NCERT Solutions for Class 11 Physics Chapter 1

Q.1 Some of the most profound statements of 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-

Since the physical world has a wide variety of things and an amazing diversity of life, it appears incomprehensible i.e. as it cannot be understood. However, on an investigation, the scientists find that the laws governing physical phenomena from atomic and astronomical ranges are few and extremely simple. In this way, the physical world becomes comprehensible. This is meant by the above statement given by Einstein.

Q.2 Every great physical theory starts as a hear say and ends as a dogma. Give some examples from the history of science of the validity of this incisive remark.

Ans-

The given statement is true. A long time ago, Ptolemy postulated that earth is stationary and all other heavenly bodies like sun, stars, planets etc. revolve around it. After that, Galileo suggested that sun is stationary and earth along with other planets is revolving around it. Galileo was punished by the authorities of that time for spreading wrong concepts. But, afterwards Galileo’s theory was supported by Newton and Kepler and now it is no more than a dogma.

Q.3 ‘Politics is the art of possible’. Similarly, ‘Science is the art of the soluble’. Explain this beautiful aphorism on the nature and practice of science.

Ans-

It is common that in order to get votes, politicians would make anything and everything possible even when they are not sure of the same. The statement that science is the art of the soluble means that a few basic concepts can be used to understand a wide variety of physical phenomena i.e. it seems as if widely different phenomena are soluble and can be explained in terms of only a few fundamental laws.

Q.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.

Some important factors which have hindered the advancement of science in India are:

i. Poverty, which gives rise to a lack of resources and lack of infrastructure

ii. Lack of education and limited facilities for higher education in science

iii. Deficiency of scientific planning

iv. Pressure of increasing population of India

v. Lack of self discipline and work culture

Q.5 No physicist has ever “seen” an atom. Yet, all physicists believe in the existence of atoms. An intelligent but superstitious man advances this analogy to argue that ‘ghosts’ exist even though no one has ‘seen’ one. How will you refute this argument?

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It is a fact that any physicist has never seen an atom. But, there is so much evidence that proves the atomic nature of matter. On the other hand, there is hardly any direct or indirect evidence to prove the existence of ghosts.

Q.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 examples 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 of 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 which accidentally had a shape resembling the shape 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-

Explanation (b) given above is a scientific explanation of the observed fact.

Q.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?

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The discovery of steam engine, blast furnace (which converts low grade iron into steel) and cotton gin (which separates the seeds from cotton three times faster than by hand) and power loom are some of the examples of key scientific and technological advances.

Q.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-

Some of the key contemporary areas of science and technology which are responsible for this revolution are:

i. Growth of superfast computers

ii. Advancements of semiconducting materials at room temperature

iii. Information explosion and development of information technology

iv. Development of digital electronics, robots and nanotechnology

v. Advancements in biotechnology

Q.9 Write in about 1000 words a fiction piece based on your speculation on the science and technology of the twenty second century.

Ans-

Imagine a space ship travelling towards a star nearly 100 light-years away. Since the space ship crosses the magnetic fields in space, it is propelled by an electric current generated by electromagnetic induction. The current is provided to an electric motor made of superconducting wires. Therefore, energy would not be required to propagate the spaceship through its entire journey.

Suppose, in a particular region of the space the temperature becomes extremely high and the superconducting property of the wires of the motor is destroyed. Since no power will be generated by the motor, it will give rise to a panic in the spaceship.

In a fraction of a second, another space ship filled with matter and antimatter stored in different compartments to generate energy for the first spaceship comes to its rescue, and the first ship continues its progressive journey.

Q.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-

If any scientific discovery is academically extremely important, then it will surely have dangerous consequences as well. Therefore, it becomes the responsibility of the scientists to inform the ordinary people about the dangerous consequences of any discovery. For example, the discovery of nuclear fusion gave rise to the production of electric power, which is very useful for mankind. On the other hand, nuclear fusion is also used for the production of an atom bomb, which can be used for the destruction of the human race. Therefore, people should be educated on large scale to use nuclear energy for peaceful purposes only.

Q.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-

a. Mass vaccination is a good application of science.

b. Television is good for eradication of illiteracy and it is a good method of mass communication and entertainment as well.

c. Since prenatal sex determination leads to the practice of abortion of female foetus, therefore, it is bad. It is creating imbalance between the male and female population, therefore, people must be educated to avoid it.

d. Computers are useful for increasing work efficiency.

e. Putting artificial satellites into orbits around the earth is good for mankind.

f. Since the development of nuclear weapons can lead to destruction of mankind, therefore, it is bad for human race.

g. Since the development of new and powerful techniques of chemical and biological warfare can lead to destruction of mankind, therefore, it is bad for human race.

h. Purification of water is useful for drinking.

i. Since plastic surgery helps to remove certain type of deformations in needy persons, therefore, it is a good application of science.

j. Cloning is a good application of science.

Q.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?

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People should be educated to eliminate superstitious and obscurantistic attitudes. It is possible with the development of the school and college curricula suitably. In this way, the teachers can take this responsibility. The mass media like radio, television, newspapers, magazines, etc. can also be very useful to educate the common people so that the superstitious and obscurantistic attitudes can be eliminated.

Q.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.

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If equal opportunity is given, women are at equality with men in every field. The basic factor responsible for the development of the human mind is the nutrition content of the prenatal and postnatal diet. The development of the human mind also depends on the care and use of the mind. Gender discrimination does not play any role in this case. Examples of great women in science and other spheres are:

Madam Marie Curie who won the Nobel Prize in Physics, Mrs. Margaret Thatcher, Mrs. Indira Gandhi, and Mrs. Bhandarnaike excelled others in politics.

Q.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 view held by the great British physicist P. A. M. Dirac is partially false. For example: E = mc²; F = ma are some of the simple equations of Physics which are having universal application as well.

On the contrary, the equations involved in some of the latest works of higher Physics and the general theory of relativity are neither simple nor beautiful. They are comparatively difficult to understand.

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.

General books on Physics make interesting reading, so the students are advised to confer a good library.

For example- ‘Mr. Feynman’ by Feynman is one of the amusing books for the students.

Some other amusing books are: Physics, Foundations and Frontiers by G. Gamow; Thirty years that shook Physics by G. Gamow; Physics for the enquiring mind by EM Rogers; Physics can be fun by Parelman.

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 Feynmann. You will enjoy reading their books listed in the Bibliography.

Scientists like other people of the human race are lively, fun loving, friendly, and adventurous people. Students are advised to go through books by the given Physicists to understand this view.