NCERT Solutions for Class 11th: Chapter 1 Physical World Physics Science
6 Jan 2017
NCERT Solutions for
Class 11th: Chapter 1 Physical World Physics Science
The National Council of Educational Research and Training (NCERT) is an autonomous organisation of the Government of India that was established on 1 September 1961 as a literary, scientific and charitable Society under the Societies' Registration Act (Act XXI of 1860).
NCERT Solutions for
Class 11th: Chapter 1 Physical World Physics Science
The National Council of Educational Research and Training (NCERT) is an autonomous organisation of the Government of India that was established on 1 September 1961 as a literary, scientific and charitable Society under the Societies' Registration Act (Act XXI of 1860).
The National Council of Educational Research and Training (NCERT) is an autonomous organisation of the Government of India that was established on 1 September 1961 as a literary, scientific and charitable Society under the Societies' Registration Act (Act XXI of 1860).Exercises
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”?
Answer
The Physical world around us is full of different complex natural phenomena so the world is in-comprehensible. But with the help of study and observations it has been found that all these phenomena are based on some basic physical laws and so it is comprehensible.
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.
Answer
The statement above is true. Validity of this incisive remark can be validated from the example of moment of inertia. It states that the moment of inertia of a body depends on its energy. But according to Einstein's mass-energy relation (E = mc2), energy depends on the speed of the body.
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.
Answer
It is well known that to win over votes, politicians would make anything and everything possible even when they are least sure of the same. and in Science the various natural phenomena can be explained in terms of some basic laws. So as 'Politics is the art of possible' similarly 'Science is the art of the soluble'.
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 a world leader in science. Name some important factors, which in your view have hindered the advancement of science in India.
Answer
Some important factors in our view which have hindered the advancement of science in India are:
→ Proper funds are not arranged for the development of research work and laboratories. The labs and scientific instruments are very old and outdated.
→ Most of the people in India are uneducated and highly traditional. They don't understand the importance of Science.
→ There is no proper employment opportunity for the science educated person in India.
→ There are no proper facilities for science education in schools and colleges in India.
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?
Answer
No physicist has ever seen an atom but there are practical evidences which prove the presence of electron. Their size is so small, even powerful microscopes find it difficult to measure their sizes. But still its effects could be tested
On the other end there is no phenomena which can be explained on the basis of existence of ghosts.
Our senses of sight and hearing are very limited to observe the existence of both.
So there is no comparison between the two given cases.
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 honor 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].
(b) After the sea tragedy, fishermen in that area, in a gesture of honor 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].
Answer
Explanation (b) is correct is a scientific explanation of the observed fact.
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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 ?
Answer
More than two centuries ago, England and Western Europe invented steam engine, electricity, theory of gravitation and the explosives. Steam engines helped them in the field of hat and thermodynamics, theory of gravitation in field of motion and making guns and cannons. These progresses brought about industrial revolution in England and Western Europe.
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.
Answer
Some of the key contemporary areas of science and technology which may transform the society radically are:
→ Development of super fast computers
→ Internet and tremendous advancement in information technology
→ Development in Biotechnology
→ Development of super-conducting materials at room temperature.
→ Dvelopment of robots.
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?
Answer
In our view a type of discovery which is of great academic interest but harmful for human society should not be made public because Science is for the society, society is not for science.
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).
► Good
(b) Television for eradication of illiteracy and for mass communication of news and ideas.
► Good
(c) Prenatal sex determination
► Bad
(d) Computers for increase in work efficiency
► Good
(e) Putting artificial satellites into orbits around the Earth
► Good
(f ) Development of nuclear weapons
► Bad
(g) Development of new and powerful techniques of chemical and biological warfare).
► Bad
(h) Purification of water for drinking
► Good
(i) Plastic surgery
► Good
(j ) Cloning
(You can use your own prespective for answering above questions)
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 ?
Answer
Answer
Some people in our society have the view that women do not have the innate nature, capacity and intelligence.
To demolish this view there are many examples of women who have proven their abilities in Science and other fields.
Madam Curie, Mother Teresa, Indira Gandhi, Marget Thatcher, Rani Laxmi Bai, Florence Nightingale are some examples. So in this era women are definitely not behind man in any field.
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.
Answer
An equation which agrees with experiment must also be simple and hence beautiful. We have some simple and beautiful equations in Physics such as
→ E = mc2 (Energy of light)
→ E = hv (Energy of a photon)
→ KE = 1/2mv2(Kinetic energy of a moving particle)
→ PE = mgh (Potential energy of a body at rest)
→ W = F.d (Work done)
All have the same dimensions. One experiment shows dependency of energy on speed, the other shows dependency on frequency & displacement.
That's the beauty of equations in Physics coming from different experiments.