7. Science :--- The word science comes from a Latin word “scientia” which means
‘to know’.
Science is nothing but the knowledge gained through the systematic
observations and experiments.
Science means organized knowledge.
Albert Einstein called Galileo the “father of modern science.”
Jagdish Chandra Bose, Father Of Modern Science In India.
Natural Sciences can be broadly divided in three branches namely Physics,
Chemistry and biology.
Scientific Method ----are used to observe things and natural phenomena.
• Observations
• Controlled experiments,
• Qualitative and quantitative reasoning,
• Mathematical modeling,
• Prediction and
• Verification or falsification of theories
8. Physics :--- The word physics has its origin in a Greek word fusis meaning ‘nature’.
Physics is a quantitative science, where we measure various physical
quantities during experiments.
Sanskrit equivalent of the word Physics is Bhautiki that is used to refer to the study of the physical
world
Physics is the most basic science, which deals with the study of nature and
natural phenomena.
Physics is an empirical study.
Physics is the study of physical world and matter and its motion through space
and time, along with related concepts such as energy and force.
“Physics is the king of all sciences as it helps us understand the way nature
works. It is at the centre of science.
Principal thrusts in Physics
• There are two principal thrusts in Physics
• 1.Unification 2. reduction
9. Two principal types of approaches in Physics are:
1. Unification: This approach considers all of the world’s phenomena as a
collection of universal laws in different domains and conditions.
Example, law of gravitation applies both to a falling apple from a tree as well as
motion of planets around the sun.
Electromagnetism laws govern all electric and magnetic phenomena.
2. Reduction:--- This approach is to derive properties of complex systems from the
properties and interaction of its constituent parts.
Example, temperature studied under thermodynamics is also related to average kinetic energy
of molecules in a system (kinetic theory).
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.
Mesoscopic domain:--- However, recently a third domain of interest between macroscopic
domain and microscopic domain (Mesoscopic) has also come in light.
10. In this domain scientists deals with a few tens or hundreds of atoms, has emerged as an exciting
field of research.
Macroscopic Domain ----Macroscopic domain includes phenomena at large scales
like laboratory, terrestrial and astronomical.
It includes following subjects:
1. Mechanics – It is based on Newton’s laws on motion and the laws of
gravitation. It is concerned with motion/equilibrium of particles, rigid and
deformable bodies and general system of particles.
Examples, a. Propulsion of rocket by ejecting gases
b. Water/Sound waves
2. Electrodynamics – It deals with electric and magnetic phenomena associated
with charged and magnetic bodies.
Examples, a. motion of a current-carrying conductor in a magnetic field
3. Optics – It deals with phenomena involving light.
Examples, a. Reflection and refraction of light
b. Dispersion of light through a prism
11. 4. Thermodynamics – It deals with systems in macroscopic equilibrium and
changes in internal energy, temperature, entropy etc. of systems under
application of external force or heat.
Examples, a. Efficiency of heat engines
b. Direction of physical and chemical process
Microscopic Domain------- Microscopic domain includes phenomena at minuscule
scales like atomic, molecular and nuclear.
It also deals with interaction of probes like electrons, photons and other
elementary particles. Quantum theory has been developed to handle these
phenomena.
Modern Physics Refers to the concepts in physics that have surfaced since the
beginning of the 20th century.
1. Quantum mechanics-- The study of the discrete nature of phenomena at the
atomic and subatomic levels.
2. Atomic physics-- The branch of physics which deals with the structure and
12. properties of the atom
3. Nuclear physics ---The branch of physics which deals with the structure,
properties and reaction of the nuclei of atoms.
4. Condensed matter physics ---The study of the properties of condensed
materials (solids, liquids and those intermediate between them and dense gas).
It branches into various sub-divisions including developing fields such as nano
science, photonics etc.
It covers the basics of materials science, which aims at developing new material
with better properties for promising applications.
5. High energy physics --The study of the nature of the particles.
13.
14. 1.Physics in Relation to Other Sciences
Physics is a very significant branch of science which plays a crucial role in understanding the
developments pertaining to the other branches of science such as Chemistry, Biology etc.
(i) Physics in relation to Mathematics.
Study of physical variables led to the idea of differentiation, integration and differential equation.
Meaningful interpretation of Mathematics becomes Physics.
(ii) Physics in relation to Chemistry.
The concept of X-ray diffraction and radioactivity has helped to distinguish between the various
solids and to modify the periodic table.
Understanding the bonding and the chemical structure of substances is easy with the help of the
concept of interactions between various particles.
(iii) Physics in relation to Astronomy.
Optical telescopes of reflecting and refracting type enabled man to explore the space around.
Discoveries like radio telescopes have revolutionised the study of Astronomy.
(iv) Physics in relation to Biology.
15. The conceptual study of pressure and its measurement has helped us to know blood pressure and
hence the functioning of heart.
