NCERT Solutions for Class 11 Physics Chapter 1 - Physical World

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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. The physical world is highly complex. Different orders of magnitude in space, time, and mass are involved in the complex physical world. Despite this, almost all physical occurrences can be described by a few simple laws. That is, it is possible to comprehend nature in terms of a few basic laws despite of its vast complexities. This is what Einstein meant to say.

Einstein's statement "The most inexplicable thing about the world is that it is comprehensible" takes on new meaning in this light.

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. Any opinion against the conventional belief is a heresy, while dogma is an established belief. The geocentric theory of Copernicus started as a heresy but it ended as dogma when his theory was explained by Tycho Brahe and Johnes Kepler later on.

Light travels in a straight line, which is a common observation in our daily lives. It was heresy when Huygens proposed his wave theory. However, it quickly became doctrine because interference patterns, refraction, and other phenomena could be successfully explained using wave theory.
The light was once thought to be solely energy, but when the photoelectric effect was found, it was argued that light also had a particle component, which was hotly discussed and regarded as heresy. However, Einstein's quantum theory of light was the definitive proof. It has been viewed as a dogma since then.

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. In politics, everything is possible. The politicians do not follow any principle, discipline or norm. They tend to remain in power by any means, fair or foul. But a scientist observes a phenomenon carefully and patiently, collects data, analyses it and formulates principles, thus solving the mystery of nature. Politicians will go to any length in order to gain votes. Science is a methodical examination of observations. Scientists and researchers examine these observations and develop laws based on them. Numerous natural occurrences occurring in this universe, all of which may be explained using a few basic rules. F = mg, for example, holds true for both you and me, as well as a star. Thus, in science we see that various phenomena are related, they are soluble and can be explained with similar or the same law. This goes on to justify that science is the art of the soluble just as politics is the art of the possible.

1.4 Though India now has a 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.

Ans. Here are some of the major problems that have hampered India's scientific development:

Poor pay rates and other facilities for scientists compared to administrators.
Lack of infrastructure and money for excellent research activity in science.
Talented scientists and technologists are not encouraged to pursue research work in the homeland. Instead, they prefer to migrate to developed countries where they get better salaries and research facilities.
There is a lack of coordination between researchers and industrialists. Industrialists like to borrow technology from advanced countries rather than to use indigenous technology.

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. Even though an electron has never been seen,' its effects have been observed, and its practical evidence has been verified and proven. Consider electricity. However, despite numerous reports and sightings, standardized scientific readings and proof have never been observed or satisfactorily tested in the case of spirits and ghosts. As a result, we can't say with absolute certainty that they exist.

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 immortalised 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. (a) More logical and scientific.

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. The development of contemporary science and the industrial revolution are inextricably linked. The use of Science to solve industrial issues generated public support and interest in Science, which had a significant impact on the development of modern science.

The following are some of the most important discoveries and their applications:

The use of thermodynamics and heat to create the steam engine was one of the most significant advancements in science and technology throughout the industrial revolution.
The invention of motors and dynamos was aided by the implementation and discovery of electricity. Similarly, research into gravitation led to research into motion, which led to the construction of cannons and firearms. This invention increased the amount of power in the world.

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. Here are some of the major problems that have hampered India's scientific development:

The following are some significant modern fields of technology and science that are primarily responsible for a new industrial revolution that is currently occurring and is projected to occur in the near future:

AI stands for artificial intelligence.
Computers that are extremely rapid to design.
Biotechnology
At room temperature, superconducting materials are being developed.
Electronics has progressed significantly.
Telecommunications technology
Nanotechnology is a type of technology that is used to make recent advances in the subject of space sciences.

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. In the 22nd century, humans will be able to create wormholes allowing people to travel to distant places in the universe. We will be in contact with aliens and have established human settlements outside the earth as well. With advancements in quantum Physics we shall be more aware and understanding of the true nature of our universe and existence. Our technologies will not pollute and degrade the earth. Artificial intelligence and humans could have some clashes.

