, stationary waves and their applications.


  • Optics is a branch of science which studies electromagnetic waves to which the eye responds (light).
  • Propagation of light means the propagation of electromagnetic waves with varying electric and magnetic fields through the vacuum or a transparent medium. It has two broad branches geometric optics and physical optics.
  • Under this section, we are going to study photometry, wave theory of light, dispersion, diffraction, interference of light

Electricity and Magnetism:

  • These topics are interrelated with each other. We have to take help of the other topic when we are studying one of them individually. Electricity deals with the forces on charged particles, the effect of such forces.
  • It also studies the phenomenon caused by the motion of charged particles. Magnetism can have effect the on electric current. magnetic materials can be used in producing electric currents. Electronics is a branch of electricity.

Modern Physics:

  • Modern physics is the branch of physics which deals with the recent developments in the science related with physics such as Radioactivity, X-Rays, Cathode Rays, Atomic and molecular Structure, Molecular structure, Quantum Theory and wave mechanics etc.