# Science | Class 11th Notes | Physics | Unit- 1. Physical World And Measurements Chapter-1 Physical WorldPart :- 2

## Scope and Excitement of Physics

Many types of physical phenomena are studied in physics.
To understand the purpose of physics, it is necessary to look at its various sub-topics.
Basically it is divided into two parts

### (1) Macroscopic (2) Microscopic

1. The macro effects of physics include earthly and astronomical level phenomena while micro physics includes atomic, natural and nuclear phenomena.

The principles of Classical Physics are used to describe macro phenomena, while quantum mechanics is used for micro phenomena.
The following are the sub-disciplines (branches) of fixed mechanics

### (i) Mechanics: In this, the laws of matter (toss, liquid and gas) are studied.

Mechanics is based on Newton's laws of motion and law of gravity.
In this, rocket propulsion, the equilibrium of the bodies and their speed are studied.
It is in this branch that mass, inertia, force, energy, strength, force - moment etc. are explained to identify the physical quantities.

(ii) Thermodynamics: The laws of thermal equilibrium of the bodies of this branch study the direction of heat flow, conversion of heat into work and changes in internal energy, heat and entropy, etc. due to heat transfer.
is .
The discovery of a heat engine is the result of a conversion to heat work.
The procedure of refrigerators is also explained under thermodynamics.

(ii) Optics: This branch considers light-based phenomena.
An interesting study of telescope, the working of microscopes, the cause of colors of various objects and thin films (such as soap bubbles), formation of rainbow etc. is done in this branch.

### (iv) Oscillations and Waves: Under this branch we vibrate different objects;

Let's study the transmission of disturbance generated by a vibrating object.
That is why we get to know how our voice moves and what are the characteristics of speech and music?

### (v) Electrodynamics: Under this branch, phenomena related to charged and magnetized objects are studied.

With this, the basic rules were laid down by Couloum, Gauss Ocited, Ampere, Laplace and Faraday etc.
Maxwell combined these rules in the form of four equations and based on this explained the transmission of electromagnetic waves.
The speed in the magnetic field of the conductor conductor, the origin of the electrical current, the transmission of radio waves in the ionosphere, etc. are studied only in electromechanical.

2. Under the microscopic influence of physics, phenomena related to atoms and nuclei are explained.
These phenomena cannot be explained by the laws of reconciled physics, modern quantum mechanics is used for this.

In this branch
In fact, physical science is the basic and stimulating science and is the basis of all the branches of science.
On the one hand in physics there is the study of many microscopic particles such as electrons, protons, atoms, molecules, etc. On the other hand there are huge celestial bodies like planets, sun, galaxy * etc.
Physics interprets natural phenomena spread from microscopic atoms to giant aerials based on leprosy facts.
Additionally, it exhibits symmetry and simplicity in virtual complexity hidden in nature.
Thus, physics is the most stimulating and challenging branch of science.
It is clear from the definition of physics that it is a constantly expanding science, which has no end.
No human can claim that he is a master of all physics.
In today's age, no person can remain separate from physics.
Some students find this topic difficult and boring but in reality it is simple and entertaining.
To understand physics, students should do experiments themselves.
Experiences of experiments are stimulating and informative and they give information about some laws of physics.
The occurrence of a current in a nearby coil caused by a moving magnet in the absence of an external source of electric carrying force prompted Faraday to give the rules for electromagnetic induction.
These rules led to the discovery of electrical generators, motors, etc.
Nowadays the events of solar eclipse, lunar eclipse, etc. are broadcast live on television, and its observations are recorded and studied later.
From these observations, the mysteries of nature are explained by the New Testament.
Radio, television, telephone, cinema, computer, all electronic devices, motors, generators, calculators, motor cars etc. are all the result of physics.
Thus in physics, the phenomena of the strange world are studied which are beneficial for living beings.

Study of  composition and structure, characteristics of basic particles (such as electrons, protons, neutrons, photons, etc.) are studied and their interactions.

For example:- with the fall of the apple and the movement of the moon, Newton formulated the famous law of gravity.

The jumping up and down the lid of the pot provided the basis for the invention of the steam engine.

Provided Galileo with a method of time measurement of oscillations of hanging lamps in the church.

The discovery of the law of floatation of Archimedes was discovered by the occurrence of water from the bath-tub.

## Nature of Physical Laws

In physics, we study the world's very small karnas(particals) (such as atoms, nuclei) and very long particles (such as stars, milky way).
Their study methods and equipment are different.
On the basis of experiments and observations, an attempt is made to find the rules as well as the rules which follow the small and long size particles.
Different physical processes are governed by different types of forces, so some physical quantities change over time.
In the process given under certain conditions, some physical quantities remain fixed over time.
The amounts that remain fixed (protected).
Protected amounts are called conserved quantities.
If we say the same with condition, then this statement is called conservation law.
Thus the conservation rule is that which shows which physical amount is protected under which condition.
Following are some conservation rules:

### 1. Conservation of Energy: If the force acting on an object is conservative, then the total mechanical energy (ie the sum of kinetic energy and potential energy) of the body remains fixed.

This is the law of conservation of mechanical energy.
The free fall of a body under gravity is an example of this.
If forces are not conserved, then the total energy of the world remains constant.
This is a comprehensive law of energy conservation.
The broad rules for energy conservation are true for all forces and all types of energy transformations.

2. Conservation of Linear Momentum: If the external force acting on a body of axes is zero, then the linear momentum of the body is preserved.
This is the law of linear momentum conservation

3. Conservation of Angular Momentum: If the external force acting on any body of the ear - momentary is zero, then the angular momentum of the body is preserved.
This is the law of angular momentum conservation.

4. Mass - Energy Conservation: According to Einstein, mass and energy are not separate physical quantities, but two forms of the same amount.
Mass can be converted into energy and energy into mass.
The equivalent relationship between mass and energy is E = mc2, in which E (in joules) is energy and m (in kilograms) is mass.
According to this, if energy E is dissipated, mass m increases and if mass m is destroyed, energy E is generated.

#### For example:- in a nuclear reaction, the total number of nucleons (protons + neutrons) is fixed, whereas the total mass of nuclei acting in the process, before and after action, is not fixed, but there is a slight difference.

goes ;
This difference is called mass defect.
It manifests as mass - damage energy.
Thus, the law of conservation of mass mass-energy is that the sum of the entire mass and energy of the world (both in the same unit) is preserved.

## Physics: Technology and Society

Physics is a friend of all branches of science and it has an important contribution in the development of all branches of science and the upliftment of society.

### Physics and Technology

The experimental aspect of physics has contributed significantly to the development of craft technology.
The conversion of heat by Joule and the discovery of electromagnetic induction by Faraday not only benefited society but also laid the foundation of technology.
Following are some examples of the impact of physics on technology:

(i) Design of many machines were prepared by studying lever system.
(ii) The study of air flow was discovered by air flow.
(iii) The discovery of conversion to heat work led to the invention of a heat engine.
(iv) The study of semiconductors, union diodes and transistors made it possible to manufacture radio, television, computers and robots.
(v) The study of nuclear fission made possible the manufacture of nuclear furnace and atomic bomb.
(vi) The study of nuclear fusion made hydrogen bombs possible.
(vii) The study of x-rays made the manufacture of x-ray machine possible.
This machine has great importance in medical science.
(viii) Treatment of cancer by the study of laser and the tips of removing stones from the kidneys and gall bladder.
Construction was possible.

Thus it is clear that the modern development of physics made many improvements in technology and heralded the industrial revolution.