Physics Class 11 Chapter 1 Notes - Physical World

SectionA – (1 Mark Questions)

1. Name that branch of science that deals with the study of Earth.

Ans. Geology

2. Name that branch of science that deals with the study of stars.

Ans. Astronomy.

3. Name Indian-born scientist who received Nobel Prize for his discoveries in astronomy.

Ans. S. Chandra Shekhar.

4. What is the meaning of the verb ‘Scientia’? 

Ans. To ‘know’

5. Who discovered the electron? What is an electron?

Ans. J.J. Thomson

Section – B (2 Marks Questions)

6. 

(a) Name a great scientist who gave the following comment on science.

“Science is not just a collection of laws, a catalog of unrelated facts. It is a creation of the human mind, with its freely invented ideas and concepts.”

(b) Which famous philosopher gave the following comments on science?

“We know very little and yet it is astonishing that we know so much, and still more astonishing that so little knowledge of science can give so much power.”

Ans. 

(a) Albert Einstein.

(b) Bertrand Russel

7. Name the scientist and the country of his origin who received the Nobel Prize for his work on molecular spectra. 

Ans. C.V. Raman, India.

8. Name four physics devices widely used in medical diagnosis.

Ans. (i)  Direction X-rays,

(ii) Ultrasound,

(iii) Stethoscope,

(iv) Microscope.

9.Name the scientist and the country of his origin whose field of work was elasticity.

Ans. Robert Hook, England

10. What are Physical Sciences? Give a few examples?

Ans. They are defined as the sciences which deal with non-living things, 

e.g. Physics, Chemistry, Astronomy, Astrology, Geology, Geography, Oceanology.

PDF Summary - Physics Class 11 Chapter 1 Notes on the Physical World

Science and its origin:

Science can be defined as a systematic understanding of natural phenomena in a very detailed manner so that we can predict, control and modify it. Science is all about experimenting and exploring speculating phenomena occurring around us.

• The term Science has been originated from a Latin verb Scientia which means ‘to know’.

• Scientific method can be called as a method to acquire knowledge in a systematic and in-depth way. It is having:

• Systematic observations

• Controlled experiments

• Qualitative and Quantitative reasoning

• Mathematical modelling

• Prediction and verification (or falsification) of theories

• Speculation or Prediction

• Science will be not having any final theory. The observations which are made using improved, accurate tools will be creating improved knowledge and perspective. Tycho Brahe’s research on planetary motion has been used by Johannes Kepler for improving Nicolas Copernicus theory.

• Quantum mechanics was developed in order to deal with atomic and nuclear phenomena. Work of Ernest Rutherford on nuclear model of atom made the basis of quantum theory suggested by Niels Bohr. The discovery of antielectron (positron) was led by the Antiparticle theory of Paul Dirac by Carl Anderson.

Natural Sciences:

Natural science can be considered as a branch of science which is discussing about the description, prediction, and understanding of the natural phenomena which is on the basis of an observational and empirical evidence. It will be included of the disciplines mentioned below:

• Physics

• Chemistry

• Biology

Physics:

Physics can be defined as a study of the basic laws of nature and their usage in various natural phenomena. Physics can be called the study of the physical world and matter and its movement through space and time, along with connected concepts like energy and force.

• Word Physics has been originated from a 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 is a method for deriving characteristics of complex systems from the properties and interaction of its 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).

Effect and uses of Physics:

• We can describe a phenomena occurring over a bigger magnitude using a simple theory.

• We can use the experiments and observations for developing new theories in the case of unidentified phenomena and make improvement for old theories in the existing phenomena.

• We can develop devices by the use of physics laws.

Scope of Physics:

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

Physics can be categorised broadly into two kinds on the basis of its scope - Classical Physics and Modern Physics. Classical physics is a branch which is dealing with macroscopic phenomena while modern physics will be dealing with microscopic phenomena.

Macroscopic Domain:

The macroscopic domain is having phenomena’s involved at large scales such as laboratory, terrestrial and astronomical.  It will be including subjects listed below:

1. Mechanics – This is a branch on the basis of Newton’s laws on motion and gravitational laws. It will be related to the motion/equilibrium of particles, rigid and deformable bodies and the general system of particles.

Examples are listed below:

a. Propulsion of rocket using the ejecting gases

b. Water or Sound waves

c. Under a load, a bent rod is in equilibrium.

