NCERT Solutions for Class 11 Physics Chapter 1 - Physical World

Question 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 mostincomprehensible thing about the world is that it is compreshensible” ?


The whole universe is very complex in nature because millions of phenomena are occurring simultaneously and the biological world is also very complex so the world seems to be incomprehensible i.e. as if it cannot be understood. Also we find a wide ranges of mass, length and time but, we find that we can express mass, length and time by using a few basic laws, so the physical world becomes comprehensible, hence we find that the most incomprehensible thing about the world is that it is compressible.

Question 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.


Heresy is anything against the established belief and theory which causes a few doubts in the mind of the intelligent.
Dogma is an established opinion which is questioned by a few. For example :
(i) When Galileo postulated Heliocentric theory, the Ptolemy theory of Geocentric theory ended as dogma.
(ii) The wave theory of light given by Young’s started as heresy but when it replaced by quantum theory of light given by Einstein, the wave theory ended as ‘dogma’.
(iii) It was an heresy that inertia depends upon the mass of a body but when Einstein put forwarded, mass-energy equivalence and this is dogma in Physics.

Question 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.


When a politician wins over votes he makes anything and everything possible even when he does not know anything about the problem, but on the other hand, a scientist makes a large number of observations and then come to a conclusion which is based upon certain facts and theory. Thus science is the art of soluble means that a large number of processes can be explained in terms of only a few basic concepts.

Question 4:

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


Following are some important factors, which hindered the advancement of science in India.
(i) The academic freedom is not provided to the young scientists and technologists which is essential for making advances in the fields of science and technology.
(ii) Sufficient funds are not available for science and technology.
(iii) We have bureaucratic management of science education.
(iv) There is a lack of coordination between the researchers and the industrialists. Our industrialists have little confidence in the ability of our scientists and they prefer to import technology from advanced countries.
(v) Brain drain is also major factor for the hindrance of advancement in our country.

Question 5:

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


It is true that no physicists has ever seen an electron but its existence is observed by physical experiments which proved the different shapes and sizes of molecules, flow of current etc. but there is no physical proof for the existence of “Ghosts” i.e. no experiment has ever predicted its existence. Thus these two statements are entirely different and cannot be compared.

Question 6:

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 ?


Following were the key scientific and technological advances :

  1. Discovery of electricity by designing dynamos and motors.
  2. Steam engines formed by using heat and thermodynamics.
  3. Cotton gin which separates the seeds from cotton three hundred times faster than by the hand.
  4. The discovery of explosive helped army and also for mineral exploration.
Question 7:

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 sciences and technology, which are responsible for this revolution.


Following areas can transform the present society :

  1. The development of information technology for internet, supercomputers, satellite communications.
  2. The development of superconductors at room temperature.
  3. The development of infrared detectors used for remote sensing, night vision and geological survey etc.
  4. The development in agriculture using modern techniques.
  5. The development in biotechnology, nanotechnology and genetic engineering, which will change the face of the world in coming years.
Question 8:

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


In early times, people used horses to cover long distances. Today, we can go to a place which is far away from our town by buses or cars using petrol/ diesel. For going from one country to another, we use helicopter or aeroplanes which use petrol as fuel. In twenty second century we will be able to cover distances in light years away from earth by using spacecraft without bothering about the fuel requirement. The space ship starts its journey from earth to a distant star, say 500 light years away by firing a rocket engine from the launching station. Let it may be propelled by current fed into electric motor consisting of superconducting wires so that there is no wastage of electric energy due to production of heat. When the spacecraft is out of the region of magnetic field in space, it can generate electric current by electromagnetic induction through its superconducting wires.

During its journey, let the spacecraft passes through a region which has very high temperature and it destroys the conducting properties of the electric wires of the motor of the spacecraft and the life of the astronomers in the spaceship is in danger. At this stage another spacecraft from earth station containing matter and antimatter comes to rescue of the first space ship with velocity very close to the velocity of light. Hence the first sapce ship may continue its journey to the distant star.

Question 9:

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 ?


A scientific discovery is having both the effect i.e., good or bad for human society but it always reveals a truth of nature, though there may be conflict between moral and ethical values like cleaning of animalete but this discovery can always be applied to serve mankind. Thus, all the discoveries can have good and bad effects, on mankind and the scientists must reveal the good and bad effects to the society. The discovery made today may have some dangerous effect at present but may become useful to mankind after some time. So if any discovery has great academic interest but dangerous consequence, I shall prefer to use it for academic purpose and must built up strong public opinion for its good effects and tell them not to misuse this scientific technology.

Question 10:

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 categorised :

  1. Mass vaccination against small pox to curb and finally eradicate this disease from the population (This has already been sucessfully done in India).
  2. Television for eradication of illiteracy and for mass communication of news and ideas.
  3. Prenatal sex determination
  4. Computers for increase in work efficiency
  5. Putting artificial satellites into orbits around the Earth
  6. Development of nuclear weapons
  7. Development of new and powerful techniques of chemical and biological warfare.
  8. Purification of water for drinking
  9. Plastic surgery
  10. Cloning.

(a) good (b) good (c) bad (d) good (e) good (f) bad (g) bad (h) good (i) good (j) something which cannot be so clearly categorized.

Question 11:

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 abscurantistic 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 ?


In our country, the superstitious attitudes is deeply rooted in our society and it is difficult to eradicate it. Some factors responsible for it are (i) illiteracy (ii) lack of scientific knowledge, (iii) denying of education to a large part of our society (iv) caste system etc.
Now to counter these attitudes, the knowledge of science can be used by providing mass scale education by electronic media like T.V. radio, and print media. Parents are to be encouraged to send their wards to school for education, which is the only way to understand the facts of life, and also to control the population which is the main cause of illiteracy in India.

Question 12:

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.


Though there is small difference in the anatomy and feeling of man and woman but there is no difference in the capacity of woman in intelligence, work, owning responsibility and decision-making etc. Women are more suitable for administrative and public relation work. In fact woman is not inferior to man in any sphere of activity.
There are large number of successful women in science and other spheres like Indira Gandhi, Mother Teresa, Sarojini Naidu, Margret Thatcher, Lata Mangesker, Sunita William, Kalpna Chawla etc. who have done a great job in different fields. Hence we can say that scientifically women are at par with men.

Question 13:

“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. Criticise this statement. Look out for some equations and results in this book which strike you as beautiful.


The given equation has no contradiction. Any equation in physics which agrees with experiment must be both simple and beautiful. For example massenergy relation E = mc2 is a beautiful equation. Also the equations F = ma is also simple and beautiful.

Question 14:

Though the statement quoted above may be disputed, most physicists do have a feeling that the great laws of physics are at once simple and beautiful. Some of the notable physicists, besides Dirac, who have articulated this feeling, are :
Einstein, Bohr, Heisenberg, Chandrasekhar and Feynman. You are urged to make special efforts to get access to the general books and writings by these and other great masters of physics. Their writings are truly inspiring !


Question 15:

Textbooks on science may give you a wrong impression that studying science is dry and all too serious and that scientists are absentminded introverts who never laugh or grin. This image of science and scientists is patently false. Scientists like any other group of humans, have their share of humorists, and many have led their lives with a great sense of fun and adventure, even as they seriously pursued their scientific work. Two great physicists of this genre are Gamow and Feynman.


There are other great scientists who were humorists alongwith being Physicists e.g., Homi Jahangir Bhabha, Einstein, Bohr, Dr. C.V. Raman and APJ Kalam are also a great nuclear scientists.