Invention of X-rays developed the field of diagnosis.
Electron and optical microscopic designs have revolutionised the study of medical science.
(v) Physics in relation to Meteorology.
The discoveries regarding the study of pressure variations help us to forecast the weather.
Various other inventions of physics have opened new vistas of study in the field of sciences and
social sciences.
• Physics related to other sciences:
Laws of Physics are used to study different phenomenas in other sciences like
Biophysics, oceanography, seismology etc.
16. There is a large number of forces experienced or applied.
These may be macroscopic forces like gravitation, friction, contact forces.
Microscopic forces like electromagnetic and inter-atomic forces.
But all these forces arise from some basic forces called Fundamental Forces .
There are four fundamental forces which govern both macroscopic and
microscopic phenomena.
There are
(i) Gravitational force
(ii)Strong Nuclear force
(iii)Electromagnetic force
(iv)Weak Nuclear force
(v)The relative strengths of these forces are Fg : Fw : Fe : Fs = 1: : .
All those quantities which can be measured directly or indirectly and in terms of
which the laws of physics can be expressed are called physical quantities.
17. Forces of nature :--- Sir Issac Newton was the first one to give an exact definition
for force.
“Force is the external agency applied on a body to change its state of rest and
motion”.
There are four basic forces in nature.
They are gravitational force , electromagnetic force, strong nuclear force and
weak nuclear force.
Gravitational force :---
• It is the force between any two objects in the universe.
• It is an attractive force by virtue of their masses.
• By Newton’s law of gravitation, the gravitational force is directly proportional
to the product of the masses and inversely proportional to the square of the
distance between them.
• Its range is infinite.
• Gravitational force is the weakest force among the fundamental forces of
nature
18. but has the greatest large−scale impact on the universe.
Unlike the other forces, gravity works universally on all matter and energy, and is
universally attractive.
Electromagnetic force :---
It’s due to stationery or moving Electrical Charge.
It is the force between charged particles such as the force between two
electrons, or the force between two current carrying wires.
It may be attractive or repulsive . It is attractive for unlike charges and
repulsive for like charges.
The electromagnetic force obeys inverse square law.
It is very strong compared to the gravitational force.
It is the combination of electrostatic and magnetic forces.
Its range is infinite. Its stronger 1036 times than gravitational force but 10−2
times of strong Nuclear force.
Strong nuclear force :---
19. • It is the strongest of all the basic forces of nature.
• Operate between Nucleons.
• It may be attractive or repulsive.
• It, however, has the shortest range, of the order of 10−15 m.
• This force holds the protons and neutrons together in the nucleus of an atom.
• Recent discoveries show that protons and neutrons are built of elementary
particles, quarks.
Weak nuclear force :---
Weak nuclear force is important in certain types of nuclear process such as β-
decay.
10−13 times than Strong nuclear force.
Has very short range 10−15 m.
In β-decay, the nucleus emits an electron and an uncharged particle called
neutrino.
This force is not as weak as the gravitational force.
20. Name 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
This particle was first predicted by Wolfgang Pauli in 1931.
It may be attractive or repulsive.
21. Conserved Quantities----
• Physical quantities that remain constant with time are called conserved
quantities.
• Example, for a body under external force, the kinetic and potential energy
change over time but the total mechanical energy (kinetic + potential) remains
constant.
• Conserved quantities can be scalar (Energy) or vector (Total linear momentum
and total angular momentum).
Conservation Laws ---A conservation law is a hypothesis based on observation
and experiments which cannot be proved.
These can be verified via experiments.
Law of conservation of Energy ---
• According to the general Law of conservation of energy, the energies remain
constant over time and convert from one form to another.
• The law of conservation of energy applies to the whole universe and it is
22. believed that the total energy of the universe remains unchanged.
• Under identical conditions, the nature produces symmetric results at different
time.
• Energy can neither be created nor it is destroyed, however energy can be
converted from one form energy to any other form of energy
• Law of conservation of Mass---- This is a principle used in analysis of chemical
reactions.
• A chemical reaction is basically a rearrangement of atoms among different
molecules.
• If the total binding energy of the reacting molecules is less than the total
binding energy of the product molecules, the difference appears as heat and
the reaction is exothermic.
• The opposite is true for energy absorbing (endothermic) reactions.
• Since the atoms are merely rearranged but not destroyed, the total mass of
the reactants is the same as the total mass of the products in a chemical
reaction.
23. • Mass is related to energy through Einstein theory, E = mc2 , where c is the
speed of light in vacuum
Law of conservation of linear momentum ----
• Symmetry of laws of nature with respect to translation in space is termed as
law of conservation of linear momentum.
• Example law of gravitation is same on earth and moon even if the acceleration
due to gravity at moon is 1/6th than that at earth.
Law of conservation of angular momentum---
• Isotropy of space (no intrinsically preferred direction in space) underlies the
law of conservation of angular momentum.
