NCERT Solutions for Class 11 Physics Chapter 1 Physical World: Download Questions & Answers PDFs, Weightage

• What is Physics?
• Scope of Physics
• Physics, technology and Society
• Fundamental forces in nature
• Nature of physical laws

The Physical World chapter is an important chapter for the students because it forms a strong foundation for class XI students. It provides a glimpse of the scope of Physics to the students. The students can download the Physics NCERT Class 11 PDF with solutions for free.

Download Here: NCERT Solution for Class XI Physics Chapter Physical World PDF 

Q.1.1 Some of the most profound statements on the nature of science have come from Albert Einstein, one of the greatest scientists of all time. What do you think did Einstein mean when he said: “The most incomprehensible thing about the world is that it is comprehensible”?

Ans.1.1 The world is full of surprises. There are so many things happening with everyone, sometimes it becomes difficult to comprehend by us. But all the things can be explained by basic laws of sciences. Thus the incomprehensible things around us become comprehensible when we look at from scientific viewpoint.

Q.1.2 “Every great physical theory starts as a heresy and ends as a dogma”. Give some examples from the history of science of the validity of this incisive remark.

Ans.1.2 We all know that light travels in a straight line. When Huygens established his wave theory, it was a ‘heresy’. Afterwards, it became a ‘dogma’ as reflection, refraction etc. could be successfully explained on the basis of wave theory.

Initially it was believed that light was only energy but when photoelectric effect was discovered, it was proposed that light had a particle nature also. This was treated as ‘heresy’. Later on Einstein proved it by his quantum theory of light and it became a ‘dogma’.

Q.1.3 “Politics is the art of the possible”. Similarly, “Science is the art of the soluble”. Explain this beautiful aphorism on the nature and practice of science.

Ans.1.3 We are habituated with the false promises by the politicians during the elections and during their speeches; they say everything ‘possible’ to win votes. Science is the study of observation in a systematized manner. Scientists study these observations and formulate some laws, which can explain these observations irrespective of places and individuals. Force of Gravity is universal, which is applicable for every object on earth as well as in moon also. Hence it proves that science is the art of the soluble just as politics is the art of possible.

Q.1.4 Though India now has a large base in science and technology, which is fast expanding, it is still a long way from realizing its potential of becoming world leader in science. Name some important factors, which in your view have hindered the advancement of science in India.

Ans.1.4 Some of the important factors that have hindered the advancement of science in India:

• Poor infrastructure and fund
• Lack of co-ordination between Industry (consumers of scientific research) and the scientists (producers of scientific research)for the research topics
• Poor pay scale, uncertain future for the career growth, lack of motivation amongst young scientists
• Concentration of research labs in big cities deprives rural population

Q.1.5 No physicist has ever “seen” an electron. Yet, all physicists believe in the existence of electrons. An intelligent but superstitious man advances this analogy to argue that ‘ghosts’ exist even though no one has ‘seen’ one. How will you refute his argument?

Ans.1.5 Nobody has seen Air but we feel the presence of air at every moment. The constituents of air – oxygen, nitrogen etc. can be scientifically tested and proven. However the presence of ghosts or spirits cannot be scientifically proven, it exists in the imagination of superstitious people.

Q.1.6 The shells of crabs found around a particular coastal location in Japan seem mostly to resemble the legendary face of a Samurai. Given below are two explanations of this observed fact. Which of these strikes you as a scientific explanation?

(a) A tragic sea accident several centuries ago drowned a young Samurai. As a tribute to his bravery, nature through its inscrutable ways immortalized his face by imprinting it on the crab shells in that area.

(b) After the sea tragedy, fishermen in that area, in a gesture of honour to their dead hero, let free any crab shell caught by them which accidentally had a shape resembling the face of a Samurai. Consequently, the particular shape of the crab shell survived longer and therefore in course of time the shape was genetically propagated. This is an example of evolution by artificial selection.

[Note: This interesting illustration taken from Carl Sagan’s ‘The Cosmos’ highlights the fact that often strange and inexplicable facts which on the first sight appear ‘supernatural’ actually turn out to have simple scientific explanations. Try to think out other examples of this kind].

Ans.1.6 The argument (b) seems to be more logical and scientific.

Q.1.7 The industrial revolution in England and Western Europe more than two centuries ago was triggered by some key scientific and technological advances. What were these advances?

Ans.1.7 The advancement of modern science and industrial revolution always go hand in hand. The requirement of industrial revolution is always fulfilled by the new discoveries of modern science. Some of the examples are:

• Application of thermodynamics in steam engine had revolutionized the modern day transportation need
• Application of projectile motion, usage of iron and gun powder helped in development of cannons and guns. England and Western Europe conquered the rest of the world by these weapons.
• The discovery of dynamite helped in mineral exploration.

Q.1.8 It is often said that the world is witnessing now a second industrial revolution, which will transform the society as radically as did the first. List some key contemporary areas of science and technology, which are responsible for this revolution.