In today's world, we travel to places by means of aircraft fuelled by petrol but in the twenty-second century, we may see a journey to a distant star which is located hundreds of light-years away from the earth with the help of a spaceship (which is not bounded by fuel consumption).Also, we might see the interference of aliens in our colony on other planets. Then, there might be a war for existence between humans and aliens.

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. A scientist is dedicated to discovering the truth. Every scientific breakthrough discloses a natural reality. As a result, any discovery, whether harmful or beneficial to humanity, must be made public.

However, we cannot afford to be oblivious to the repercussions. We must determine the degree of good or unfavourable repercussions before disclosing it. If we know that a specific discovery will only have dangerous effects on the general public, the discovery should be restricted to the knowledge of the scientists and researchers who are working on it. In this sense, the discovery can benefit society in the long run while not harming them right now.

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 categorised :

(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. (a) Good. Mass vaccination helped eradicate the dreaded diseases from the Earth.

(b) Good. Television helps in the literacy campaign and is an effective method of mass communication and entertainment.

(c) Bad. Prenatal sex determination is considered bad because it gives rise to the practice of abortion in the case of the female foetus.

(d) Good. Computers increase work efficiency.

(e) Good. Artificial satellites help in the worldwide communication process.

(f) Bad. Nuclear weapons if misused may cause mass destruction of mankind.

(g) Bad. These techniques may be misused for destructive purposes.

(h) Good. Purified water improves the health of people.

(i) Neither good nor bad. Plastic surgery is something which can’t be classified as either good or bad because it helps to remove a certain type of deformations in needy persons.

(j) Bad. Cloning has the potential to ruin the normal family life of human society.

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 obscurantistic 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. Mass media such as television and radio have been used to disseminate scientific explanations of daily phenomena.

The World Wide Web, Newspapers (an excellent source of information), Television (television), A radio station should be employed. Science should be taught to the general public so that they can learn about the true origins of phenomena, allowing their superstitions to fade away.

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. In terms of work, intelligence, and decision-making, there is no discernible difference between men and women. They are given equal opportunity, the female mind and physique will be just as efficient as a man's. There is a long list of exceptional women who have excelled in their fields. Some of the names are :

Madam Curie is a well-known scientist.
Indira Gandhi was the first woman to become Prime Minister of India.
Florence Nightingale was a famous nurse who lived during the Victorian era.
Margaret Thatcher was a British Prime Minister during the 1980s.

Mother Teresa, Sarojini Naidu, Kalpana Chawla are some more examples.

They come from a variety of professions, ranging from sociology to science, and they are all well-known for their contributions to society.
There might be some biological differences between men and women but that doesn't make men superior, at least not in the modern world.

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. The conviction of Dirac is correct. Equations that express full concepts and hold up against experimental results are by definition basic, compact, and symmetrical, which makes them incredibly beautiful. Beautiful equations include the following :

E = mc²,

E = hν,

F = mg

P.E. = mgh.

1.15. 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. (See the Bibliography at the end of this book.) Their writings are truly inspiring !

Ans. Physics books in general are fascinating to read. Students should seek out an excellent library in order to read some of this timeless literature. One of the books that students might suppose is Feynman's 'Surely you're joking, Mr. Feynman.' Other fascinating works are EM Rogers' Physics for the Inquiring Mind; G. Gamow's Physics, Foundations and Frontiers; G. Gamow's Thirty Years That Shook Physics; and Perelman's Physics Can Be Fun. These not only generate interest but also teaches you path-breaking laws of physics that were evolved from a very basic incident.

1.16. Textbooks on science may give you a wrong impression that studying science is dry and all too serious and that scientists are absent-minded 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. You will enjoy reading their books listed in the Bibliography.

Ans. "Scientists, like any other group of humans, have their share of humorists," as the saying goes. We can cite the example of many scientists who were fun-loving, adventurists and jovial. C.V. Raman, who enjoyed music in addition to doing serious scientific work, and Homi Jahangir Bhaba are two names that come to mind. Another e.g., Albert Einstein had the hobby of playing the violin. So apart from doing their serious work on physics they also have fun in their lifestyle. Thus the image of science and scientists is patently false which states that science is tough and boring. Students should go through the listed books of the bibliography to visualize the actual image of science and scientists.

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