2. Electrodynamics is a branch which is involved with electric and magnetic phenomena related with charged and magnetic bodies. Here are some examples for it:

a. Movement of a current-carrying conductor in a magnetic field

b. The response of a circuit to an ac voltage (signal)

c. The generation of radio waves in the ionosphere

3. Optics – This branch is discussing about the natural processes involving light. The examples will be,

a. Reflection and refraction of light

b. Dispersion of light through a prism

c. Colour shown by thin films

4. Thermodynamics is a branch with systems in macroscopic equilibrium and varies in internal energy, temperature, entropy and so on , of systems under the application of the external force or heat. Examples are,

a. The efficiency of heat engines

b. Direction of physical and chemical process

Microscopic Domain

The microscopic domain will be processed at small scales such as atomic, molecular and nuclear. It will be discussing the interaction of probes such as electrons, photons and other elementary particles. Quantum theory has been made to discuss these phenomena.

There are some reasons for the improvement of Physics

• Qualitative analysis along with quantitative analysis.

• Universal laws are applicable in various contexts.

• Approximation approach (complex phenomena broken down into a collection of basic laws).

• Extracting and focusing on necessary characteristics of a phenomenon.

Hypothesis, Axiom and Models:

a) Hypothesis can be defined as an act of supposing without assuming that it is correct. It cannot be proven although can be verified by the use of a series of experiments.

b) Axiom will be a self-evident truth that it is acceptable by not having any question or controversy.

c) Model can be defined as a theory put forward for describing the observed phenomena.

d) Assumption can be defined as the basis of physics. Using this, a huge number of phenomena are being explained. These assumptions are created from experiments, observation and a huge number of statistical data.

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 got invented during the industrial revolution in the eighteenth century.

• Development of wireless communication after the discovery of laws of electricity and magnetism.

• Neuron-induced fission of uranium, attempted by Hahn and Meitner in 1938, showed to the formation of nuclear power reactors and nuclear weapons.

• Electricity has been produced from solar, wind, geothermal etc. energy.

Fundamental Forces in Nature:

The forces which is visible in our daily life such as muscular, friction, forces due to compression and change in length of strings and springs, fluid and gas pressure, magnetic, electric, interatomic and intermolecular forces are derived forces since their originations are because of a few fundamental forces in nature.

These fundamental forces are as mentioned below:

1. Gravitational Force ca be defined as a force of mutual attraction between any two objects because of their masses. This has been considered as a universal force since every object is feeling this force because of every other object in the universe.

2. Electromagnetic Force can be called as a force existing between charged particles. Charges at rest is having electric attraction which is visible between unlike charges and repulsion which is between like charges. Charges in motion will be creating magnetic force. Together they are known as Electromagnetic Force.

3. Strong Nuclear Force is an attractive force found in between protons and neutrons in a nucleus. It is charge-independent and is acting equally between a proton and a proton, a neutron and a neutron, and a proton and a neutron. According to the latest discoveries, the protons and neutrons are made up of elementary particles known as quarks.

4. Weak Nuclear Force can be defined as a force that appear only in specific nuclear processes like the β-decay of a nucleus. In β-decay, the nucleus will be emitting an electron and an uncharged particle called known as the neutrino. In 1931, this particle has been predicted for the first time by Wolfgang Pauli.

Table drawn below is representing the difference between the above forces.

5. Unification of Forces: So many physicists tried for combining a few of the above fundamental forces. It has been shown in a table below.

Conserved Quantities:

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

• Physical quantities will be held fixed with time 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 to 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.

• The nature develops symmetric results at 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 theory, $\text{E=m}{{\text{c}}^{\text{2}}}$, 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 at moon is ${{\frac{\text{1}}{\text{6}}}^{\text{th}}}$than that at 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.

Physics Chapter 1 Physical World Class 11 Notes – An Overview

Class 11 Physics Notes Chapter 1 PDF are prepared by well experienced CBSE teachers keeping in mind the present syllabus. These notes are the best pieces to study and clear your concepts regarding the evolution of sciences over many years. Students become familiar with their surroundings, objects, movements, forces, and also mathematics.

Vedantu provides the best Class 11 Physics Chapter 1 Physical World notes PDF for free that will help students reduce their stress during exams. Class 11 could be a turning phase in a student’s life as it brings a vast syllabus to cover that too with clear understanding. These Class 11 ch 1 Physics notes will help them prepare for board examinations in a better way.

What are the Different Concepts Covered in Physics Class 11 Chapter 1 Notes?  

Class 11 ch 1 physics notes provide a basic understanding of the different phenomena to study in Physics. However, going through the entire chapter while preparing for exams could be difficult and time-consuming. It is better to prefer to prepare and have a basic understanding through physical world notes. 