Ans.1.8 Some of the new-age technology which has transformed the present and has an immense potential to change the future are:

• Mobile phone technology ( 5G )
• Artificial Intelligence and Machine learning
• Biotechnology
• Nanotechnology
• 3D printing

Q.1.9 Write in about 1000 words a fiction piece based on your speculation on the science and technology of the twenty-second century.

Ans.1.9 A self-driven car arrives at a mall, passenger disembarks and the car automatically goes to the parking lot. A GPS based system guides the car to a vacant parking space. The owner enters the mall. A robot comes to the gate and greets. By scanning the face, the robot collects the data from the central database, finds out his/her nationality, food choices, medical history and shopping preferences. On the monitor fitted on the robot, he / she orders the food, groceries etc. Robot speaks in his / her mother tongue and guides to the apparel shop etc. After that another robot waits near the exit gate with the shopping trolley. The payment is done through Wi-Fi mode. The car is called through the mobile app. Robot uploads the stuff in car’s trunk and he / she drives off.

Q.1.10 Attempt to formulate your ‘moral’ views on the practice of science. Imagine yourself stumbling upon a discovery, which has great academic interest but is certain to have nothing but dangerous consequences for the human society. How, if at all, will you resolve your dilemma?

Ans.1.10 The living example is Wuhan virus. A scientist works for the benefit of mankind but when the formula falls in wrong hand, it brings a disaster. The whole world is still reeling under its harmful effect. Another example is AK-47. The designer never imagined that it could be used in this fashion, as being used by the terrorists.

Q.1.11 Science, like any knowledge, can be put to good or bad use, depending on the user.

Given below are some of the applications of science. Formulate your views on whether The particular application is good, bad or something that cannot be so clearly Categorized:

(a) Mass vaccination against small pox to curb and finally eradicate this disease from the population. (This has already been successfully done in India).

(b) Television for eradication of illiteracy and for mass communication of news and ideas.

(c) Prenatal sex determination

(d) Computers for increase in work efficiency

(e) Putting artificial satellites into orbits around the Earth

(f ) Development of nuclear weapons

(g) Development of new and powerful techniques of chemical and biological warfare).

(h) Purification of water for drinking

(i) Plastic surgery

(j ) Cloning

Ans.1.11 (a) Good. Mass vaccination has helped the entire world to completely eradicate small pox.

(b) Good. Television helps in imparting education and has helped to a great extent to spread literacy, especially in rural belt. Along with education, it also helps to keep people informed about various news and important information through various TV programs.

(c) Bad. Because it leads to female foetus killing through abortion and changes the sex ratio in human population

(d) Good. It helps to avoid repetitive work and takes care of human error.

(e) Good. For data collection, communication, surveillance etc.

(f) Bad. The misuse can lead to irreversible damages, e,g. Hiroshima-Nagasaki

(g) Bad. Chemical and Biological warfare not only destroys present generation, it causes serious harms to future generations

(h) Good. It improves health by reducing the water-borne diseases.

(i) Good - if it is used on accident victims ( e.g. acid attack), Bad – if it is used for beauty enhancement

(j) Good – if it is used for replicating good features of animals, Bad – if it used on human beings.

Q.1.12 India has had a long and unbroken tradition of great scholarship — in mathematics, astronomy, linguistics, logic and ethics. Yet, in parallel with this, several superstitious and obscurantist attitudes and practices flourished in our society and unfortunately continue even today — among many educated people too. How will you use your knowledge of science to develop strategies to counter these attitudes?

Ans.1.12 Mass awareness is the only tool. By using different communication platforms like Radio, TV, Social media, Movies etc. people can be made aware. The superstitious belief can be explained in a scientific way and they can be made aware.

Q.1.13 Though the law gives women equal status in India, many people hold unscientific views on a woman’s innate nature, capacity and intelligence, and in practice give them a secondary status and role. Demolish this view using scientific arguments, and by quoting examples of great women in science and other spheres; and persuade yourself and others that, given equal opportunity, women are on par with men.

Ans.1.13 Both men and women are of equal caliber. Since nature has given extra strength to women to bear child, they can endure immense physical and mental pain than men. Women have a keen eye for perfection, hence more and more women are being employed in present industries. Earlier the professions like fighter pilots, CEO, security personnel, cab drivers, assemblers, in factories, even football referee were believed to be male dominated, but we can see the presence of women in these fields also.

Following is the list of some of the women, who have excelled in various fields.

• Indira Gandhi
• Margaret Thatcher
• Mother Teresa
• Indra Nouie
• Kalpana Chawla

Q.1.14 “It is more important to have beauty in the equations of physics than to have them agree with experiments”. The great British physicist P. A. M. Dirac held this view. Criticize this statement. Look out for some equations and results in this book which strike you as beautiful.

Ans.1.14 One of the reasons of not so much popularity amongst masses about Physics is it is full of equations and symbols. I tend to agree with Scientist Dirac. But when one look at the simple equations, they are really beautiful. For example – W = mg, F = pA, E = mc² etc.