Below Are the Basic Concepts That Are to Be Covered in the Physics Class 11 Chapter 1 Notes:

• Physics

• Basic Principal approaches in Physics to follow

• Scope of Physics in future

• Society and Advancing Technology

• Forces, their laws, description on the daily life forces like gravitational forces, nuclear forces, electromagnetic forces, etc

• Conservation laws

CBSE Physics Chapter 1 Physical World Class 11 Notes

Beginning with the very first topic to be covered in the Physics Chapter 1 physical world Class 11 notes:

Physical World

Physical World defines the complexity that you face in nature. Thus if you try to solve these complexities, it will bring you to the new physical world. In general, you will define the physical world as the analysis done on nature, which states how the world is around us.

How Will You Define Physics?

The meaning of Physics is Nature. Aristotle discovered this concept in 350 BC, which is today fundamental to all other science subjects. Physics is the science which deals with surroundings, nature, and natural phenomena. You will also understand why apples are falling towards earth, why days and nights are formed, how seasons change in a year, the concept of winds, and much more. This subject is never-ending.

What are Science and Scientific Methods?

Science is the study to acquire knowledge about your surroundings. Your observations, experiments, and verifications will decide how you gain knowledge from your surroundings.

Scientific Methods include several interrelated concepts. The various steps include reasoning, systematic observations, theoretical prediction, and mathematical modelling.

What is the Scope of Physics? 

Physics is a vast concept with a broad scope. You will have basic knowledge of mass, weight, length, time, energy, and many other concepts.

The study of physics also deals with the universe and galaxies. In microscopic concept, it deals with the nucleus of an atom. It widely covers a set of nature rules and natural occurrences. Dealing with physics is like a challenge to carry out our imaginations and perform new experiments for inventing new things. It is a fascinating concept.

Relation of Physics to Other Subjects

Ealing with physics is very significant as it leads to the development of other science subjects.

• Physics with Mathematics: It is the world of physics that deals with integration, differentiation, and the differential equation. If we interpret mathematics into a meaningful form, it becomes physics. 

• Physics with Chemistry: The concept of radioactivity, X-Ray was before in Physics. However, in chemistry, it is used to distinguish different substances and modify the periodic table. 

• Physics with Astronomy: The study about optical telescopes that reflect and refract the light rays has brought up astronomy.

• Physics with Biology: The concept of pressure deals with knowledge of blood pressure and its measurement. Hence functioning of the heart is also a concept of physics. X-Rays helped in the diagnosis of the problem in an animal body.

• Physics with Meteorology: With the concept of pressure, you understand the weather forecasting techniques. 

Society and Advancing Technology

With the new inventions, it has led to advancement in technology. With rising technology, it has brought new concepts to understand in physics. The development of technology relates closely to science and applied physics.  Thus, human minds have developed better in different fields, including communication, laser making blood surgery, transportation, and many other fields. 

Forces in Nature

For basic physics understanding, you need to deal with four fundamental forces:

• Gravitational

• Electromagnetic

• Nuclear Forces

• Weak Forces

Conservation Laws

The concept of conservation laws become easy with mass conservation. Suppose you have a ball, you divide it into two pieces or many. The mass of the ball and the total mass of the pieces remains the same always. This is the conservation of mass.

Important Questions for Class 11 Physics Chapter 1

1. State the law of conservation of energy.

2. State the law of conservation of angular momentum.

3. Explain in brief the relationship of  Physics to Chemistry.

4. What did Einstein mean when he said that “The most incomprehensible thing about the world is that it is comprehensible”?

5. What are the two advancements made in technology on the basis of Physics?

6. Explain briefly the relationship of Physics to Biological Science.

7. Explain the following briefly:

• Mechanism

• Thermodynamics

• Relativity

• Electromagnetism

8. Illustrate the beauty of Scientific Theory with an example.

9. What did Einstein mean when he said “The most incomprehensible thing about the world is that it is comprehensible”?

10. Explain the fundamental force of nature.

Physical World Chapter-Related Important Study Materials

It is a curated compilation of relevant online resources that complement and expand upon the content covered in a specific chapter. Explore these links to access additional readings, explanatory videos, practice exercises, and other valuable materials that enhance your understanding of the chapter's subject matter.

Conclusion

The Physics Class 11 Chapter 1 Notes on the Physical World by Vedantu provides a fundamental overview of the subject. The key takeaway is understanding the essence of physics in our daily lives and the exploration of the natural world. Focus on grasping foundational concepts like measurements, units, and the scientific method. Emphasize the significance of precision in measurements and the role of experimentation in validating theories. Additionally, pay attention to the historical development of physics, acknowledging the contributions of notable scientists. To excel, concentrate on building a strong foundation for future chapters by mastering these essential principles.

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